| 1. |
- Karimi, Mohammad Taghi, et al.
(författare)
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Evaluation of the hip joint contact force in subjects with Perthes based on OpenSIM
- 2019
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Ingår i: Medical Engineering and Physics. - : Elsevier. - 1350-4533 .- 1873-4030. ; 67, s. 44-48
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Tidskriftsartikel (refereegranskat)abstract
- The head of femoral bone is deformed in the subjects with Leg Calve Perthes disease (LCPD). This may be due to the excessive loads applied on it. There are no studies that report the hip joint contact force in subjects with LCPD. Therefore, the aim of this study was to evaluate the hip joint contact force in subjects with Perthes disease. Ten typically-developing (TD) children and 10 children with LCPD were recruited in this study. The kinematics and kinetics of the subjects were evaluated in 3D motion analysis. The hip joint contact force was approximated using OpenSIM software. Differences were determined with an independent t-test. There was a significant difference between walking speed of TD and Perthes subjects (63.8 (±8.1) and 57.4 (±7.0) m/min, respectively). The first peak of hip joint contact force was 4.8 (±1.7) N/BW in Perthes subjects, compared to 7.6 (±2.5) N/BW in TD subjects (p = 0.004). The peak hip joint contact force in mediolateral and anteroposterior directions was significantly lower in Perthes subjects (p < 0.05). The hip joint excursion was 40.0 (±5.6) and 46.4 (±8.5) degrees in Perthes and normal subjects, respectively (p = 0.03). The hip joint contact forces were lower in the subjects with Perthes disease. Therefore, it can be concluded that the strategies used by LCPD subjects were successful to decrease hip joint contact force.
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| 2. |
- Bartonek, Asa, et al.
(författare)
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Head and Trunk Movements During Turning Gait in Children with Cerebral Palsy
- 2019
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Ingår i: Journal of motor behavior. - : ROUTLEDGE JOURNALS, TAYLOR & FRANCIS LTD. - 0022-2895 .- 1940-1027. ; 51:4, s. 362-370
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Tidskriftsartikel (refereegranskat)abstract
- Thirty children with cerebral palsy (CP) and 22 typical developing (TD) were tested with 3D-gait analysis. At turning, trunk rotation was larger in CP2 (GMFCS II) than in TD and CP1 (GMFCS I), and head flexion was larger in CP3 (GMFCS III) than TD. Maximum head and trunk flexion values during the entire trial were larger in CP3 than in the other groups, and trunk flexion was larger in CP2 than in TD. Trial time increased with GMFCS-level. Less trunk rotation than TD and CP1 reflects spatial insecurity in CP2, which in CP3 is compensated by the walker. The flexed head and trunk in CP3 and trunk in CP2 may reflect deficits in proprioception and sensation requiring visual control of the lower limbs.
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| 3. |
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| 4. |
- Engström, Pähr, et al.
(författare)
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Botulinum toxin A does not improve cast treatment for idiopathic toe-walking - a randomized controlled trial
- 2013
-
Ingår i: Journal of Bone and Joint Surgery. American volume. - 0021-9355 .- 1535-1386. ; 95:5, s. 400-407
-
Tidskriftsartikel (refereegranskat)abstract
- Background: There are many treatments for idiopathic toe-walking, including casts with or without injection of botulinum toxin A. Combined treatment with casts and botulinum toxin A has become more common even though there have been few studies of its efficacy and safety problems. Our aims were to conduct a randomized controlled trial to test the hypotheses that combined treatment with casts and botulinum toxin A is more effective than casts alone in reducing toewalking by patients five to fifteen years of age, and that the treatment effect correlates with the extent of coexisting neuropsychiatric problems. Methods: All patients who had been consecutively admitted to the pediatric orthopaedics department of our institution because of idiopathic toe-walking between November 2005 and April 2010 were considered for inclusion in the study. Forty-seven children constituted the study population. The children were randomized to undergo four weeks of treatment with below-the-knee casts either as the sole intervention or to undergo the cast treatment one to two weeks after receiving injections of botulinum toxin A into the calves. Before treatment and three and twelve months after cast removal, all children underwent three-dimensional (3-D) gait analysis. The severity of the idiopathic toe-walking was classified on the basis of the gait analysis, and the parents rated the time that their child spent on his/her toes during barefoot walking. Passive hip, knee, and ankle motion as well as ankle dorsiflexor strength were measured. Before treatment, all children were evaluated with a screening questionnaire for neuropsychiatric problems. Results: No differences were found in any outcome parameter between the groups before treatment or at three or twelve months after cast removal. Several gait-analysis parameters, passive ankle motion, and ankle dorsiflexor strength were improved at both three and twelve months in both groups, even though many children still demonstrated some degree of toe-walking. The treatment outcomes were not correlated with coexisting neuropsychiatric problems. Conclusion: Adding botulinum toxin-A injections prior to cast treatment for idiopathic toe-walking does not improve the outcome of cast-only treatment. Level of Evidence: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.
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| 5. |
- Engström, Pähr, et al.
(författare)
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Does Botulinum toxin A improve the walking pattern in children with idiopathic toe-walking?
- 2010
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Ingår i: Journal of Children's Orthopaedics. - : SAGE Publications. - 1863-2521 .- 1863-2548. ; 4:4, s. 301-308
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Tidskriftsartikel (refereegranskat)abstract
- Background: Numerous recommendations have been made for treating idiopathic toe-walking (ITW), but the treatment results have been questioned. The purpose of this study was to investigate whether botulinum toxin A (BTX) improves the walking pattern in ITW as examined with 3-D gait analysis. Participants and methods: A consecutive series of 15 children (aged 5-13 years) were enrolled in the study. The children underwent a 3-D gait analysis prior to treatment with a total of 6 units/kg bodyweight Botox® in the calf muscles and an exercise program. The gait analysis was repeated 3 weeks and 3, 6, and 12 months after treatment. A classification of toe-walking severity was made before treatment and after 12 months. The parents rated the perceived amount of toe-walking prior to treatment and 6 and 12 months after treatment. Results: Eleven children completed the 12-month follow-up. The gait analysis results displayed a significant improvement, indicating decreased plantarflexion angle at initial contact and during swing phase and increased dorsiflexion angle during midstance at all post-treatment testing instances. According to the parents' perception of toe-walking, 3/11 children followed for 12 months had ceased toe-walking completely, 4/11 decreased toe-walking, and 4/11 continued toe-walking. After 6-12 months, the toe-walking severity classification improved in 9 of the 14 children for whom data could be assessed. Conclusions: A single injection of BTX in combination with an exercise program can improve the walking pattern in children with ITW seen at gait analysis, but the obvious goal of ceasing toe-walking is only occasionally reached.
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| 6. |
- Eriksson, Marie, et al.
(författare)
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Gait pattern in children with arthrogryposis multiplex congenita
- 2010
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Ingår i: Journal of Children's Orthopaedics. - : SAGE Publications. - 1863-2521 .- 1863-2548. ; 4:1, s. 21-31
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Lower limb contractures and muscle weakness are common in children with arthrogryposis multiplex congenita (AMC). To enhance or facilitate ambulation, orthoses may be used. The aim of this study was to describe gait pattern among individuals wearing their habitual orthotic devices. Methods: Fifteen children with AMC, mean age 12. 4 (4. 3) years, with some lower limb involvement underwent 3-D gait analysis. Three groups were defined based on orthosis use; Group 1 used knee-ankle-foot orthoses with locked knee joints, Group 2 used ankle-foot orthoses or knee-ankle-foot orthoses with open knee joints and Group 3 used no orthoses. Results: The greatest trunk and pelvis movements in all planes and the greatest hip abduction were observed in Group 1, compared to Groups 2 and 3, as well as to the gait laboratory control group. Maximum hip extension was similar in Groups 1 and 2, but in Group 3, there was less hip extension and large deviations from the control data. Lower cadence and walking speed were observed in Group 1 than in Groups 2 and 3. The step length was similar in all groups and also with respect to the gait laboratory reference values. Conclusions: Children with AMC were subdivided according to orthoses use. Kinematic data as recorded with 3-D gait analysis showed differences among the groups in trunk, pelvis and knee kinematics, and in cadence and walking speed. The step length was similar in all groups and to the gait laboratory reference values, which may be attributable to good hip extension strength in all participants.
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| 7. |
- Forslund, Emelie Butler, et al.
(författare)
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A Protocol for Comprehensive Analysis of Gait in Individuals with Incomplete Spinal Cord Injury
- 2024
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Ingår i: Methods and Protocols. - : MDPI AG. - 2409-9279. ; 7:3
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Tidskriftsartikel (refereegranskat)abstract
- This is a protocol for comprehensive analysis of gait and affecting factors in individuals with incomplete paraplegia due to spinal cord injury (SCI). A SCI is a devastating event affecting both sensory and motor functions. Due to better care, the SCI population is changing, with a greater proportion retaining impaired ambulatory function. Optimizing ambulatory function after SCI remains challenging. To investigate factors influencing optimal ambulation, a multi-professional research project was grounded with expertise from clinical rehabilitation, neurophysiology, and biomechanical engineering from Karolinska Institutet, the Spinalis Unit at Aleris Rehab Station (Sweden's largest center for specialized neurorehabilitation), and the Promobilia MoveAbility Lab at KTH Royal Institute of Technology. Ambulatory adults with paraplegia will be consecutively invited to participate. Muscle strength, sensitivity, and spasticity will be assessed, and energy expenditure, 3D movements, and muscle function (EMG) during gait and submaximal contractions will be analyzed. Innovative computational modeling and data-driven analyses will be performed, including the identification of clusters of similar movement patterns among the heterogeneous population and analyses that study the link between complex sensorimotor function and movement performance. These results may help optimize ambulatory function for persons with SCI and decrease the risk of secondary conditions during gait with a life-long perspective.
