| 1. |
- Fröberg, Asa, et al.
(författare)
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High variability in strain estimation errors when using a commercial ultrasound speckle tracking algorithm on tendon tissue
- 2016
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Ingår i: Acta Radiologica. - : Sage Publications. - 0284-1851 .- 1600-0455. ; 57:10, s. 1223-1229
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Tidskriftsartikel (refereegranskat)abstract
- Background: Ultrasound speckle tracking offers a non-invasive way of studying strain in the free Achilles tendon where no anatomical landmarks are available for tracking. This provides new possibilities for studying injury mechanisms during sport activity and the effects of shoes, orthotic devices, and rehabilitation protocols on tendon biomechanics. Purpose: To investigate the feasibility of using a commercial ultrasound speckle tracking algorithm for assessing strain in tendon tissue. Material and Methods: A polyvinyl alcohol (PVA) phantom, three porcine tendons, and a human Achilles tendon were mounted in a materials testing machine and loaded to 4% peak strain. Ultrasound long-axis cine-loops of the samples were recorded. Speckle tracking analysis of axial strain was performed using a commercial speckle tracking software. Estimated strain was then compared to reference strain known from the materials testing machine. Two frame rates and two region of interest (ROI) sizes were evaluated. Results: Best agreement between estimated strain and reference strain was found in the PVA phantom (absolute error in peak strain: 0.21 +/- 0.08%). The absolute error in peak strain varied between 0.72 +/- 0.65% and 10.64 +/- 3.40% in the different tendon samples. Strain determined with a frame rate of 39.4Hz had lower errors than 78.6Hz as was the case with a 22mm compared to an 11mm ROI. Conclusion: Errors in peak strain estimation showed high variability between tendon samples and were large in relation to strain levels previously described in the Achilles tendon.
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| 2. |
- Ainegren, Mats, 1963-, et al.
(författare)
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Breathing resistance in automated metabolic systems is high in comparison with the Douglas Bag method and previous recommendations
- 2018
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Ingår i: Proceedings of the Institution of Mechanical Engineers, Part P. - : SAGE Publications. - 1754-3371. ; 232:2, s. 122-130
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to investigate the resistance (RES) to breathing in metabolic systems used for the distribution and measurement of pulmonary gas exchange. A mechanical lung simulator was used to standardize selected air flow rates ( , L/s). The delta pressure (∆p, Pa) between ambient air and the air inside the equipment was measured in the breathing valve’s mouthpiece adapter for four metabolic systems and four types of breathing valves. RES for the inspiratory and expiratory sides was calculated as RES = ∆p / , Pa/L/s. The results for RES showed significant (p < 0.05) between-group variance among the tested metabolic systems, as well as the breathing valves and between most of the completed . The lowest RES among the metabolic systems was found for a Douglas Bag system, with approximately half of the RES compared to the automated metabolic systems. The automated systems were found to have higher RES already at low in comparison to previous recommendations. For the hardware components, the highest RES was found for the breathing valves while the lowest RES was found for the hoses. Conclusion: The results showed that RES in metabolic systems can be minimized through conscious choices of system design and hardware components.
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| 3. |
- Arvidsson, Daniel, 1974, et al.
(författare)
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Re-examination of accelerometer data processing and calibration for the assessment of physical activity intensity.
