| 1. |
- Andersson, Eva A, et al.
(författare)
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Abdominal and hip flexor muscle activation during various training exercises.
- 1997
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Ingår i: European Journal of Applied Physiology and Occupational Physiology. - : Springer Science and Business Media LLC. - 0301-5548 .- 1432-1025 .- 1439-6319 .- 1439-6327. ; 75:2, s. 115-23
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to provide objective information on the involvement of different abdominal and hip flexor muscles during various types of common training exercises used in rehabilitation and sport. Six healthy male subjects performed altogether 38 different static and dynamic training exercises trunk and hip flexion sit-ups, with various combinations of leg position and support, and bi- and unilateral leg lifts. Myoelectric activity was recorded with surface electrodes from the rectus abdominis, obliquus externus, obliquus internus, rectus femoris, and sartorius muscles and with indwelling fine-wire electrodes from the iliacus muscle. The mean electromyogram amplitude, normalised to the highest observed value, was compared between static and dynamic exercises separately. The hip flexors were highly activated only in exercises involving hip flexion, either lifting the whole upper body or the legs. In contrast, the abdominal muscles showed marked activation both during trunk and hip flexion sit-ups. In hip flexion sit-ups, flexed and supported legs increased hip flexor activation, whereas such modifications did not generally alter the activation level of the abdominals. Bilateral, but not unilateral, leg lifts required activation of abdominal muscles. In trunk flexion sit-ups an increased activation of the abdominal muscles was observed with increased flexion angle, whereas the opposite was true for hip flexion sit-ups. Bilateral leg lifts resulted in higher activity levels than hip flexion sit-ups for the iliacus and sartorius muscles, while the opposite was true for rectus femoris muscles. These data could serve as a basis for improving the design and specificity of test and training exercises.
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| 2. |
- Andersson, Eva A
(författare)
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EMG and strength in trunk and hip muscles
- 1997
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The overall aim of this thesis was to study the myouelectric activity of all major muscles involved in the movements and stabilization of the trunk, pelvis and hips during training exercises, postures, motor tasks, maximal strength performance and locomotion. By use of ultra-sound, EMG electrodes could be guided safely and accurately into muscles situated even close to the spinal column, such as psoas, quadratus lumborum and deep parts of erector spinae. A task specific variation in activation levels were seen between muscle synergies, as well as between individual muscles within a synergy. Selective engagement of the abdominal muscles could be achieved in trunk flexion sit-ups, that is lifting only the upper trunk from the floor. An even higher activation of abdominal muscles was needed for static stabilization of the trunk and pelvis during hip flexion sit-ups, whereas single leg lifts were performed without involvement of the abdominal muscles. A selective activation of either the iliacus or psoas muscle was observed, for example in certain types of training exercises and in walking and running. Applying bending moments to the spine, resulted in a grading of the muscle activation response according to mechanical advantage, that is highest in the quadratus lumborum in lateral loading and in the superficial erector spinae in ventral loading. An exception was the most forward flexed position in standing where the superficial erector spinae "relaxed" but quadratus lumborum remained active. In general, the level of EMG in maximal efforts was maintained at the same high level irrespective of position in the range of motion, despite a marked variation in strength output. This position-dependency, as well as the strength values as such, varied in a specific way in groups of athletes, related to previous background. These data contribute to the understanding of muscle function and motor control of the trunk , pelvis and hips. They are also of relevance when evaluating and designing tests and training programs in rehabilitation and sport contexts as well as for improving biomechanical models of spinal loading.
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| 3. |
- Andersson, Eva A, et al.
(författare)
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Intramuscular EMG from the hip flexor muscles during human locomotion.