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| 8. |
- Gutierrez-Farewik, Elena, 1973-
(författare)
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Botulinum toxin A does not improve cast treatment for idiopathic toe-walking-a randomized controlled trial
- 2013
-
Ingår i: Journal of Bone and Joint Surgery. American volume. - 0021-9355 .- 1535-1386. ; 95:5, s. 400-407
-
Tidskriftsartikel (refereegranskat)abstract
- ACKGROUND:There are many treatments for idiopathic toe-walking, including casts with or without injection of botulinum toxin A. Combined treatment with casts and botulinum toxin A has become more common even though there have been few studies of its efficacy and safety problems. Our aims were to conduct a randomized controlled trial to test the hypotheses that combined treatment with casts and botulinum toxin A is more effective than casts alone in reducing toe-walking by patients five to fifteen years of age, and that the treatment effect correlates with the extent of coexisting neuropsychiatric problems.METHODS:All patients who had been consecutively admitted to the pediatric orthopaedics department of our institution because of idiopathic toe-walking between November 2005 and April 2010 were considered for inclusion in the study. Forty-seven children constituted the study population. The children were randomized to undergo four weeks of treatment with below-the-knee casts either as the sole intervention or to undergo the cast treatment one to two weeks after receiving injections of botulinum toxin A into the calves. Before treatment and three and twelve months after cast removal, all children underwent three-dimensional (3-D) gait analysis. The severity of the idiopathic toe-walking was classified on the basis of the gait analysis, and the parents rated the time that their child spent on his/her toes during barefoot walking. Passive hip, knee, and ankle motion as well as ankle dorsiflexor strength were measured. Before treatment, all children were evaluated with a screening questionnaire for neuropsychiatric problems.RESULTS:No differences were found in any outcome parameter between the groups before treatment or at three or twelve months after cast removal. Several gait-analysis parameters, passive ankle motion, and ankle dorsiflexor strength were improved at both three and twelve months in both groups, even though many children still demonstrated some degree of toe-walking. The treatment outcomes were not correlated with coexisting neuropsychiatric problems.CONCLUSION:Adding botulinum toxin-A injections prior to cast treatment for idiopathic toe-walking does not improve the outcome of cast-only treatment.TRIAL REGISTRATION: ClinicalTrials.gov NCT01590693.
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| 9. |
- Gutierrez Farewik, Elena M, 1973-
(författare)
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A new model for diffuse brain injury by rotational acceleration: II. Effects on extracellular glutamate, intracranial pressure, and neuronal apoptosis
- 2001
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Ingår i: Journal of Neurotrauma. - 0897-7151 .- 1557-9042. ; 18:3, s. 259-73
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study is to monitor excitatory amino acids (EAAs) in the extracellular fluids of the brain and to characterize regional neuronaldamage in a new experimental model for brain injury, in which rabbits were exposed to 180-260 krad/s2 rotational head acceleration. This loading causes extensive subarachnoid hemorrhage, focal tissue bleeding, reactive astrocytosis, and axonal damage. Animals were monitored for intracranial pressure (ICP) and for amino acids in the extracellular fluids. Immunohistochemistry was used to study expression of the gene c-Jun and apoptosis with the terminal deoxynucleotidyl transferase nick-end labeling (TUNEL) technique. Extracellular glutamate, glycine, and taurine increased significantly in the hippocampus within a few hours and remained high after 24 h. Neuronal nuclei in the granule layers of the hippocampus and cerebellum were positive for c-Jun after 24 h. Little immunoreactivity was detected in the cerebral cortex. c-Jun-positive neuronal perikarya and processes were found in granule and pyramidal CA4 layers of the hippocampus and among the Purkinje cells of the cerebellum. Also some microglial cells stained positively for c-Jun. TUNEL reactivity was most intense at 10 days after trauma and was extensive in neurons of the cerebral cortex, hippocampus, and cerebellum. The initial response of the brain after rotationalhead injury involves brain edema after 24 h and an excitotoxic neuronal microenvironment in the first hour, which leads to extensive delayed neuronal cell death by apoptosis necrosis in the cerebral cortex, hippocampus and cerebellum.
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| 10. |
- Kizyte, Asta, 1993-
(författare)
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High-Density Electromyography-Based Methods for Joint Torque Prediction and Motor Unit Behavior Observation
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Electromyography (EMG) is a technique that measures the electrical activity of muscles. It reflects muscle activation and provides an interface to the central nervous system at the level of the muscle or individual motor units, which helps us understand the mechanisms of muscle force production, control, and coordination. EMG can also be used to detect changes in muscle activity caused by pathology, making it a valuable tool for research, diagnosis, and rehabilitation. One of the latest advancements in EMG technology is high-density EMG (HD-EMG). HD-EMG measures multiple spatially separated samples of muscle activation. This additional spatial information in HD-EMG offers new possibilities for the prediction of joint torques and the ability to look into individual motor units by decomposing the signals using blind source separation methods. This thesis presents two studies that explore the use of HD-EMG methods for joint torque estimation and the observation of motor unit behavior. In the first paper, we presented a detailed investigation of the effects of different EMG and kinematic inputs on the accuracy and robustness of ankle joint torque prediction using support vector regression. To evaluate the robustness, we analyzed the results in three cases (intra-session, inter-subject, and inter-session) and two movement categories (isometric contraction and dynamic movement). We found that HD-EMG-derived inputs improve the accuracy and robustness of torque prediction of the isometric contractions. However, in dynamic movements, good prediction results could only be achieved by including additional kinematic features (ankle joint position and angular velocity), and the type of EMG input did not strongly influence the results.In the second paper, we investigated the changes in motor unit behavior of the ankle plantar flexor (soleus) and dorsiflexor (tibialis anterior) caused by spinal cord injury (SCI). We computed torque, EMG, and motor unit parameters during volitional sub-maximal voluntary contractions for the SCI group and compared them to a non-injured control cohort. We found that participants in both groups could maintain the prescribed torque with similar variability. However, the SCI group required higher muscle activation levels (normalized to maximum) to achieve the same level of relative torque compared to the control group. The SCI group had lower intramuscular coherence in the alpha frequency band than the control group, indicating altered neural synchronization at the sub-cortical level. The soleus motor unit firing patterns were more variable post-SCI than in the control group. In addition, at high torque levels (50% of personal maximum), both muscle's motor units were recruited and de-recruited at lower torques, and motor units fired at lower rates in the tibialis anterior muscle in persons with SCI, indicating altered force gradation strategies after the injury.The studies presented in this thesis demonstrated that HD-EMG is suitable for robust isometric ankle joint torque prediction, which has potential in applications such as robot-assisted rehabilitation and robotic gait assistive technology. In particular, the robustness and accuracy of HD-EMG-based predictions are essential for improved estimation of the joint torque that can then be used in the human-in-the-loop control scheme. In addition, HD-EMG decomposition enables a non-invasive way to observe the motor unit behavior in vivo in persons with neuromusculoskeletal disorders, which can enhance the understanding of the underlying neurophysiological mechanisms of motor impairments. The insights provided by such HD-EMG analysis in the future may be beneficial for developing targeted interventions and personalized therapies.
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| 11. |
- Kizyte, Asta, 1993-, et al.
(författare)
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Neuromuscular adaptations in ankle plantar flexor and dorsiflexor in persons with spinal cord injury
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Objective: Spinal cord injury (SCI) could lead to sensory-motor impairment of varying degree. After the injury, multiple neurophysiological changes occur, altering the neural motor control strategies. This study aims to assess the neuromuscular adaptations in the ankle plantar flexor and dorsiflexor muscles after the SCI by examining the electromyography (EMG) and motor unit parameters during sub-maximal voluntary isometric contractions and comparing these parameters to a control cohort. Methods: High-density EMG (HD-EMG) signals of tibialis anterior and soleus were recorded simultaneously with ankle joint torque during repeated sub-maximal (20% and 50% of the maximal torque) isometric voluntary contractions. Torque parameters such as normalized torque and coefficient of variation of torque during sustained contraction, EMG parameters such as amplitude and intramuscular coherence, as well as motor unit parameters such as motor unit discharge rates, recruitment thresholds, and coefficient of variation of the inter-spike intervals, were analyzed within the SCI and control groups. Results: We found that the SCI group, on average, had significantly weaker plantar flexor but not dorsiflexor muscles than the control group. Despite the increased variation of soleus motor unit inter-spike intervals post-SCI, both groups maintained constant sub-maximal torques with similar variability. However, the SCI group required up to 40.2% higher normalized EMG amplitudes to achieve the same torque level as the control group. Additionally, intramuscular coherence was found to be lower (up to 38.1% in TA and 34.6% in SOL) in the SCI group compared to the control group in the alpha frequency band during sustained sub-maximal isometric contractions. At higher force levels (50% MVC), motor units were recruited and de-recruited at lower thresholds in both muscles and fired at lower rates in the tibialis anterior muscle post-SCI. Conclusion: Through the analysis of these parameters, we observed altered force production and modulation strategies post-SCI. The observed combination of the motor unit and EMG parameter changes may indicate reduced common neural drive within the muscle and a possible shift towards larger motor units and in both TA and SOL muscles. Significance: The results of this study contribute to the knowledge of the neurophysiological modifications in the ankle dorsiflexors and plantar flexors following the SCI, which may aid future research on SCI rehabilitation.
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| 12. |
- Krishnan, Rakesh, et al.
(författare)
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Reliably Segmenting Motion Reversals of a Rigid-IMU Cluster Using Screw-Based Invariants
- 2018
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Ingår i: 2018 IEEE-RAS 18TH INTERNATIONAL CONFERENCE ON HUMANOID ROBOTS (HUMANOIDS). ; , s. 88-95
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Konferensbidrag (refereegranskat)abstract
- Human-robot interaction (HRI) is moving towards the human-robot synchronization challenge. In robots like exoskeletons, this challenge translates to the reliable motion segmentation problem using wearable devices. Therefore, our paper explores the possibility of segmenting the motion reversals of a rigid-IMU cluster using screw-based invariants. Moreover, we evaluate the reliability of this framework with regard to the sensor placement, speed and type of motion. Overall, our results show that the screw-based invariants can reliably segment the motion reversals of a rigid-IMU cluster.
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| 13. |
- Lidbeck, Cecilia M., et al.