- 2019
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Ingår i: Scandinavian Journal of Medicine and Science in Sports. - : John Wiley & Sons. - 0905-7188 .- 1600-0838. ; 29:10, s. 1442-1452
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Tidskriftsartikel (refereegranskat)abstract
- This review reexamines use of accelerometer and oxygen uptake data for assessment of activity intensity. Accelerometers capture mechanical work, while oxygen uptake captures the energy cost of this work. Frequency filtering needs to be considered when processing acceleration data. A too restrictive filter attenuates the acceleration signal for walking and, to a higher degree, for running. This measurement error affects shorter (children) more than taller (adults) individuals due to their higher movement frequency. Less restrictive filtering includes more movement related signals and provide measures that better capture mechanical work, but may include more noise. An optimal filter cut-point is determined where most relevant acceleration signals are included. Further, accelerometer placement affects what part of mechanical work being captured. While the waist placement captures total mechanical work and therefore contributes to measures of activity intensity equivalent by age and stature, the thigh and wrist placements capture more internal work and do not provide equivalent measures. Value calibration of accelerometer measures is usually performed using measured oxygen uptake with the metabolic equivalent of task (MET) as reference measure of activity intensity. However, the use of MET is not stringent and is not a measure of activity intensity equivalent by age and stature. A candidate measure is the mass-specific net oxygen uptake, VO2 net (VO2 tot - VO2 stand). To improve measurement of physical activity intensity using accelerometers, research developments are suggested concerning processing of accelerometer data, use of energy expenditure as reference for activity intensity, and calibration procedure with absolute versus relative intensity. This article is protected by copyright. All rights reserved.
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| 4. |
- Fridolfsson, Jonatan, 1992, et al.
(författare)
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Effects of Frequency Filtering on Intensity and Noise in Accelerometer-Based Physical Activity Measurements.
- 2019
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Ingår i: Sensors. - : MDPI. - 1424-8220. ; 19:9
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Tidskriftsartikel (refereegranskat)abstract
- In objective physical activity (PA) measurements, applying wider frequency filters than the most commonly used ActiGraph (AG) filter may be beneficial when processing accelerometry data. However, the vulnerability of wider filters to noise has not been investigated previously. This study explored the effect of wider frequency filters on measurements of PA, sedentary behavior (SED), and capturing of noise. Apart from the standard AG band-pass filter (0.29-1.63 Hz), modified filters with low-pass component cutoffs at 4 Hz, 10 Hz, or removed were analyzed. Calibrations against energy expenditure were performed with lab data from children and adults to generate filter-specific intensity cut-points. Free-living accelerometer data from children and adults were processed using the different filters and intensity cut-points. There was a contribution of acceleration related to PA at frequencies up to 10 Hz. The contribution was more pronounced at moderate and vigorous PA levels, although additional acceleration also occurred at SED. The classification discrepancy between AG and the wider filters was small at SED (1-2%) but very large at the highest intensities (>90%). The present study suggests an optimal low-pass frequency filter with a cutoff at 10 Hz to include all acceleration relevant to PA with minimal effect of noise.
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| 5. |
- Gullstrand, Lennart, et al.
(författare)
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Measurements of vertical displacement in running, a methodological comparison
- 2009
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Ingår i: Gait & Posture. - : Elsevier BV. - 0966-6362 .- 1879-2219. ; 30:1, s. 71-75
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Tidskriftsartikel (refereegranskat)abstract
- The aim was (1) to evaluate measurements of vertical displacements (V-disp) of a single point on sacrum as an estimate of the whole body centre of mass (CoM) V-disp during treadmill running and (2) to compare three methods for measuring this single point. These methods were based on a position transducer(PT), accelerometers (AMs) and an optoelectronic motion capture system. Criterion method was V-disp of the whole body CoM measured with the motion capture system. Thirteen subjects ran at 10, 12, 14, 16. 18, 20 and 22 km h(-1) with synchronous recordings with the three methods. Four measurements of the (V-disp) were derived: (1) V-disp of CoM calculated from a segment model consisting of 13 segments tracked with 36 reflective markets, (2) V-disp of the sacrum recorded with the PT, (3) V-disp of the sacrum Calculated from the AM, and (4) V-disp of the sacrum calculated as the mid point of two reflective markets (sacrum marker, SM) attached at the level of the sacral bone. The systematic discrepancy between the Measurements of sacrum V-disp and CoM V-disp varied between 0 and 1.5 mm and decreased with increasing running velocity and decreasing step duration. PT and SM measurements showed strong correlation, whereas the AM showed a variability increasing with velocity. The random discrepancy within each Subject was 7 mm for all three methods. In conclusion single-point recordings of the sacrum V-disp may be used to monitor changes in V-disp of CoM during treadmill running.