- 1997
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 161:3, s. 361-70
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Tidskriftsartikel (refereegranskat)abstract
- The purpose was to investigate the activation pattern of five major hip flexor muscles and its adaptation to changing speed and mode of progression. A total of 11 healthy subjects performed walking and running on a motor-driven treadmill at speeds ranging from 1.0 to 6.0 m s-1. Intramuscular fine-wire electrodes were used to record myoelectric signals from the iliacus, psoas, sartorius, rectus femoris and tensor fascia latae muscles. The basic pattern, with respect to number of activation periods, remained the same irrespective of speed and mode of progression. However, differences in the relative duration and timing of onset of activation occurred between individual muscles. Over the speed range in walking, a progressively earlier onset was generally seen for the activation period related to hip flexion. Changes in EMG amplitude were measured in the iliacus and psoas muscles and showed a marked increase and difference between walking and running at speeds above 2.0 m s-1. Thus, the alternating flexion-extension movements at the hip during locomotion appear to be governed by a rather fixed 'neural program' which normally only needs minor modulations to accomplish the adjustments accompanying an increase in speed of progression as well as a change from walking to running.
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| 4. |
- Andersson, Eva A, et al.
(författare)
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Relative EMG levels in training exercises for abdominal and hip flexor muscles.
- 1998
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Ingår i: Scandinavian Journal of Rehabilitation Medicine. - : Informa UK Limited. - 0036-5505 .- 1940-2228. ; 30:3, s. 175-83
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Tidskriftsartikel (refereegranskat)abstract
- The main purpose of our study was to compare systematically EMG levels in sub-maximal training exercises for the trunk and hip flexor muscles with those voluntarily attainable in corresponding situations. Six healthy subjects performed three types of standardized training exercises, whose static positions, movement velocity and range of motion were reproduced during maximal voluntary isokinetic strength tests. EMG was recorded with wire electrodes from the iliacus muscle and with surface electrodes from the rectus femoris, sartorius, rectus abdominis, obliquus externus and internus muscles. The relative EMG values demonstrated a task dependency which could differ between individual muscles. The maximal voluntary activation levels were relatively constant across conditions. Exceptions were present, particularly for the rectus femoris and iliacus muscles. These findings highlight the consequences of using different methods of normalizing EMG. The relative EMG values presented may serve as guidelines when selecting training exercises for specific trunk and hip flexor muscles in sports and rehabilitation.
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| 5. |
- Andersson, Eva, et al.
(författare)
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EMG activities of the quadratus lumborum and erector spinae muscles during flexion-relaxation and other motor tasks.
- 1996
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Ingår i: Clinical biomechanics (Bristol, Avon). - : Elsevier BV. - 1879-1271 .- 0268-0033. ; 11:7, s. 392-400
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: The aim of this study was to provide new information on the myoelectrical activation of the quadratus lumborum, the deep lateral and the superficial medial lumbar erector spinae, the psoas, and the iliacus muscles in various motor tasks. DESIGN: An intramuscular electromyographic study was performed. BACKGROUND: The contribution of individual deep trunk muscles to the stability of the lumbar spine is relatively unknown in different tasks, including the flexion-relaxation phenomenon. METHODS: Seven healthy subjects participated. Fine-wire electrodes were inserted with a needle guided by ultrasound. RESULTS: The highest activity observed for quadratus lumborum and deep lateral erector spinae occurred in ipsilateral trunk flexion in a side-lying position and for superficial medial erector spinae during bilateral leg lift in a prone position. Quadratus lumborum and deep lateral erector spinae were activated when the flexion-relaxation phenomenon was present for superficial medial erector spinae, i.e. when its activity ceased in the latter part of full forward flexion of the trunk, held relaxed and kyphotic. CONCLUSIONS: In general, the activation of the investigated muscles showed a high degree of task specificity, where activation of a certain muscle was not always predictable from its anatomical arrangement and mechanical advantage.
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| 6. |
- Andersson, Eva, et al.
(författare)
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The role of the psoas and iliacus muscles for stability and movement of the lumbar spine, pelvis and hip.