(författare)
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Postural Orientation During Standing in Children With Bilateral Cerebral Palsy
- 2014
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Ingår i: Pediatric Physical Therapy. - 0898-5669 .- 1538-005X. ; 26:2, s. 223-229
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To investigate postural orientation and maintenance of joint position during standing in children with bilateral spastic cerebral palsy (BSCP). Methods: Standing was examined with 3-D motion analysis in 26 children with BSCP, and 19 children typically developing (TD). Two groups of children with cerebral palsy (CP) were analyzed: 15 who were able to maintain standing without support and 11 who needed support. Results: Children with CP stood with more flexion than children TD. In the CP groups, children standing without support stood more asymmetrically with less hip and knee flexion and less movement than those who required support. Conclusion: Children with CP had varying abilities to stand and maintain standing posture with or without support. Both CP groups stood with more flexion than their potential passive joint angle, more obvious in children requiring support. Investigations on how muscle strength and spatial perception influence posture remains to be explored.
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| 14. |
- Liu, Yixing, et al.
(författare)
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A method of detecting human movement intentions in real environments
- 2023
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Ingår i: 2023 international conference on rehabilitation robotics, ICORR. - : Institute of Electrical and Electronics Engineers (IEEE).
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Konferensbidrag (refereegranskat)abstract
- Accurate and timely movement intention detection can facilitate exoskeleton control during transitions between different locomotion modes. Detecting movement intentions in real environments remains a challenge due to unavoidable environmental uncertainties. False movement intention detection may also induce risks of falling and general danger for exoskeleton users. To this end, in this study, we developed a method for detecting human movement intentions in real environments. The proposed method is capable of online self-correcting by implementing a decision fusion layer. Gaze data from an eye tracker and inertial measurement unit (IMU) signals were fused at the feature extraction level and used to predict movement intentions using 2 different methods. Images from the scene camera embedded on the eye tracker were used to identify terrains using a convolutional neural network. The decision fusion was made based on the predicted movement intentions and identified terrains. Four able-bodied participants wearing the eye tracker and 7 IMU sensors took part in the experiments to complete the tasks of level ground walking, ramp ascending, ramp descending, stairs ascending, and stair descending. The recorded experimental data were used to test the feasibility of the proposed method. An overall accuracy of 93.4% was achieved when both feature fusion and decision fusion were used. Fusing gaze data with IMU signals improved the prediction accuracy.
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| 15. |
- Liu, Yixing, et al.
(författare)
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A Muscle Synergy-Inspired Method of Detecting Human Movement Intentions Based on Wearable Sensor Fusion
- 2021
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Ingår i: IEEE transactions on neural systems and rehabilitation engineering. - : Institute of Electrical and Electronics Engineers (IEEE). - 1534-4320 .- 1558-0210. ; 29, s. 1089-1098
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Tidskriftsartikel (refereegranskat)abstract
- Detecting human movement intentions is fundamental to neural control of robotic exoskeletons, as it is essential for achieving seamless transitions between different locomotion modes. In this study, we enhanced a muscle synergy-inspired method of locomotion mode identification by fusing the electromyography data with two types of data from wearable sensors (inertial measurement units), namely linear acceleration and angular velocity. From the finite state machine perspective, the enhanced method was used to systematically identify 2 static modes, 7 dynamic modes, and 27 transitions among them. In addition to the five broadly studied modes (level ground walking, ramps ascent/descent, stairs ascent/descent), we identified the transition between different walking speeds and modes of ramp walking at different inclination angles. Seven combinations of sensor fusion were conducted, on experimental data from 8 able-bodied adult subjects, and their classification accuracy and prediction time were compared. Prediction based on a fusion of electromyography and gyroscope (angular velocity) data predicted transitions earlier and with higher accuracy. All transitions and modes were identified with a total average classification accuracy of 94.5% with fused sensor data. For nearly all transitions, we were able to predict the next locomotion mode 300-500ms prior to the step into that mode.
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| 16. |
- Liu, Yixing, et al.
(författare)
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Joint Kinematics, Kinetics and Muscle Synergy Patterns During Transitions Between Locomotion Modes
- 2023
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Ingår i: IEEE Transactions on Biomedical Engineering. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9294 .- 1558-2531. ; 70:3, s. 1062-1071
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Tidskriftsartikel (refereegranskat)abstract
- There is an increasing demand for accurately predicting human movement intentions. To be effective, predictions must be performed as early as possible in the preceding step, though precisely how early has been studied relatively little; how and when a person's movement patterns in a transition step deviate from those in the preceding step must be clearly defined. In this study, we collected motion kinematics, kinetics and electromyography data from 9 able-bodied participants during 7 locomotion modes. Twelve types of steps between the 7 locomotion modes were studied, including 5 continuous steps (taking another step in the same locomotion mode) and 7 transitions steps (taking a step from one locomotion mode into another). For each joint degree of freedom, joint angles, angular velocities, moments, and moment rates were compared between continuous steps and transition steps, and the relative timing during the transition step at which these parameters diverged from those of a continuous step, which we refer to as transition starting times, were identified using multiple analyses of variance. Muscle synergies were also extracted for each step, and we studied in which locomotion modes these synergies were common (task-shared) and in which modes they were specific (task-specific). The transition starting times varied among different transitions and joint degrees of freedom. Most transitions started in the swing phase of the transition step. These findings can be applied to determine the critical timing at which a powered assistive device must adapt its control to enable safe and comfortable support to a user.
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| 17. |
- Liu, Yixing, et al.
(författare)
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Weight Distribution of a Knee Exoskeleton Influences Muscle Activities During Movements
- 2021
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Ingår i: IEEE Access. - : Institute of Electrical and Electronics Engineers (IEEE). - 2169-3536. ; 9, s. 91614-91624
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Tidskriftsartikel (refereegranskat)abstract
- Lower extremity powered exoskeletons help people with movement disorders to perform daily activities and are used increasingly in gait retraining and rehabilitation. Studies of powered exoskeletons often focus on technological aspects such as actuators, control methods, energy and effects on gait. Limited research has been conducted on how different mechanical design parameters can affect the user. In this paper, we study the effects of weight distributions of knee exoskeleton components on simulated muscle activities during three functional movements. Four knee exoskeleton CAD models were developed based on actual motor and gear reducer products. Different placements of the motor and gearbox resulted in different weight distributions. One unilateral knee exoskeleton prototype was fabricated and tested on 5 healthy subjects. Simulation results were compared to observed electromyography signals. Muscle activities varied among weight distributions and movements, wherein no one physical design was optimal for all movements. We describe how a powered exoskeleton's core components can be expected to affect a user's ability and performance. Exoskeleton physical design should ideally take the user's activity goals and ability into consideration.
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| 18. |
- Liu, Yi-Xing, 1993-, et al.
(författare)
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Joint kinematics, kinetics and muscle synergy patterns during transitions between locomotion modes
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- There is an increasing demand for accurately predicting a person's movement intentions, for instance, for robotic exoskeletons to achieve seamless transitions between locomotion modes. To this end, many methods have been reported to identify locomotion modes and the transitions between them with high classification accuracy. To be effective, predictions must be performed as early as possible in the preceding step, though precisely how early has been studied relatively little; how and when a persons' movement patterns in a transition step deviate from those in the preceding step must be clearly defined. In this study, we collected motion kinematics, kinetics and electromyography data from 9 able-bodied subjects during 7 locomotion modes and transitions between them, and computed joint angles and moments in the hip in frontal and sagittal planes and at the knee and ankle in the sagittal plane. Locomotion modes included level ground walking, ramp and stair ascent and descent, stepping over an obstacle and standing still. Twelve types of steps between the 7 locomotion modes were studied, including 5 continuous steps (taking another step in the same locomotion mode) and 7 transitions (taking a step from one locomotion mode into another). For each joint degree of freedom, four dependent time-series variables, namely joint angles, angular velocities, joint moments, and joint moment rates, as functions of percent gait cycle, were compared between continuous steps and transition steps, and the relative timing during the transition step at which these parameters diverged from those of a continuous step, which we refer to as transition starting time, were identified using multiple analyses of variance. We also compared these parameters during each transition to those in a continuous step in the mode after the transition, to determine whether there are period in the transition step during which kinematics and kinetics are unique. Muscle synergies were also extracted for each continuous and transition step, and we studied in which locomotion modes these synergies were common (task-shared) and in which modes they were specific (task-specific). The transition starting times varied among different transitions and joint degrees of freedom. Most transitions, such as from walking to standing still and from walking to ramp ascent, started in the swing phase of the transition step, though the transition from walking to stepping over an obstacle began earlier, i.e. during mid- to late stance phase. We identified 3-4 task-shared muscle synergies and 1-2 task-specific muscle synergies between each pair of transitions. These findings can be applicability in determining the critical timing at which a powered assistive device must adapt its control to enable safe and comfortable support to a user.
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| 19. |
- Liu, Yi-Xing, et al.
(författare)
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Muscle synergies enable accurate joint moment prediction using few electromyography sensors
- 2021
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Ingår i: 2021 IEEE International Conference on Intelligent Robots and Systems (IROS). - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 5090-5097
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Konferensbidrag (refereegranskat)abstract
- There is an increasing demand for accurate prediction of joint moments using wearable sensors for robotic exoskeletons to achieve precise control and for rehabilitation care to remotely monitor users’ condition. In this study, we used electromyography (EMG) signals to first identify muscle synergies, then used them to train of a long short-term memory network to predict knee joint moments during walking. Kinematics, ground reaction forces, and EMG from 10 muscles on the right limb were collected from 6 able-bodied subjects during normal gait. Between 4 and 6 muscle synergies were extracted from the EMG signals, generating two outputs - the muscle synergies weight matrix and the time-dependent muscle synergies action signals. The muscle synergies action signals and measured knee joint moments from inverse dynamics were then used as inputs to train the joint moment prediction model using a long short-term memory network. For testing, between4 and 7 EMG signals were used to estimate the muscle synergies action signals with the extracted muscle synergies weights matrix. The estimated muscle synergies action signals were then used to predict knee joint moments. Knee joint moments were also predicted directly from all 10 EMGs, then from 4-7EMG signals using another long short-term memory network. Prediction accuracy from the synergies-trained network vs. the EMG-trained network were compared, using the same number of EMG signals in each. Prediction error with respect to moments measured via inverse dynamics was computed for both networks. Knee moments predicted with as few as 4 EMGswas at least as accurate as moments predicted from all 10 EMGswhen muscle synergies were exploited. Predicted knee moments from muscle synergies achieved an average of 4.63% root mean square error from 4 EMG signals, which was lower than error when predicted directly from 4 EMG signals (5.63%).
