Muscle activity adapts to anti-gravity posture during pedalling in persons with post-stroke hemiplegia

Brown, David A.; Kautz, Steven A.; Dairaghi, Christine A.

doi:10.1093/brain/120.5.825

Cited by 62 publications

(43 citation statements)

References 10 publications

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“…17,19,20 Therefore, increases in pedaling workload will consequently place greater demands on nonplegic leg muscles. Our work has shown that the nonplegic leg is usually capable of responding to the increased demands because the timing of muscle activity patterns is similar to that of control leg muscles and does not change with increased workload.…”

Section: Discussionmentioning

confidence: 99%

“…This technique has been reported elsewhere and has been used to identify one quadrant for each muscle group where inappropriate activity can occur (ie, SO3, MG1, VM3, RF3, BF1, SM1). 19,20 Inappropriately timed activity occurs during periods in the pedaling cycle when muscles are lengthening and hence doing negative work. 28 We visually examined individual, nonaveraged crank kinematics, kinetics, and EMG activity for general trends.…”

Section: Data Processing and Analysismentioning

confidence: 99%

“…[13][14][15]21 Mechanical measures of pedaling performance can characterize impairment in persons with hemiplegia. 19,20 To pedal at a given cadence and workload, the combined mechanical work done by the two limbs must be sufficient to overcome the resistive load. The net mechanical work done by the plegic leg represents the net contribution of the plegic limb and can be positive (the limb assists crank propulsion), negative (the limb resists crank propulsion), or zero.…”

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confidence: 99%

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Increased Workload Enhances Force Output During Pedaling Exercise in Persons With Poststroke Hemiplegia

Brown

Kautz

1998

Stroke

104

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Background and Purpose-A principle of poststroke rehabilitation is that effort should be avoided since it leads to increased spasticity and produces widespread associated abnormal reactions. Although weakness also contributes to movement dysfunction after a stroke, it has been feared that heightened activity levels during strength training will further exacerbate the abnormal tone imbalance present in spastic hemiplegia. The purpose of this study was to test this hypothesis by quantifying the effects of increased workload on motor performance during different speeds of pedaling exercise in persons with poststroke hemiplegia. Methods-Twelve healthy elderly subjects and 15 subjects with poststroke hemiplegia of greater than 6 months since onset were tested. The experimental protocol consisted of having subjects pedal at 12 randomly ordered workload and cadence combinations (45-J, 90-J, 135-J, and 180-J workloads at 25, 40, and 55 rpm). Pedal reaction forces were measured and used to calculate work done by each leg, including net positive and negative components. An electromyogram was recorded from seven leg muscles. Results-The main finding was that net mechanical work done by the plegic leg increased as workload increased in 75 of 81 instances without increasing the percentage of inappropriate muscle activity. Conclusions-This study provides evidence that persons with hemiplegia increase force output by their plegic limb when pedaling against higher workloads without exacerbation of impaired motor control. Therefore, exertional pedaling exercise is a beneficial intervention for achieving gains in muscular force output without worsening motor control impairments. (Stroke. 1998;29:598-606.)

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Section: Discussionmentioning

confidence: 99%

Section: Data Processing and Analysismentioning

confidence: 99%

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confidence: 99%

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Increased Workload Enhances Force Output During Pedaling Exercise in Persons With Poststroke Hemiplegia

Brown

Kautz

1998

Stroke

104

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“…Or synergies may be accessed from a variety of neuronal networks, which could account for differences in their modulation and changes with neurological impairments. Evidence from stroke and spinal cord patients during locomotion also suggest that higher centers may be necessary for appropriate synergies to arise (Bourbonnais et al 1989;Brown et al 1997;Ivanenko et al 2003).…”