- 1995
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Ingår i: Scandinavian Journal of Medicine and Science in Sports. - 0905-7188 .- 1600-0838. ; 5:1, s. 10-6
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Tidskriftsartikel (refereegranskat)abstract
- The activation patterns of the psoas and iliacus muscles were investigated in 7 healthy adult subjects (4 men and 3 women) during a variety of motor tasks in standing, sitting and lying. Myoelectric activity was recorded simultaneously from the 2 muscles using thin wire electrodes inserted under guidance of high-resolution ultrasound. In general, both muscles were coactivated, albeit to different relative levels, particularly when hip flexor torque was required. Selective activation of the iliacus could, however, be seen to stabilize the pelvis in contralateral hip extension during standing. Psoas was found to be selectively involved in sitting with a straight back and in contralateral loading situations requiring stabilization of the spine in the frontal plane. During training exercises from a supine position, such as sit-ups, the contribution of the psoas and iliacus muscles could be varied by changing the range of motion as well as the position and support for the legs. Thus, the 2 anatomically different muscles of the iliopsoas complex were shown to have individual and task-specific activation patterns depending on the particular demands for stability and movement at the lumbar spine, pelvis and hip.
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| 7. |
- Cresswell, Andrew G, et al.
(författare)
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Influence of gastrocnemius muscle length on triceps surae torque development and electromyographic activity in man.
- 1995
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Ingår i: Experimental Brain Research. - 0014-4819 .- 1432-1106. ; 105:2, s. 283-90
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Tidskriftsartikel (refereegranskat)abstract
- The present study was designed to determine the relative contribution of the gastrocnemius muscle to isometric plantar flexor torque production at varying knee angles, while investigating the activation of the gastrocnemius muscle at standardised non-optimal lengths. Voluntary plantar flexor torque, supramaximally stimulated twitch torque and myoelectric activity (EMG) from the triceps surae were measured at different knee angles. Surface and intra-muscular EMG were recorded from the soleus muscle and the medial and lateral heads of the gastrocnemius muscle in 10 male subjects. With the ankle angle held constant, knee angle was changed in steps of 30 degrees ranging from 180 degrees (extended) to 60 degrees (extreme flexion), while voluntary torque from a 5-s contraction was determined at 10 different levels of voluntary effort, ranging from 10% of maximal effort to maximal effort. To assess effort, supramaximal twitches were superimposed on all voluntary contractions, and additionally during rest. Maximal plantar flexor torque and resting twitch torque decreased significantly in a sigmoidal fashion with increasing knee flexion to 60% of the maximum torque at 180 degrees knee angle. For similar levels of voluntary effort, the EMG root mean square (RMS) of gastrocnemius was less with increased knee flexion, whereas soleus RMS remained unchanged. From these data, it is concluded that the contribution of gastrocnemius to plantar flexor torque is at least 40% of the total torque in the straight leg position. The decrease of gastrocnemius EMG RMS with decreasing muscle length may be brought about by a decrease in the number of fibres within the EMG electrode recording volume and/or impaired neuromuscular transmission.
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| 8. |
- Daggfeldt, Karl, et al.
(författare)
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The role of intra-abdominal pressure in spinal unloading.
- 1997
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Ingår i: Journal of Biomechanics. - 0021-9290 .- 1873-2380. ; 30:11-12, s. 1149-55
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Tidskriftsartikel (refereegranskat)abstract
- Previous studies on how an increase in intra-abdominal pressure (IAP) effects the loading of the lumbar spine during back extension show diverging results. From a critical review of the literature we deduce a simplified, but consistent, model of the mechanisms involved in IAP-induced unloading of the lumbar spine. The model is then expanded by explicitly incorporating equilibrium equations for the pressurised abdomen and the abdominal wall. It is shown that the unloading effect of IAP can be viewed as that of a pressurised column of fixed cross-sectional area, between the rib cage and pelvis. Different abdominal forms are examined and a form with zero longitudinal curvature is found to have some important mechanical benefits for the generation of IAP-induced alleviation of compressive loading of the lumbar spine.
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| 9. |
- Hodges, Paul, et al.
(författare)
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Preparatory trunk motion accompanies rapid upper limb movement.