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| 20. |
- Luis, Israel, et al.
(författare)
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Evaluation of musculoskeletal models, scaling methods, and performance criteria for estimating muscle excitations and fiber lengths across walking speeds
- 2022
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Ingår i: Frontiers in Bioengineering and Biotechnology. - : Frontiers Media SA. - 2296-4185. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Muscle-driven simulations have been widely adopted to study muscle-tendon behavior; several generic musculoskeletal models have been developed, and their biofidelity improved based on available experimental data and computational feasibility. It is, however, not clear which, if any, of these models accurately estimate muscle-tendon dynamics over a range of walking speeds. In addition, the interaction between model selection, performance criteria to solve muscle redundancy, and approaches for scaling muscle-tendon properties remain unclear. This study aims to compare estimated muscle excitations and muscle fiber lengths, qualitatively and quantitatively, from several model combinations to experimental observations. We tested three generic models proposed by Hamner et al., Rajagopal et al., and Lai-Arnold et al. in combination with performance criteria based on minimization of muscle effort to the power of 2, 3, 5, and 10, and four approaches to scale the muscle-tendon unit properties of maximum isometric force, optimal fiber length, and tendon slack length. We collected motion analysis and electromyography data in eight able-bodied subjects walking at seven speeds and compared agreement between estimated/modelled muscle excitations and observed muscle excitations from electromyography and computed normalized fiber lengths to values reported in the literature. We found that best agreement in on/off timing in vastus lateralis, vastus medialis, tibialis anterior, gastrocnemius lateralis, gastrocnemius medialis, and soleus was estimated with minimum squared muscle effort than to higher exponents, regardless of model and scaling approach. Also, minimum squared or cubed muscle effort with only a subset of muscle-tendon unit scaling approaches produced the best time-series agreement and best estimates of the increment of muscle excitation magnitude across walking speeds. There were discrepancies in estimated fiber lengths and muscle excitations among the models, with the largest discrepancy in the Hamner et al. model. The model proposed by Lai-Arnold et al. best estimated muscle excitation estimates overall, but failed to estimate realistic muscle fiber lengths, which were better estimated with the model proposed by Rajagopal et al. No single model combination estimated the most accurate muscle excitations for all muscles; commonly observed disagreements include onset delay, underestimated co-activation, and failure to estimate muscle excitation increments across walking speeds.
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| 21. |
- Luis, Israel, et al.
(författare)
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Experiment-guided tuning of muscle fiber lengths and passive forces
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Musculoskeletal simulations can provide insights into the roles of muscles and tendons during motion. Accuratedescriptions of musculoskeletal parameters increase our confidence in the estimations of dynamics andenergetics of muscles, tendons, and joints. In this study, we present a computational tool to tune muscle-tendonparameters based on prior experimental observations in literature and evaluate their influence on estimatedmuscle excitations. From a scaled generic musculoskeletal model, we tuned optimal fiber length, tendon slacklength, and tendon stiffness to match reported digitalized images from ultrasound, and muscle passive curvesto match reported in vivo experimental angle-moment relationship. Our proposed workflow improved theestimation of muscle fiber lengths in the ankle plantarflexors compared to linearly scaling optimal fiber lengthsand tendon slack lengths. Also, with tuned muscle-tendon parameters, estimated the on/off timing of nearly allmuscles’ excitations in the model compared to reported values in literature. Our workflow customizes muscletendonparameters easily and quickly. The computational toolbox is freely available online.Keywords
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| 22. |
- Luis, Israel, et al.
(författare)
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Experiment-guided tuning of muscle–tendon parameters to estimate muscle fiber lengths and passive forces
- 2024
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- The workflow to simulate motion with recorded data usually starts with selecting a generic musculoskeletal model and scaling it to represent subject-specific characteristics. Simulating muscle dynamics with muscle–tendon parameters computed from existing scaling methods in literature, however, yields some inconsistencies compared to measurable outcomes. For instance, simulating fiber lengths and muscle excitations during walking with linearly scaled parameters does not resemble established patterns in the literature. This study presents a tool that leverages reported in vivo experimental observations to tune muscle–tendon parameters and evaluates their influence in estimating muscle excitations and metabolic costs during walking. From a scaled generic musculoskeletal model, we tuned optimal fiber length, tendon slack length, and tendon stiffness to match reported fiber lengths from ultrasound imaging and muscle passive force–length relationships to match reported in vivo joint moment–angle relationships. With tuned parameters, muscle contracted more isometrically, and soleus’s operating range was better estimated than with linearly scaled parameters. Also, with tuned parameters, on/off timing of nearly all muscles’ excitations in the model agreed with reported electromyographic signals, and metabolic rate trajectories varied significantly throughout the gait cycle compared to linearly scaled parameters. Our tool, freely available online, can customize muscle–tendon parameters easily and be adapted to incorporate more experimental data.
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| 23. |
- Luis, Israel, et al.
(författare)
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Insights into muscle metabolic energetics: Modelling muscle-tendon mechanics and metabolicrates during walking across speeds
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The metabolic energy rate of individual muscles is impossible to measure without invasive procedures. Priorstudies have produced models to predict metabolic rates based on experimental observations of isolated musclecontraction from various species. Such models can provide reliable predictions of metabolic rates in humans ifmuscle properties and control are accurately modelled. This study aimed to examine how muscle-tendon modelcalibration and metabolic energy models influenced estimation of muscle-tendon states and time-seriesmetabolic rates, to evaluate the agreement with empirical data, and to provide predictions of the metabolic rateof muscle groups and gait phases across walking speeds. Three-dimensional musculoskeletal simulations withprescribed kinematics and dynamics were performed. An optimal control formulation was used to computemuscle-tendon states with four levels of individualization, ranging from a scaled generic model and musclecontrols based on minimal activations, to calibration of passive muscle forces, personalization of Achilles andquadriceps tendon stiffnesses, to finally informing muscle controls with electromyography. We computedmetabolic rates based on existing models. Simulations with calibrated passive forces and personalized tendonstiffness most accurately estimate muscle excitations and fiber lengths. Interestingly, the inclusion ofelectromyography did not improve our estimates. The whole-body average metabolic cost was better estimatedusing Bhargava et al. 2004 and Umberger 2010 models. We estimated metabolic rate peaks near early stance,pre-swing, and initial swing at all walking speeds. Plantarflexors accounted for the highest cost among musclegroups at the preferred speed and was similar to the cost of hip adductors and abductors combined. Also, theswing phase accounted for slightly more than one-quarter of the total cost in a gait cycle, and its relative costdecreased with walking speed. Our prediction might inform the design of assistive devices and rehabilitationtreatment. The code and experimental data are available online.
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| 24. |
- Luis, Israel, et al.
(författare)
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Springs vs. motors: Ideal assistance in the lower limbs during walking at different speeds
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Recent years have witnessed break throughs in assistive exoskeletons; both passive and active devices have reduced metabolic costs near preferred walking speed by assisting muscle actions. Metabolic reductions at multiple speeds should thus also be attainable. Musculo skeletal simulation can potentially predict the interaction between assistive moments, muscle-tendon mechanics, and walking energetics. In this study, we simulated devices’ optimal assistive moments based on minimal muscle activations during walking with prescribed kinematics and dynamics. We used a generic musculo skeletal model with calibrated muscle-tendon parameters and computed metabolic rates from muscle actions. We then simulated walking across multiple speeds and with two ideal actuation modes – motor-based and spring-based – to assist ankle plantar flexion,knee extension, hip flexion, and hip abduction and compared computed metabolic rates. We found that both actuation modes considerably reduced physiological joint moments but did not always reduce metabolic rates. Compared to unassisted conditions, motor-based ankle plantar flexion and hip flexion assistance reduced metabolic rates, and this effect was more pronounced as walking speed increased. Spring-based hip flexion and abduction assistance increased metabolic rates at some walking speeds despite a moderate decrease in some muscle activations. Both modes of knee extension assistance reduced metabolic rates to a small extent, eventhough the actuation contributed with practically the entire net knee extension moment during stance. Motorbased hip abduction assistance reduced metabolic rates more than spring-based assistance, though this reduction was relatively small. Future work should experimentally validate the effects of assistive moments andrefine modeling assumptions accordingly. Our computational workflow is freely available online.