Section: How Are Synergies Encoded In the Nervous System?mentioning

confidence: 99%

Muscle Synergy Organization Is Robust Across a Variety of Postural Perturbations

Torres-Oviedo¹,

Macpherson²,

Ting³

2006

Journal of Neurophysiology

428

402

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. We recently showed that four muscle synergies can reproduce multiple muscle activation patterns in cats during postural responses to support surface translations. We now test the robustness of functional muscle synergies, which specify muscle groupings and the active force vectors produced during postural responses under several biomechanically distinct conditions. We aimed to determine whether such synergies represent a generalized control strategy for postural control or if they are merely specific to each postural task. Postural responses to multidirectional translations at different fore-hind paw distances and to multidirectional rotations at the preferred stance distance were analyzed. Five synergies were required to adequately reconstruct responses to translation at the preferred stance distance-four were similar to our previous analysis of translation, whereas the fifth accounted for the newly added background activity during quiet stance. These five control synergies could account for Ͼ80% total variability or r 2 Ͼ 0.6 of the electromyographic and force tuning curves for all other experimental conditions. Forces were successfully reconstructed but only when they were referenced to a coordinate system that rotated with the limb axis as stance distance changed. Finally, most of the functional muscle synergies were similar across all of the six cats in terms of muscle synergy number, synergy activation patterns, and synergy force vectors. The robustness of synergy organization across perturbation types, postures, and animals suggests that muscle synergies controlling task-variables are a general construct used by the CNS for balance control. I N T R O D U C T I O NRecent findings suggest that the CNS simplifies motor control by constraining muscles to be activated in fixed groups, or synergies, where each synergy is defined as a set of muscles recruited by a single neural command signal. Complex muscle activation patterns in a wide range of motor tasks including locomotion, finger spelling, and postural tasks, can be decomposed into the summed activation of just a few muscle synergies d'Avella et al. 2003;Ivanenko et al. 2003Ivanenko et al. , 2004Krishnamoorthy et al. 2003;Poppele and Bosco 2003;Poppele et al. 2002;Ting and Macpherson 2005;Tresch et al. 1999;Weiss and Flanders 2004). A muscle synergy control structure provides an attractive simplifying strategy for the control of complex movements because it reduces the number of output patterns that the nervous system must specify for a large number of muscles yet allows flexibility in the final expression of muscle activation.A synergy control structure not only simplifies the motor output pattern for muscle activation but may also be functionally related to high-level control parameters-global biomechanical variables that are important for movement control. For example, Ting and Macpherson (2005) demonstrated in cats that four muscle synergies could account for the spatial tuning patterns of the automatic postural response elicited by support surface ...

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“…Moreover, when the model used only flexor and extensor synergies it was unable to advance the limb through the transition from extension to flexion (Raasch and Zajac, 1999). Similarly, stroke patients limited to flexion and extension synergies (Bourbonnais et al, 1989) have difficulties through the same phase transition (Brown et al, 1997). A similar model for understanding postural control would be critical to understanding the functional consequences of neural impairments that lead to balance disorders.…”

Section: Future Directionsmentioning

confidence: 99%

Dimensional reduction in sensorimotor systems: a framework for understanding muscle coordination of posture

Ting

2007

Progress in Brain Research

181

145

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The simple act of standing up is an important and essential motor behavior that most humans and animals achieve with ease. Yet, maintaining standing balance involves complex sensorimotor transformations that must continually integrate a large array of sensory inputs and coordinate multiple motor outputs to muscles throughout the body. Multiple, redundant local sensory signals are integrated to form an estimate of a few global, task-level variables important to postural control, such as body center of mass position and body orientation with respect to Earth-vertical. Evidence suggests that a limited set of muscle synergies, reflecting preferential sets of muscle activation patterns, are used to move task variables such as center of mass position in a predictable direction following a postural perturbations.We propose a hierarchal feedback control system that allows the nervous system the simplicity of performing goal-directed computations in task-variable space, while maintaining the robustness afforded by redundant sensory and motor systems. We predict that modulation of postural actions occurs in task-variable space, and in the associated transformations between the low-dimensional task-space and high-dimensional sensor and muscle spaces. Development of neuromechanical models that reflect these neural transformations between low and high-dimensional representations will reveal the organizational principles and constraints underlying sensorimotor transformations for balance control, and perhaps motor tasks in general. This framework and accompanying computational models could be used to formulate specific hypotheses about how specific sensory inputs and motor outputs are generated and altered following neural injury, sensory loss, or rehabilitation. KeywordsMuscle; balance; EMG; muscle synergy; motor control; biomechanics; feedback; sensorimotor integration Postural control is a fundamental motor task ideally suited for investigating questions of sensorimotor integration and redundancy. The ability to maintain posture and balance are precursors to other voluntary movements such as reaching or walking over uneven terrain. Moreover, loss of balance is a clinically important problem, as falls are a primary cause of injury and accidental death in older adults (Minino et al., 2002 NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript understanding of the underlying neuromechanical principles that govern patterns of muscle activation during postural control or other basic motor behaviors.Although technological advances allow the simultaneous measurement of multiple kinematic, kinetic, and electromyographic (EMG) data channels during behavioral experiments, we lack a framework for understanding how all of these measured variables are related to the control and performance of a functional task. Without this basic understanding, we cannot begin to understand or predict how patterns of muscle activation should be altered to perform novel tasks, nor can we understand the functional impact of di...

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Muscle activity adapts to anti-gravity posture during pedalling in persons with post-stroke hemiplegia

Cited by 62 publications

References 10 publications

Increased Workload Enhances Force Output During Pedaling Exercise in Persons With Poststroke Hemiplegia

Increased Workload Enhances Force Output During Pedaling Exercise in Persons With Poststroke Hemiplegia

Muscle Synergy Organization Is Robust Across a Variety of Postural Perturbations

Dimensional reduction in sensorimotor systems: a framework for understanding muscle coordination of posture

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