- 1999
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Ingår i: Experimental Brain Research. - : Springer Science and Business Media LLC. - 0014-4819 .- 1432-1106. ; 124:1, s. 69-79
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Tidskriftsartikel (refereegranskat)abstract
- Evaluation of trunk movements, trunk muscle activation, intra-abdominal pressure and displacement of centres of pressure and mass was undertaken to determine whether trunk orientation is a controlled variable prior to and during rapid bilateral movement of the upper limbs. Standing subjects performed rapid bilateral symmetrical upper limb movements in three directions (flexion, abduction and extension). The results indicated a small (0.4-3.3 degrees) but consistent initial angular displacement between the segments of the trunk in a direction opposite to that produced by the reactive moments resulting from limb movement. Phasic activation of superficial trunk muscles was consistent with this pattern of preparatory motion and with the direction of motion of the centre of mass. In contrast, activation of the deep abdominal muscles was independent of the direction of limb motion, suggesting a non-direction specific contribution to spinal stability. The results support the opinion that feedforward postural responses result in trunk movements, and that orientation of the trunk and centre of mass are both controlled variables in relation to rapid limb movements.
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| 10. |
- Huang, Q M, et al.
(författare)
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Pulling force in lateral lifting and lowering.
- 1998
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Ingår i: Ergonomics. - : Informa UK Limited. - 0014-0139 .- 1366-5847. ; 41:6, s. 899-908
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Tidskriftsartikel (refereegranskat)abstract
- This work investigated maximal voluntary lateral hand pulling force in 18 healthy, habitually active men. Measurements were made in standing at different static angles of lateral trunk flexion, as well as at different constant lifting and lowering velocities. Movement was constrained to the frontal plane, velocity was controlled by an isokinetic dynamometer, pulling force was measured with a strain gauge and overall lateral angular displacement of the trunk by an electrogoniometer. Mean peak pulling force values ranged from 478 to 658 N (static), 291 to 528 N (lifting), and 801 to 911 N (lowering), respectively. The static pulling forces were the highest in flexed positions to the loaded side (10 degrees and 20 degrees trunk angles). In lifting, peak and position-specific pulling force decreased with increasing velocity. Peak lifting force occurred in a flexed trunk position of 7 to 9 degrees to the loaded side. In lowering, pulling forces were significantly higher than during lifting at corresponding velocities and showed less changes with velocity. Peak lowering force occurred at a trunk angle of -7 to -11 degrees, that is towards the unloaded side. In conclusion, maximal voluntary pulling force in the frontal plane was found to be task dependent. Lowering was accompanied by higher forces and a different velocity and position dependency than lifting which, in addition to the fact that the trunk muscles act predominantly eccentrically during the lowering task, may impose an increased risk of injury.
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| 11. |
- Löscher, W N, et al.
(författare)
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Central fatigue during a long-lasting submaximal contraction of the triceps surae.
- 1996
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Ingår i: Experimental Brain Research. - 0014-4819 .- 1432-1106. ; 108:2, s. 305-14
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Tidskriftsartikel (refereegranskat)abstract
- Our purpose was to study central fatigue and its dependence on peripheral reflex inhibition during a sustained submaximal contraction of the triceps surae. In 11 healthy subjects, superimposed twitches, surface electromyograms (EMG) from the medial head of the gastrocnemius (MG) and soleus (SOL) muscles, maximal compound motor action potentials (M(max)), tracking error and tremor were recorded during sustained fatiguing contractions at a torque level corresponding to 30% of maximal voluntary contraction (MVC). When the endurance limit (401 +/- 91 s) of the voluntary contraction (VC-I) was reached, the triceps surae could be electrically stimulated to the same torque level for an additional 1 min in 10 of the 11 subjects. These subjects were then able to continue the contraction voluntarily (voluntary contraction II, VC-II) for another 85 +/- 48 s. At the endurance limit of VC-I, the superimposed twitch was larger than during the unfatigued MVC, while there was no significant difference between the twitch at the endurance limit of VC-II and MVC. The EMG amplitude of both MG and SOL at the endurance limit of VC-I was significantly less than that during the MVC. While the EMG amplitude of MG increased further during VC-II, SOL EMG remained unchanged, neither muscle reaching their unfatigued MVC values. This difference was diminished for SOL by taking into account its decrease in M(max) found during VC-II, and relative EMG levels approached their MVC values. These results clearly indicate that a higher voluntary muscle activation was achievable after 1 min of electrical muscle stimulation, which continued metabolic stress and contractile fatigue processes but allowed for supraspinal, muscle spindle and/or motoneuronal recovery. It is concluded that peripheral reflex inhibition of alpha-motoneurons via small-diameter muscle afferents is of minor significance for the development of the central fatigue that was found to occur during the first voluntary contraction.