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| 25. |
- Luis, Israel
(författare)
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Walking efficiently with smart springs
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Numerous assistive exoskeletons have been developed in recent years to assist walking in individuals with and without motor disorders. A standard metric to measure the efficacy of assistance is the change in the metabolic energy cost between unassisted and assisted conditions. Various experimental methods, such as human-in-the-loop optimization, have been developed to find the optimal exoskeleton control to minimize metabolic energy. Such an approach is powerful yet time- and resource-intensive. In this regard, computational methods might complement state-of-the-art experimental approaches. Developing accurate models of the musculoskeletal system and neuromuscular commands could accelerate the development of exoskeletons and improve our understanding of human-exoskeleton interaction. The aims of the thesis were to model and simulate muscle-tendon mechanics and energetics of walking across speeds in unassisted conditions and with the support of ideal exoskeleton assistance with two modes of assistance: motor-based and spring-based actuators. The first three studies examined multiple musculoskeletal models, calibration methods of the muscle-tendon architecture, performance criteria for solving the muscle redundancy, and metabolic energy models to accurately estimate muscle excitations, fiber lengths, and metabolic energy cost compared to available experimental data. The musculoskeletal model proposed by Rajagopal et al. with calibrated muscle passive fiber-length curves and personalized Achilles and patellar tendon stiffness provided good agreement with muscle excitations and fiber lengths obtained from electromyographic signal and ultrasound imaging, respectively. Also, among multiple metabolic energy models in the literature, the model proposed by Bhargava et al. best estimated the average metabolic rates of the whole body compared to experimental measurements computed from spiroergometry. With the best estimations of muscle-tendon mechanics and energetics, the relative cost of the stance phase was predicted to increase significantly with walking speeds, and the metabolic cost of ankle plantarflexors was the highest among muscle groups and increased with walking speeds. The fourth study examined the optimal assistance to reduce muscle activations using motor-based and spring-based assistance of ankle plantarflexor, knee extensor, hip flexor, and hip abductor muscle groups. The largest reduction of muscle activation compared to unassisted conditions was obtained with hip flexor assistance with both actuation systems at high walking speeds. The reduction of metabolic rates compared to unassisted conditions was greater with walking speed with motor-based ankle plantarflexor assistance. In contrast, assisting this muscle group with spring-based actuation resulted in lower metabolic cost compared to unassisted conditions as walking speed increased. Interestingly, the decrease in muscle activations did not necessarily imply a reduction of metabolic energy cost compared to unassisted conditions, for instance with spring-based hip flexor and abductor assistance at some walking speeds. Metabolic energy rates during specific periods of the gait cycle were larger than in unassisted conditions due to increased muscle positive work, which is associated with high metabolic cost. The computational methods in the thesis might inspire future studies in the field. The software to calibrate muscle-tendon parameters, such as tendon compliance based on electromyography and muscle passive force-length curves based on ultrasound imaging, and to simulate exoskeleton assistance, are available in public repositories and can be adapted to integrate more experimental observations and simulate other motions than walking. Future studies will validate the predicted muscle-tendon mechanics with exoskeleton assistance.
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| 26. |
- Rakesh, Krishnan, et al.
(författare)
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A survey of human shoulder functional kinematic representations
- 2019
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Ingår i: Medical and Biological Engineering and Computing. - Heidelberg : SPRINGER HEIDELBERG. - 0140-0118 .- 1741-0444. ; 57:2, s. 339-367
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Forskningsöversikt (refereegranskat)abstract
- In this survey, we review the field of human shoulder functional kinematic representations. The central question of this review is to evaluate whether the current approaches in shoulder kinematics can meet the high-reliability computational challenge. This challenge is posed by applications such as robot-assisted rehabilitation. Currently, the role of kinematic representations in such applications has been mostly overlooked. Therefore, we have systematically searched and summarised the existing literature on shoulder kinematics. The shoulder is an important functional joint, and its large range of motion (ROM) poses several mathematical and practical challenges. Frequently, in kinematic analysis, the role of the shoulder articulation is approximated to a ball-and-socket joint. Following the high-reliability computational challenge, our review challenges this inappropriate use of reductionism. Therefore, we propose that this challenge could be met by kinematic representations, that are redundant, that use an active interpretation and that emphasise on functional understanding.
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| 27. |
- Riad, Jacques, et al.
(författare)
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Are Muscle Volume Differences Related to Concentric Muscle Work During Walking in Spastic Hemiplegic Cerebral Palsy?
- 2012
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Ingår i: Clinical Orthopaedics and Related Research. - : Ovid Technologies (Wolters Kluwer Health). - 0009-921X .- 1528-1132. ; 470:5, s. 1278-1285
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Tidskriftsartikel (refereegranskat)abstract
- Background: Individuals with spastic hemiplegic cerebral palsy are typically high functioning and walk without assistive devices. The involved limb is usually smaller and shorter, although it is not clear whether the difference in muscle volume has an impact on walking capacity. Questions/purposes: We determined the volume of muscles important for propulsion and related that volume to concentric muscle work during walking on the hemiplegic and noninvolved sides in patients with cerebral palsy. Patients and Methods: We studied 46 patients (mean age, 17.6 years; range, 13-24 years) with spastic hemiplegic cerebral palsy. We assessed muscle volume using MRI and concentric muscle work in the sagittal plane from the hip, knee, and ankle using three-dimensional gait analysis. Patients were classified by Winters' criteria to assess the involvement of cerebral palsy and movement pattern during walking. Results: On the hemiplegic side, muscles were smaller, except for the gracilis muscle, and concentric muscle work from the ankle plantar flexors, knee extensors, and hip flexors and extensors was lower compared to the noninvolved side. Hip extensor work was higher on the hemiplegic and the noninvolved sides compared to a control group of 14 subjects without cerebral palsy. Hemiplegic to noninvolved volume ratios correlated with work ratios (r = 0.40-0.66). The Winters classification and previous calf muscle surgery predicted work ratios. Conclusions: Our observations of smaller muscles on the hemiplegic side and changes in muscle work on both sides can help us distinguish between primary deviations that may potentially be treatable and compensatory mechanisms that should not be treated.
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| 28. |
- Romanato, M., et al.
(författare)
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Influence of different calibration methods on surface electromyography-informed musculoskeletal models with few input signals
- 2023
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Ingår i: Clinical Biomechanics. - : Elsevier BV. - 0268-0033 .- 1879-1271. ; 109
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Tidskriftsartikel (refereegranskat)abstract
- Background: Although model personalization is critical when assessing individuals with morphological or neurological abnormalities, or even non-disabled subjects, its translation into routine clinical settings is hampered by the cumbersomeness of experimental data acquisition and lack of resources, which are linked to high costs and long processing pipelines. Quantifying the impact of neglecting subject-specific information in simulations that aim to estimate muscle forces with surface electromyography informed modeling approaches, can address their potential in relevant clinical questions. The present study investigates how different methods to fine-tune subject-specific neuromuscular parameters, reducing the number of electromyography input data, could affect the estimation of the unmeasured excitations and the musculotendon forces. Methods: Three-dimensional motion analysis was performed on 8 non-disabled adult subjects and 13 electromyographic signals captured. Four neuromusculoskeletal models were created for 8 participants: a reference model driven by a large set of sEMG signals; two models informed by four electromyographic signals but calibrated in different fashions; a model based on static optimization. Findings: The electromyography-informed models better predicted experimental excitations, including the unmeasured ones. The model based on static optimization obtained less reliable predictions of the experimental data. When comparing the different reduced models, no major differences were observed, suggesting that the less complex model may suffice for predicting muscle forces with a small set of input in clinical gait analysis tasks. Interpretation: Quantitative model performance evaluation in different conditions provides an objective indication of which method yields the most accurate prediction when a small set of electromyographic recordings is available.
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| 29. |
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| 30. |
- Sandamas, Paul, et al.
(författare)
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The effect of a reduced first step width on starting block and first stance power and impulses during an athletic sprint start.
- 2019
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Ingår i: Journal of Sports Sciences. - : Taylor & Francis. - 0264-0414 .- 1466-447X. ; 37:9, s. 1046-1054
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Tidskriftsartikel (refereegranskat)abstract
- This study investigated how manipulating first step width affects 3D external force production, centre of mass (CoM) motion and performance in athletic sprinting. Eight male and 2 female competitive sprinters (100m PB: 11.03 ± 0.36 s male and 11.6 ± 0.45 s female) performed 10 maximal effort block starts. External force and three-dimensional kinematics were recorded in both the block and first stance phases. Five trials were performed with the athletes performing their preferred technique (Skating) and five trials with the athletes running inside a 0.3 m lane (Narrow). By reducing step width from a mean of 0.31 ± 0.06 m (Skating) to 0.19 ± 0.03 m (Narrow), reductions were found between the two styles in medial block and medial 1st stance impulses, 1st stance anterior toe-off velocity and mediolateral motion of the CoM. No differences were found in block time, step length, stance time, average net resultant force vector, net anteroposterior impulse nor normalised external power. Step width correlated positively with medial impulse but not with braking nor net anteroposterior impulse. Despite less medially directed forces and less mediolateral motion of the CoM in the Narrow trials, no immediate improvement to performance was found by restricting step width.
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| 31. |
- Sandamas, Paul, et al.
(författare)
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The relationships between pelvic range of motion, step width and performance during an athletic sprint start
- 2020
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Ingår i: Journal of Sports Sciences. - : Routledge. - 0264-0414 .- 1466-447X. ; 38:19, s. 2200-2207
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Tidskriftsartikel (refereegranskat)abstract
- The aims of this study were (a) to describe the kinematics underlying the phenomenon of the knee of the swing leg passing medially in front of the athlete during the single push (SP) phase of the block sprint start, and (b) to determine the relationships between block phase pelvis range of motion (RoM), 1st step width and block phase performance. Three-dimensional kinematic data (250 Hz) were collected from eleven competitive sprinters (100 m PB: 11.17 ± 0.41) performing maximal effort block starts. The joint angles of the rear hip with respect to the pelvis and the pelvis segment angles with respect to the laboratory coordinate system were calculated during the block start phase to the end of the 1st stance. A combination of pelvis list and rotation (not hip adduction) was coupled with the thigh of the swing leg moving medially during the SP phase. A very high positive correlation was found between pelvic list RoM and 1st step width (r = 0.799, p = 0.003). No other significant correlations were found. Attempting to reduce pelvic RoM or changing frontal and transverse plane hip joint angles to minimise medial thigh motion is unlikely to lead to an improvement to performance.