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| 6. |
- Maiwald, Christian, et al.
(författare)
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The effect of intracortical bone pin application on kinetics and tibiocalcaneal kinematics of walking gait
- 2017
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Ingår i: Gait & Posture. - : Elsevier BV. - 0966-6362 .- 1879-2219. ; 52, s. 129-134
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Tidskriftsartikel (refereegranskat)abstract
- Gait analysis using bone anchored markers requires local anaesthesia, which may affect subjects gait patterns.Kinetic and kinematic variables were collected using two protocols (skin vs. bone anchored markers).No systematic differences were found between the two protocols.We conclude that the validity of the recorded variables is not affected by local anaesthesia.Bone anchored markers using intracortical bone pins are one of the few available methods for analyzing skeletal motion during human gait in-vivo without errors induced by soft tissue artifacts. However, bone anchored markers require local anesthesia and may alter the motor control and motor output during gait. The purpose of this study was to examine the effect of local anesthesia and the use of bone anchored markers on typical gait analysis variables. Five subjects were analyzed in two different gait analysis sessions. In the first session, a protocol with skin markers was used. In the second session, bone anchored markers were added after local anesthesia was applied. For both sessions, three dimensional infrared kinematics of the calcaneus and tibia segments, ground reaction forces, and plantar pressure data were collected. 95% confidence intervals and boxplots were used to compare protocols and assess the data distribution and data variability for each subject. Although considerable variation was found between subjects, within-subject comparison of the two protocols revealed non-systematic effects on the target variables. Two of the five subjects walked at reduced gait speed during the bone pin session, which explained the between-session differences found in kinetic and kinematic variables. The remaining three subjects did not systematically alter their gait pattern between the two sessions. Results support the hypothesis that local anesthesia and the presence of bone pins still allow a valid gait pattern to be analyzed.
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| 7. |
- Zhou, Guang-Quan, et al.
(författare)
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Automatic Myotendinous Junction Tracking in Ultrasound Images with Phase-Based Segmentation.
- 2018
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Ingår i: BioMed Research International. - : Hindawi Limited. - 2314-6133 .- 2314-6141.
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Tidskriftsartikel (refereegranskat)abstract
- Displacement of the myotendinous junction (MTJ) obtained by ultrasound imaging is crucial to quantify the interactive length changes of muscles and tendons for understanding the mechanics and pathological conditions of the muscle-tendon unit during motion. However, the lack of a reliable automatic measurement method restricts its application in human motion analysis. This paper presents an automated measurement of MTJ displacement using prior knowledge on tendinous tissues and MTJ, precluding the influence of nontendinous components on the estimation of MTJ displacement. It is based on the perception of tendinous features from musculoskeletal ultrasound images using Radon transform and thresholding methods, with information about the symmetric measures obtained from phase congruency. The displacement of MTJ is achieved by tracking manually marked points on tendinous tissues with the Lucas-Kanade optical flow algorithm applied over the segmented MTJ region. The performance of this method was evaluated on ultrasound images of the gastrocnemius obtained from 10 healthy subjects (26.0±2.9 years of age). Waveform similarity between the manual and automatic measurements was assessed by calculating the overall similarity with the coefficient of multiple correlation (CMC). In vivo experiments demonstrated that MTJ tracking with the proposed method (CMC = 0.97±0.02) was more consistent with the manual measurements than existing optical flow tracking methods (CMC = 0.79±0.11). This study demonstrated that the proposed method was robust to the interference of nontendinous components, resulting in a more reliable measurement of MTJ displacement, which may facilitate further research and applications related to the architectural change of muscles and tendons. [ABSTRACT FROM AUTHOR]
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