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| 12. |
- Löscher, W N, et al.
(författare)
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Excitatory drive to the alpha-motoneuron pool during a fatiguing submaximal contraction in man.
- 1996
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Ingår i: Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 491 ( Pt 1), s. 271-80
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Tidskriftsartikel (refereegranskat)abstract
- 1. This study was undertaken to examine changes of excitatory drive to the triceps surae alpha-motoneuron pool during fatiguing submaximal isometric contractions in man. Eight healthy subjects maintained isometric plantar flexions at 30 percent of maximum voluntary contraction (MVC) until the limit of endurance (range, 6-9 min). 2. Excitability of the alpha-motoneuron pool to Ia afferent stimulation (H reflex), electromyograms (EMG) and maximum compound motor unit action potentials (Mmax) from the lateral (LG) and medial heads (MG) of the gastrocnemius as well as from the soleus muscle (Sol) were recorded throughout the contraction. Superimposed maximum twitch torques (twitch occlusion) and isometric torque fluctuations (tremor) were also recorded as indirect measures of excitatory drive. 3. H reflexes were studied at different levels of underlying voluntary contraction to assess the relationship between H reflex amplitude and excitatory drive. With increasing levels of underlying contraction up to MVC, superimposed H reflex amplitude increased for LG in six subjects, for MG in all eight and for Sol in five. In the remaining cases, H reflex amplitude first increased and then plateaued between 30-50% of MVC. 4. H/Mmax ratios increased during fatigue in those muscles that showed an H reflex amplitude increase with high levels of underlying contraction. In these cases, LG and MG H/Mmax increased significantly after about 50 and 20% of endurance time onward, respectively, whereas Sol H/Mmax demonstrated a significant increase up to 40% of endurance time. 5. EMG root mean square (r.m.s.) increased linearly throughout the contraction for all three muscles, while tremor r.m.s. increased in a non-linear way, with a steeper increase from 60% of endurance time onward. Superimposed twitch amplitude decreased significantly from 25% of endurance time onward. 6. It is concluded that during fatiguing isometric contractions at 30% of MVC, the excitatory drive to the triceps surae alpha-motoneuron pool increases. This is thought to be a compensatory mechanism to facilitate recruitment of new, unfatigued motor units (MUs), and/or to increase MU firing rates. The facts that the twitch is not abolished at endurance limit and that the EMG does not attain its unfatigued MVC level are strong indications that central fatigue occurred during the sustained submaximal contraction.
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| 13. |
- Löscher, W N, et al.
(författare)
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Recurrent inhibition of soleus alpha-motoneurons during a sustained submaximal plantar flexion.
- 1996
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Ingår i: Electroencephalography and Clinical Neurophysiology. - 0013-4694. ; 101:4, s. 334-8
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Tidskriftsartikel (refereegranskat)abstract
- During 10 min of sustained isometric plantar flexion at 20% of maximal voluntary contraction, recurrent inhibition of soleus alpha-motoneurons was studied in 9 healthy subjects (age 22-37 years). Recurrent inhibition was brought about by a conditioning H-reflex and assessed by a test H-reflex delivered 10 ms later. The amplitude of the test H-reflex during the tenth minute of the contraction (16.9 +/- 13.2% of the maximal compound motor action potential) was significantly increased as compared to that during the first minute (9.8 +/- 7.6%), while the conditioning H-reflex remained unchanged. Concomitantly, muscle fatigue was evidenced by a significant increase in amplitude of the soleus electromyogram. The increase of the test-H-reflex amplitude implies that a decrease in recurrent inhibition occurred during the sustained submaximal contraction, which contrasts results from studies on maximal voluntary contractions. These results indicate a modulation of soleus Renshaw interneurons, which is likely to serve the purpose of optimising motor unit recruitment and firing rates of this muscle during a sustained submaximal contraction.