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| 32. |
- Sjöberg, Maria
(författare)
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Biomechanical analyses of flywheel resistance exercise : From a space- and ground-based perspective
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Astronauts suffer degradation of postural muscles and weight-bearing bones during long-duration spaceflight. Resistance exercise is used as a primary countermeasure against these degradations. However, it has proven difficult to predict appropriate exercise loads, and the countermeasure regimens in current use are not fully preventing bone and muscle loss. It is likely that gravity-independent exercise devices, based on flywheel inertial resistance, will be implemented in future musculoskeletal countermeasure regimens.In this thesis, biomechanical analyses of external and internal exercise loads during flywheel leg resistance exercises, were performed through experimental data collection and musculoskeletal modelling. The thesis is based on four separate studies with the collective aim to provide knowledge that can be implemented when designing flywheel-based strength-training regimens to be used both in terrestrial settings and as countermeasures against musculoskeletal deconditioning in weightlessness.The first study analyzed computed joint kinematics and kinetics, and relative muscle forces in the lower limb during maximal effort flywheel leg press (FWLP) and flywheel squat (FWS) exercises. Results showed that total exercise load was slightly higher during FWS than FWLP, whereas relative muscle force did not differ between the two exercises, suggesting that they may have similar strength training effects.The second study investigated the effect of gravity on internal joint load distribution during leg resistance exercise. This was done in two steps: 1) by comparing joint kinetics during FWLP and FWS at a given submaximal exercise load (80% of the isometric maximum load in FWLP), and 2) by simulating both FWLP and FWS in zero gravity and studying changes in joint loads. The first step revealed greater hip extension moment and lumbar joint-contact forces in FWLP than in FWS, indicating a notable effect of the direction of motion relative to the gravity vector, on body load distribution. Step two showed similar, or lower, joint loads in FWLP when gravity was removed, whereas in FWS, removal of gravity resulted in increased hip extension moment and lumbar force. Collectively, the results suggest that FWLP is a better ground-based analogue than FWS for leg-resistance exercise in space.The third study examined the accuracy of a pressure insole system regarding measurements of centre of pressure and ground reaction force during resistance exercises. The results showed that insoles are capable of accurately measuring centre of pressure at loads higher than 250 N and that force measurements are accurate in exercises involving mainly vertical ground reaction forces, but appears to overestimate ground reaction force for exercises involving greater portions of shear force.The fourth study analyzed low-back loads during FWLP, FWS and barbell back squat. Lumbar compression forces were high and similar in the three exercises, suggesting that the flywheel exercises are capable of stimulating vertebral bone regeneration without inflicting risk of vertebral fractures. Muscle engagement in the investigated back extensors were lower in FWLP than in the other two exercises, although presumed high enough to counteract space-induced atrophy if implemented in countermeasure training regimens.
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| 33. |
- Sjöberg, Maria, et al.
(författare)
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Comparison of Joint and Muscle Biomechanics in Maximal Flywheel Squat and Leg Press
- 2021
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Ingår i: Frontiers in Sports and Active Living. - : Frontiers Media SA. - 2624-9367. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- The aim was to compare the musculoskeletal load distribution and muscle activity in two types of maximal flywheel leg-extension resistance exercises: horizontal leg press, during which the entire load is external, and squat, during which part of the load comprises the body weight. Nine healthy adult habitually strength-training individuals were investigated. Motion analysis and inverse dynamics-based musculoskeletal modelling were used to compute joint loads, muscle forces, and muscle activities. Total exercise load (resultant ground reaction force; rGRF) and the knee-extension net joint moment (NJM) were slightly and considerably greater, respectively, in squat than in leg press (p <= 0.04), whereas the hip-extension NJM was moderately greater in leg press than in squat (p = 0.03). Leg press was performed at 11 degrees deeper knee-flexion angle than squat (p = 0.01). Quadriceps muscle activity was similar in squat and leg press. Both exercise modalities showed slightly to moderately greater force in the vastii muscles during the eccentric than concentric phase of a repetition (p <= 0.05), indicating eccentric overload. That the quadriceps muscle activity was similar in squat and leg press, while rGRF and NJM about the knee were greater in squat than leg press, may, together with the finding of a propensity to perform leg press at deeper knee angle than squat, suggest that leg press is the preferable leg-extension resistance exercise, both from a training efficacy and injury risk perspective.
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| 34. |
- Sjöberg, Maria, et al.
(författare)
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Influence of gravity on biomechanics in flywheel squat and leg press.
- 2023
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Ingår i: Sports Biomechanics. - : Informa UK Limited. - 1476-3141 .- 1752-6116. ; 22:6, s. 767-783
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Tidskriftsartikel (refereegranskat)abstract
- Resistance exercise on Earth commonly involves both body weight and external load. When developing exercise routines and devices for use in space, the absence of body weight is not always adequately considered. This study compared musculoskeletal load distribution during two flywheel resistance knee-extension exercises, performed in the direction of (vertical squat; S) or perpendicular to (horizontal leg press; LP) the gravity vector. Eleven participants performed these two exercises at a given submaximal load. Motion analysis and musculoskeletal modelling were used to compute joint loads and to simulate a weightless situation. The flywheel load was more than twice as high in LP as in S (p < 0.001). Joint moments and forces were greater during LP than during S in the ankle, hip and lower back (p < 0.01) but were similar in the knee. In the simulated weightless situation, hip and lower-back loadings in S were higher than corresponding values at Earth gravity (p ≤ 0.01), whereas LP joint loads did not increase. The results suggest that LP is a better terrestrial analogue than S for knee-extension exercise in weightlessness and that the magnitude and direction of gravity during resistance exercise should be considered when designing and evaluating countermeasure exercise routines and devices for space.
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| 35. |
- Sjöberg, Maria, et al.
(författare)
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Lumbar Loads and Muscle Activity During Flywheel and Barbell Leg Exercises
- 2023
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Ingår i: Journal of Strength and Conditioning Research. - : Ovid Technologies (Wolters Kluwer Health). - 1064-8011 .- 1533-4287. ; 37:1, s. 27-34
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Tidskriftsartikel (refereegranskat)abstract
- It is anticipated that flywheel-based leg resistance exercise will be implemented in future long-duration space missions, to counter deconditioning of weight-bearing bones and postural muscles. The aim was to examine low back loads and muscle engagements during flywheel leg press (FWLP) and flywheel squat (FWS) and, for comparisons, free-weight barbell back squat (BBS). Eight resistance-trained subjects performed 8 repetition maximums of FWLP, FWS, and BBS. Motion analysis and inverse dynamics-based musculoskeletal modeling were used to compute joint loads and muscle forces. Muscle activities were measured with electromyography (EMG). At the L4–L5 level, peak vertebral compression force was similarly high in all exercise modes, whereas peak vertebral posteroanterior shear force was greater (p < 0.05) in FWLP and BBS than in FWS. Among the back-extensor muscles, the erector spinae longissimus exerted the greatest peak force, with no difference between exercises. Peak force in the lumbar multifidus was lower (p < 0.05) during FWLP than during FWS and BBS. Peak EMG activity in the lumbar extensor muscles ranged between 31 and 122% of maximal voluntary isometric contraction across muscles and exercise modes, with the greatest levels in the lumbar multifidus. The vertebral compression forces and muscle activations during the flywheel exercises were sufficiently high to presume that when implementing such exercise in space countermeasure regimens, they may be capable of preventing muscle atrophy and vertebral demineralization in the lumbar region.
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| 36. |
- Su, Binbin, et al.
(författare)
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Gait Phase Recognition Using Deep Convolutional Neural Network with Inertial Measurement Units
- 2020
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Ingår i: Biosensors. - : MDPI AG. - 2079-6374. ; 10:9, s. 109-109
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Tidskriftsartikel (refereegranskat)abstract
- Gait phase recognition is of great importance in the development of assistance-as-needed robotic devices, such as exoskeletons. In order for a powered exoskeleton with phase-based control to determine and provide proper assistance to the wearer during gait, the user’s current gait phase must first be identified accurately. Gait phase recognition can potentially be achieved through input from wearable sensors. Deep convolutional neural networks (DCNN) is a machine learning approach that is widely used in image recognition. User kinematics, measured from inertial measurement unit(IMU) output, can be considered as an ‘image’ since it exhibits some local ‘spatial’ pattern when the sensor data is arranged in sequence. We propose a specialized DCNN to distinguish five phases in a gait cycle, based on IMU data and classified with foot switch information. The DCNN showed approximately 97% accuracy during an offline evaluation of gait phase recognition. Accuracy was highest in the swing phase and lowest in terminal stance.
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| 37. |
- Su, Binbin, et al.
(författare)
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Gait Trajectory and Gait Phase Prediction Based on an LSTM Network
- 2020
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Ingår i: Sensors. - : MDPI AG. - 1424-8220. ; 20:24, s. 7127-7127
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Tidskriftsartikel (refereegranskat)abstract
- Lower body segment trajectory and gait phase prediction is crucial for the control of assistance-as-needed robotic devices, such as exoskeletons. In order for a powered exoskeleton with phase-based control to determine and provide proper assistance to the wearer during gait, we propose an approach to predict segment trajectories up to 200 ms ahead (angular velocity of the thigh, shank, and foot segments) and five gait phases (loading response, mid-stance, terminal stance, preswing, and swing), based on collected data from inertial measurement units placed on the thighs, shanks, and feet. The approach we propose is a long-short term memory (LSTM)-based network, a modified version of recurrent neural networks, which can learn order dependence in sequence prediction problems. The algorithm proposed has a weighted discount loss function that places more weight in predicting the next three to five time frames but also contributes to an overall prediction performance for up to 10 time frames. The LSTM model was designed to learn lower limb segment trajectories using training samples and was tested for generalization across participants. All predicted trajectories were strongly correlated with the measured trajectories, with correlation coefficients greater than 0.98. The proposed LSTM approach can also accurately predict the five gait phases, particularly the swing phase with 95% accuracy in inter-subject implementation. The ability of the LSTMnetwork to predict future gait trajectories and gait phases can be applied in designing exoskeleton controllers that can better compensate for system delays to smooth the transition between gait phases.
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| 38. |
- Su, Binbin, et al.
(författare)
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Locomotion mode transition prediction based on gait event identification using wearable sensors and multilayer perceptrons
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- People walk on different terrains daily, for instance, level-ground walking, ramp and stair ascent and descent, and stepping over obstacles are common activities in daily life. Movementspatterns change as people move from one terrain to another. Prediction of transitions between locomotion modes is important for developing assistive devices such as exoskeletons, as optimal assistive strategies may differ for different locomotion modes. Prediction of locomotion mode transitions is often accompanied by gait event detection that provides important information during locomotion about critical events, such as foot contact (FC) and toe off (TO). In this study, we introduce a method to integrate locomotion mode prediction and gait event identification into one machine learning framework, comprised of two multilayer perceptrons (MLP). Input features to the framework were from fused data from wearable sensors, specifically, electromyography sensors and inertial measurement units. The first MLP successfully identified FC and TO; FC events were identified accurately, and a small number of misclassifications only occurred near TO events. A small time difference (2.5 ms and -5.3 ms for FC and TO respectively) was found between predicted and true gait events. The second MLP correctly identified walking, ramp ascent, and ramp descent transitions with the best aggregate accuracy of 96.3%, 90.1%, and 90.6%, respectively, with sufficient prediction time prior to the critical events. The models in this study demonstrate high accuracy in predicting transitions between different locomotion modes in the same side’s mid-to late stance of the stride prior to the step into the new model using data from EMG and IMUs sensors. Our results may help assistive devices achieve smooth and seamless transitions in different locomotion modes for the person with motor disorders.