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| 14. |
- Oddsson, L I, et al.
(författare)
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Interaction between voluntary and postural motor commands during perturbed lifting.
- 1999
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Ingår i: Spine. - : Ovid Technologies (Wolters Kluwer Health). - 0362-2436 .- 1528-1159. ; 24:6, s. 545-52
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Tidskriftsartikel (refereegranskat)abstract
- STUDY DESIGN: An experimental study was conducted to evaluate the effect of an unexpected postural perturbation during a lifting task. OBJECTIVES: To investigate electromyographic responses in the erector spinae to a postural perturbation, simulating slipping, during an ongoing voluntary lifting movement. It was hypothesized that specific combinations of voluntary movement and postural perturbation present a situation in which injury caused by a rapid switch between conflicting motor commands can occur. SUMMARY OF BACKGROUND DATA: Studies of postural perturbations have mainly focused on behavior during static tasks such as quiet, upright standing. To date, there are no published studies of the effect of a perturbation during an ongoing voluntary lifting movement. METHODS: Subjects standing on a movable platform were exposed to random perturbations while lifting a 20-kg load. Muscle activity was recorded from flexor and extensor muscles of the trunk and hip. Trunk flexion angle in the sagittal plane was recorded with a video system. RESULTS: Perturbations forward were followed by an increased activity in erector spinae superimposed on the background activation present during the lift, indicating that both the voluntary and postural motor programs caused an activation of erector spinae. During backward perturbation, however, there was a sudden cessation of erector spinae activity followed by an extended period of rapid electromyographic amplitude fluctuations while the trunk was flexing, indicating an eccentric contraction of the erector spinae. CONCLUSIONS: This erratic behavior with large electromyographic amplitude fluctuations in the erector spinae after a backward slip during lifting may indicate a rapid switch between voluntary and postural motor programs that require conflicting functions of the back muscles. This may cause rapid force changes in load-carrying tissue, particularly in those surrounding the spine, thus increasing the risk of slip-and-fall-related back injuries.
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| 15. |
- Seger, Jan
(författare)
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Neuromuscular aspects of eccentric knee extensor actions : effects of electrical stimulation, age, gender and training
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The overall aim of this thesis was to study the effects of electrical stimulation, age, gender and training on the torque- and EMG-velocity relationships during eccentric knee extensor muscle actions in man. An isokinetic custom-built dynamometer was evaluated and used throughout the thesis. During maximal voluntary efforts eccentric torque output was similar to isometric and did not change with velocity. Superimposing electrical stimulation onto a maximal effort caused a specific increase in eccentric torque output. Submaximal electrical stimulation alone also produced a relatively higher eccentric than concentric torque. These results indicate the presence of a neural tension-regulating mechanism during maximal voluntary eccentric muscle actions in man. The hypothesis that such a mechanism would be more pronounced in children than adultswas not corroborated by the results from children, pre- and postpuberty. The adult pattern of interdependence between torque, EMG and muscle action type seemed to be established before puberty in both males and females. Comparisons between genders indicated a higher eccentric to concentric ratio of electromechanical eficiency at high velocity in postpuberty and adult females. Training with either pure eccentric or concentric maximal isokinetic muscle actions resulted in mode and velocity specific adaptations, particularly for eccentric training, in peak torque, muscle cross-sectional area, electromechanical efficiency and cross education, that is increase in strength of the contralateral leg. On the other hand, no or only minor training effects were seen on mean torque, muscle fibre morphology, eccentric to concentric EMG ratios and antagonist muscle activity. The expression of net eccentric torque output during maximal voluntary eccentric knee extensor actions have shown several distinct features separating it from concentric and isometric actions. Clarification of the underlying neuromuscular mechanisms remains a challenge for future research.