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| 39. |
- Su, Binbin, et al.
(författare)
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Locomotion Mode Transition Prediction Based on Gait-Event Identification Using Wearable Sensors and Multilayer Perceptrons
- 2021
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Ingår i: Sensors. - : MDPI AG. - 1424-8220. ; 21:22, s. 7473-
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Tidskriftsartikel (refereegranskat)abstract
- People walk on different types of terrain daily; for instance, level-ground walking, ramp and stair ascent and descent, and stepping over obstacles are common activities in daily life. Movement patterns change as people move from one terrain to another. The prediction of transitions between locomotion modes is important for developing assistive devices, such as exoskeletons, as the optimal assistive strategies may differ for different locomotion modes. The prediction of locomotion mode transitions is often accompanied by gait-event detection that provides important information during locomotion about critical events, such as foot contact (FC) and toe off (TO). In this study, we introduce a method to integrate locomotion mode prediction and gait-event identification into one machine learning framework, comprised of two multilayer perceptrons (MLP). Input features to the framework were from fused data from wearable sensors-specifically, electromyography sensors and inertial measurement units. The first MLP successfully identified FC and TO, FC events were identified accurately, and a small number of misclassifications only occurred near TO events. A small time difference (2.5 ms and -5.3 ms for FC and TO, respectively) was found between predicted and true gait events. The second MLP correctly identified walking, ramp ascent, and ramp descent transitions with the best aggregate accuracy of 96.3%, 90.1%, and 90.6%, respectively, with sufficient prediction time prior to the critical events. The models in this study demonstrate high accuracy in predicting transitions between different locomotion modes in the same side's mid- to late stance of the stride prior to the step into the new mode using data from EMG and IMU sensors. Our results may help assistive devices achieve smooth and seamless transitions in different locomotion modes for those with motor disorders.
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| 40. |
- Su, Binbin, et al.
(författare)
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Simulating human walking : a model-based reinforcement learning approach with musculoskeletal modeling
- 2023
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Ingår i: Frontiers in Neurorobotics. - : Frontiers Media SA. - 1662-5218. ; 17
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Tidskriftsartikel (refereegranskat)abstract
- IntroductionRecent advancements in reinforcement learning algorithms have accelerated the development of control models with high-dimensional inputs and outputs that can reproduce human movement. However, the produced motion tends to be less human-like if algorithms do not involve a biomechanical human model that accounts for skeletal and muscle-tendon properties and geometry. In this study, we have integrated a reinforcement learning algorithm and a musculoskeletal model including trunk, pelvis, and leg segments to develop control modes that drive the model to walk.MethodsWe simulated human walking first without imposing target walking speed, in which the model was allowed to settle on a stable walking speed itself, which was 1.45 m/s. A range of other speeds were imposed for the simulation based on the previous self-developed walking speed. All simulations were generated by solving the Markov decision process problem with covariance matrix adaptation evolution strategy, without any reference motion data.ResultsSimulated hip and knee kinematics agreed well with those in experimental observations, but ankle kinematics were less well-predicted.DiscussionWe finally demonstrated that our reinforcement learning framework also has the potential to model and predict pathological gait that can result from muscle weakness.
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| 41. |
- Su, Binbin, et al.
(författare)
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Simulating Human Walking: A Model-BasedReinforcement Learning Approach with musculoskeletal Modelling
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Recent advancements in reinforcement learning algorithms have accelerated the development of control models with high-dimensional inputs and outputs that can reproduce human movement. However, the produced motion tends to be less human-like if algorithms do not involve a biomechanical human model that accounts for skeletal and muscle-tendon properties and geometry. In this study, we have integrated a reinforcement learning algorithm and a musculoskeletal model including trunk, pelvis, and leg segments to develop control modes that drive the model to walk. We simulated human walking first without imposing target walking speed, in which the model was allowed to settle on a stable walking speed itself. A range of other speeds were imposed for the simulation based on the previous self-developed walking speed. All simulations were generated by solving the Markov decision process problem with covariance matrix adaptation evolution strategy, without any reference motion data. We finally demonstrated that our reinforcement learning framework also has the potential to model and predict pathological gait that can result from muscle weakness.
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| 42. |
- Truong, Minh, 1994-
(författare)
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Quantifying Gait Characteristics and Neurological Effects in people with Spinal Cord Injury using Data-Driven Techniques
- 2024
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Spinal cord injury, whether traumatic or nontraumatic, can partially or completely damage sensorimotor pathways between the brain and the body, leading to heterogeneous gait abnormalities. Mobility impairments also depend on other factors such as age, weight, time since injury, pain, and walking aids used. The ASIA Impairment Scale is recommended to classify injury severity, but is not designed to characterize individual ambulatory capacity. Other standardized tests based on subjective or timing/distance assessments also have only limited ability to determine an individual's capacity. Data-driven techniques have demonstrated effectiveness in analysing complexity in many domains and may provide additional perspectives on the complexity of gait performance in persons with spinal cord injury. The studies in this thesis aimed to address the complexity of gait and functional abilities after spinal cord injury using data-driven approaches.The aim of the first manuscript was to characterize the heterogeneous gait patterns in persons with incomplete spinal cord injury. Dissimilarities among gait patterns in the study population were quantified with multivariate dynamic time warping. Gait patterns were classified into six distinct clusters using hierarchical agglomerative clustering. Through random forest classifiers with explainable AI, peak ankle plantarflexion during swing was identified as the feature that most often distinguished most clusters from the controls. By combining clinical evaluation with the proposed methods, it was possible to provide comprehensive analyses of the six gait clusters. The aim of the second manuscript was to quantify sensorimotor effects on walking performance in persons with spinal cord injury. The relationships between 11 input features and 2 walking outcome measures - distance walked in 6 minutes and net energy cost of transport - were captured using 2 Gaussian process regression models. Explainable AI revealed the importance of muscle strength on both outcome measures. Use of walking aids also influenced distance walked, and cardiovascular capacity influenced energy cost. Analyses for each person also gave useful insights into individual performance. The findings from these studies demonstrate the large potential of advanced machine learning and explainable AI to address the complexity of gait function in persons with spinal cord injury.
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| 43. |
- Truong, Minh T.N. 1994-, et al.
(författare)
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Estimation of Sensorimotor Effects on Walking Performance in people with Spinal Cord Injury
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Spinal cord injury (SCI) impairs sensorimotor pathways, reducing walking ability. Effects of sensorimotor impairments are complex due to interactions with other factors such as age, aids, injury level, and severity. Traditional regression analysis has commonly been used to capture the effects, but it assumes linearity and misses local feature impacts. Meanwhile, explainable AI methods like SHapley Addictive exPlanations (SHAP) can reveal feature importances globally and locally based on cooperative game theory. Additionally, Gaussian Process Regression (GPR) can handle limited data sets, a common challenge in medical studies with small sample sizes. In this study, we proposed and evaluated a framework applying GPR and SHAP to quantify how sensorimotor impairments impact post-SCI walking performance. Thirty four recruited individuals with SCI underwent a clinical assessment and a six-minute walk test with oxygen consumption measurement. We identified strong linear relationships between muscle strength and six-minute walk test performance wherein greater strength was associated with longer distance walked and lower energy costs. The findings also highlighted considerable impacts of walking aids and cardiovascular capacity on post-SCI mobility. Individual SHAP analyses quantified how neurological factors influenced walking performance for each participant. This study demonstrated that nonparametric regression and explainable AI could provide insights into the complex neurological factors affecting walking ability in persons with SCI.
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| 44. |
- Truong, Minh T.N. 1994-, et al.
(författare)
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Gait Stratification in People with Incomplete Spinal Cord Injury using Data-Driven Techniques
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Background: Incomplete spinal cord injury often causes heterogeneous locomotion function, depending on remaining sensorimotor functions below the injury. Standardized tests have limited ability to quantify diverse gait impairments. Combining clustering methods with dynamic time warping distances can objectively capture heterogeneous gait patterns without bias. Moreover, tree-based models with explainable AI can reveal important features often missed by traditional gait analyses. This study presents a framework to characterize gait heterogeneity in persons with incomplete spinal cord injury based on unsupervised learning and explainable AI. We aimed to stratify gait heterogeneity into clusters without priori identification of parameters, and to gain clinical insights into the derived clusters.Methods: A cohort of 28 individuals with incomplete spinal cord injury and 21 non-disabled control subjects were recruited. Individuals with incomplete spinal cord injury underwent physical assessment of lower extremity strength, sensory function, and spasticity. Both groups underwent 3D gait analysis. Multidimensional dynamic time warping and hierarchical agglomerative clustering were used to identify distinct gait subgroups after injury. A random forest classifier and TreeSHAP were used to identify gait predictors that distinguished each cluster from the controls. Results: Six distinct gait clusters were identified from 280 gait cycles. Walking speed and step length were smaller than controls in four clusters. Gait patterns in two clusters were relatively similar to those in control. Low maximal ankle plantarflexion during swing was found to be a common gait impairments in five of the six clusters. Overall muscle strength significantly differed between clusters.Conclusions: In this study, we describe a data-driven framework coupled with explainable AI to identify clusters of common gait patterns without priori parameter identification among the otherwise heterogeneous gait patterns in persons with spinal cord injury. This work represents an initial step in developing individualized rehabilitation programs for persons with incomplete spinal cord injury.
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| 45. |
- Wall, Anneli, et al.