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| 16. |
- Seger, Jan, et al.
(författare)
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Specific effects of eccentric and concentric training on muscle strength and morphology in humans.
- 1998
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Ingår i: European Journal of Applied Physiology. - 1439-6319 .- 1439-6327. ; 79, s. 49-57
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to compare pure eccentric and concentric isokinetic training with respect to their possible specificity in the adaptation of strength and morphology of the knee extensor muscles. Ten moderately trained male physical education students were divided into groups undertaking eccentric (ETG) and concentric (CTG) training. They performed 10 weeks of maximal isokinetic (90 degrees x s(-1)) training of the left leg, 4x10 repetitions - three times a week, followed by a second 10-week period of similar training of the right-leg. Mean eccentric and concentric peak torques increased by 18% and 2% for ETG and by 10% and 14% for CTG, respectively. The highest increase in peak torque occurred in the eccentric 90 degrees x s(-1) test for ETG (35%) whereas in CTG strength gains ranged 8%-15% at velocities equal or lower than the training velocity. Significant increases in strength were observed in the untrained contra-lateral leg only at the velocity and mode used in ipsilateral training. Cross-sectional area of the quadriceps muscle increased 3%-4% with training in both groups, reaching statistical significance only in ETG. No major changes in muscle fibre composition or areas were detected in biopsies from the vastus lateralis muscle for either leg or training group. In conclusion, effects of eccentric training on muscle strength appeared to be more mode and speed specific than corresponding concentric training. Only minor adaptations in gross muscle morphology indicated that other factors, such as changes in neural activation patterns, were causing the specific training-induced gains in muscle strength.
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| 17. |
- Stokes, V P, et al.
(författare)
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Dominant pattern extraction from 3-D kinematic data.
- 1999
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Ingår i: IEEE Transactions on Biomedical Engineering. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9294 .- 1558-2531. ; 46:1, s. 100-6
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Tidskriftsartikel (refereegranskat)abstract
- A new method for the extraction of a repeating pattern in cyclic biomechanical data is proposed--singular value decomposition pattern analysis (SVDPA). This method is based on the recent work of Kanjilal and Palit [14], [15] and can be applied to both contiguous and repeated trials without being constrained to be strictly periodic. SVDPA is a data-driven approach that does not use a preselected set of basis functions; but instead utilizes a data matrix with a special structure to identify repeating patterns. Several important features of SVDPA are described including its close relationship to the Kahunen-Loève transform. The dominant pattern is defined as the average energy component (AEC). The AEC is obtained from the SVD of the data matrix and is equivalent to the optimal [maximal signal-to-noise ratio (SNR)] ensemble average pattern. The degree of periodicity and SNR for the AEC are defined explicitly from the singular values of the data matrix. We illustrate the usefulness of SVDPA for dominant pattern extraction by applying it to the quasiperiodic three-dimensional trajectory of a marker attached to the trunk during treadmill locomotion. The AEC obtained for the normalized trajectory and error estimates at each point suggests that SVDPA could be a useful tool for the extraction of the fine details from cyclic biomechanical data.
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| 18. |
- Stokes, V P, et al.
(författare)
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From stride period to stride frequency.
- 1998
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Ingår i: Gait & posture. - 1879-2219. ; 7:1, s. 35-38
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Tidskriftsartikel (refereegranskat)abstract
- The stride-cycle frequency of gait data is often estimated by taking the inverse of the average stride-cycle time (stride period) over several stride-cycles. We derive the density function of the stride-cycle frequency frequency (stride frequency) and describe some of its properties. We also show the conditions under which the inverse of the mean stride period is a 'good' estimate of the mean stride frequency. Copyright 1998 Elsevier Science B.V.
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