(författare)
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Gait pattern after electromechanically-assisted gait training with the Hybrid Assistive Limb and conventional gait training in sub-acute stroke rehabilitation-A subsample from a randomized controlled trial
- 2023
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Ingår i: Frontiers in Neurology. - : Frontiers Media SA. - 1664-2295. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Electromechanically-assisted gait training has been introduced in stroke rehabilitation as a means to enable gait training with a large number of reproducible and symmetrical task repetitions, i.e. steps. However, few studies have evaluated its impact on gait pattern functions. This study includes persons with no independent ambulation function at the start of a 4-week neurorehabilitation period in the sub-acute phase after stroke. The primary aim of the study was to evaluate whether the addition of electromechanically-assisted gait training to conventional training resulted in better gait pattern function than conventional training alone. The secondary aim was to identify correlations between overall gait quality and standardized clinical assessments.Participants and methods: Seventeen patients with no independent ambulation function who participated in a Prospective Randomized Open Blinded End-point study in the sub-acute phase after stroke were randomized into two groups; one group (n = 7) to undergo conventional training only (CONV group) and the other group (n = 10) to undergo conventional training with additional electromechanically-assisted gait training (HAL group). All patients were assessed with 3D gait analysis and clinical assessments after the 4-week intervention period. Overall gait quality as per the Gait Profile Score (GPS), as well as kinematic, and kinetic and other spatiotemporal metrics were collected and compared between intervention groups. Correlations between biomechanical and clinical outcomes were evaluated.Results: Both the CONV and HAL groups exhibited similar gait patterns with no significant differences between groups in any kinematic, kinetic parameters or other spatiotemporal metrics. The GPS for the paretic limb had a median (IQR) of 12.9° (7.8°) and 13.4° (4.3°) for the CONV and HAL groups, respectively (p = 0.887). Overall gait quality was correlated with independence in walking, walking speed, movement function and balance. We found no added benefit in gait pattern function from the electromechanically-assisted gait training compared to the conventional training alone.Discussion: This finding raises new questions about how to best design effective and optimal post-stroke rehabilitation programs in patients with moderate to severe gait impairments to achieve both independent walking and optimal gait pattern function, and about which patients should be in focus in further studies on the efficacy of electromechanically-assisted gait training.Clinical trial registration: The study was retrospectively registered at ClinicalTrials.gov, identifier (NCT02410915) on April 2015.
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| 46. |
- Wang, Ruoli, et al.
(författare)
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The Effect of Step Width on Muscle Contributions to Body Mass Center Acceleration During the First Stance of Sprinting
- 2021
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Ingår i: Frontiers in Bioengineering and Biotechnology. - : Frontiers Media S.A.. - 2296-4185. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Background: At the beginning of a sprint, the acceleration of the body center of mass (COM) is driven mostly forward and vertically in order to move from an initial crouched position to a more forward-leaning position. Individual muscle contributions to COM accelerations have not been previously studied in a sprint with induced acceleration analysis, nor have muscle contributions to the mediolateral COM accelerations received much attention. This study aimed to analyze major lower-limb muscle contributions to the body COM in the three global planes during the first step of a sprint start. We also investigated the influence of step width on muscle contributions in both naturally wide sprint starts (natural trials) and in sprint starts in which the step width was restricted (narrow trials).Method: Motion data from four competitive sprinters (2 male and 2 female) were collected in their natural sprint style and in trials with a restricted step width. An induced acceleration analysis was performed to study the contribution from eight major lower limb muscles (soleus, gastrocnemius, rectus femoris, vasti, gluteus maximus, gluteus medius, biceps femoris, and adductors) to acceleration of the body COM.Results: In natural trials, soleus was the main contributor to forward (propulsion) and vertical (support) COM acceleration and the three vasti (vastus intermedius, lateralis and medialis) were the main contributors to medial COM acceleration. In the narrow trials, soleus was still the major contributor to COM propulsion, though its contribution was considerably decreased. Likewise, the three vasti were still the main contributors to support and to medial COM acceleration, though their contribution was lower than in the natural trials. Overall, most muscle contributions to COM acceleration in the sagittal plane were reduced. At the joint level, muscles contributed overall more to COM support than to propulsion in the first step of sprinting. In the narrow trials, reduced COM propulsion and particularly support were observed compared to the natural trials.Conclusion: The natural wide steps provide a preferable body configuration to propel and support the COM in the sprint starts. No advantage in muscular contributions to support or propel the COM was found in narrower step widths.
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| 47. |
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| 48. |
- Yadav, Priti, 1985-, et al.
(författare)
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Influence of loading direction due to physical activity on proximal femoral growth tendency
- 2021
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Ingår i: Medical Engineering and Physics. - : Elsevier BV. - 1350-4533 .- 1873-4030. ; 90, s. 83-91
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Tidskriftsartikel (refereegranskat)abstract
- Longitudinal bone growth is regulated by mechanical forces arising from physical activity, whose directions and magnitudes depend on activity kinematics and intensity. This study aims to investigate the influence of common physical activities on proximal femoral morphological tendency due to growth at the femoral head growth plate. A subject-specific femur model based on magnetic resonance images of one able-bodied 6-year old child was developed, and the directions of hip contact force were described as load samples at a constant magnitude. Finite element analysis was performed to predict growth rate and growth direction, and expected changes in neck-shaft angle and femoral anteversion were computed corresponding to circa 4 months of growth. For most loading conditions, neck-shaft angle and femoral anteversion decreased during growth, corresponding to the femur & rsquo;s natural course during normal growth. The largest reduction in neck-shaft angle and femoral anteversion was approximately 0.25 degrees and 0.15 degrees. Our results suggest that most common physical activities induce the expected morphological changes in normal growth in able-bodied children. Understanding the influence of contact forces during less common activities on proximal femoral development might provide improved guidelines and treatment planning for children who have or are at risk of developing a femoral deformity.
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| 49. |
- Yadav, Priti, 1985-, et al.
(författare)
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Influence of muscle groups' activation on proximal femoral growth tendency
- 2017
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Ingår i: Biomechanics and Modeling in Mechanobiology. - : SPRINGER HEIDELBERG. - 1617-7959 .- 1617-7940. ; 16:6, s. 1869-1883
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Tidskriftsartikel (refereegranskat)abstract
- Muscle and joint contact force influence stresses at the proximal growth plate of the femur and thus bone growth, affecting the neck shaft angle (NSA) and femoral anteversion (FA). This study aims to illustrate how different muscle groups' activation during gait affects NSA and FA development in able-bodied children. Subject-specific femur models were developed for three able-bodied children (ages 6, 7, and 11 years) using magnetic resonance images. Contributions of different muscle groups-hip flexors, hip extensors, hip adductors, hip abductors, and knee extensors-to overall hip contact force were computed. Specific growth rate for the growth plate was computed, and the growth was simulated in the principal stress direction at each element in the growth front. The predicted growth indicated decreased NSA and FA (of about over a four-month period) for able-bodied children. Hip abductors contributed the most, and hip adductors, the least, to growth rate. All muscles groups contributed to a decrease in predicted NSA (similar to 0.01 degrees-0.04 degrees and FA (similar to 0.004 degrees-0.2 degrees), except hip extensors and hip adductors, which showed a tendency to increase the FA (similar to 0.004 degrees-0.2 degrees). Understanding influences of different muscle groups on long bone growth tendency can help in treatment planning for growing children with affected gait.
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| 50. |
- Zhang, Longbin, et al.
(författare)
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Ankle Joint Torque Estimation Using an EMG-Driven Neuromusculoskeletal Model and an Artificial Neural Network Model
- 2021
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Ingår i: IEEE Transactions on Automation Science and Engineering. - : Institute of Electrical and Electronics Engineers (IEEE). - 1545-5955 .- 1558-3783. ; 18:2, s. 564-573
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Tidskriftsartikel (refereegranskat)abstract
- In recent decades, there has been an increasing interest in the use of robotic powered exoskeletons to assist patients with movement disorders in rehabilitation and daily life. Providing assistive torque that compensates for the user’s remaining muscle contributions is a growing and challenging field within exoskeleton control. In this article, ankle joint torques were estimated using electromyography (EMG)-driven neuromusculoskeletal (NMS) model and an artificial neural network (ANN) model in seven movement tasks, including fast walking, slow walking, self-selected speed walking, and isokinetic dorsi/plantar flexion at 60◦/s and 90◦/s . In each method, EMG signals and ankle joint angles were used as input, the models were trained with data from 3-D motion analysis, and ankle joint torques were predicted. Six cases using different motion trials as calibration (for the NMS model)/training (for the ANN) were devised, and the agreement between the predicted and measured ankle joint torques was computed. We found that the NMS model could overall better predict ankle joint torques from EMG and angle data than the ANN model with some exceptions; the ANN predicted ankle joint torques with better agreement when trained with data from the same movement. The NMS model predicted ankle joint torque best when calibrated with trials during which EMG reached maximum levels, whereas the ANN predicted well when trained with many trials and types of movements. In addition, the ANN prediction may become less reliable when predicting unseen movements. Detailed comparative studies of methods to predict ankle joint torque are crucial for determining strategies for exoskeleton control. Note to Practitioners—In exoskeleton control for strength augmentation applied in military, industry, and healthcare applications, providing assistive torque that compensates for the user’s remaining muscle contributions, is a challenging problem. This article predicted the ankle joint torques by electromyography (EMG)-driven neuromusculoskeletal (NMS) model and an artificial neural network (ANN) model in different movements. To the best of our knowledge, this is the first study comparing joint torque prediction performance of EMG-driven model to ANN. In the EMG-driven NMS model, mathematical equations were formulated to reproduce the transformations from EMG signal generation and joint angles to musculotendon forces and joint torques. A three-layer ANN was constructed with an adaptive moment estimation (Adam) optimization method to learn the relationships between the inputs (EMG signals and joint angles) and the outputs (joint torques). In the experiments, we estimated ankle joint torques in gait and isokinetic movements and compared the performance of methods to predict ankle joint torque, relating to how the methods have been calibrated/trained. The detailed analysis of the methods’ performance in predicting ankle joint torque can significantly contribute to determining which model to choose, and under which circumstances, and, thus, be of great benefit for exoskeleton rehabilitation controller design.
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