Contribution of sensory feedback to plantar flexor muscle activation during push-off in adults with cerebral palsy

Exaggerated sensory activity has been assumed to contribute to functional impairment following lesion of the central motor pathway. However, recent studies have suggested that sensory contribution to muscle activity during gait is reduced in stroke patients and children with cerebral palsy (CP). We investigated whether this also occurs in CP adults and whether daily treadmill training is accompanied by alterations in sensory contribution to muscle activity. Seventeen adults with CP and 12 uninjured individuals participated. The participants walked on a treadmill while a robotized ankle-foot orthosis applied unload perturbations at the ankle, thereby removing sensory feedback naturally activated during push-off. Reduction of electromyographic (EMG) activity in the soleus muscle caused by unloads was compared and related to kinematics and ankle joint stiffness measurements. Similar measures were obtained after 6 wk of gait training. We found that sensory contribution to soleus EMG activation was reduced in CP adults compared with uninjured adults. The lowest contribution of sensory feedback was found in participants with lowest maximal gait speed. This was related to increased ankle plantar flexor stiffness. Six weeks of gait training did not alter the contribution of sensory feedback. We conclude that exaggerated sensory activity is unlikely to contribute to impaired gait in CP adults, because sensory contribution to muscle activity during gait was reduced compared with in uninjured individuals. Increased passive stiffness around the ankle joint is likely to diminish sensory feedback during gait so that a larger part of plantar flexor muscle activity must be generated by descending motor commands.NEW & NOTEWORTHY Findings suggest that adults with cerebral palsy have less contribution of sensory feedback to ongoing soleus muscle activation during push-off than uninjured individuals. Increased passive stiffness around the ankle joint is likely to diminish sensory feedback during gait, and/or sensory feedback is less integrated with central motor commands in the activation of spinal motor neurons. Consequently, muscle activation must to a larger extent rely on descending drive, which is already decreased because of the cerebral lesion.

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Contribution of corticospinal drive to ankle plantar flexor muscle activation during gait in adults with cerebral palsy

Experimental Brain Research ◽

10.1007/s00221-019-05520-3 ◽

2019 ◽

Vol 237 (6) ◽

pp. 1457-1467

Author(s):

Rasmus Feld Frisk ◽

Jakob Lorentzen ◽

Jens Bo Nielsen

Keyword(s):

Cerebral Palsy ◽

Muscle Activation ◽

Plantar Flexor ◽

Flexor Muscle

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Effects of plantar flexor muscle weakness on children with spastic cerebral palsy – Pilot study

Gait & Posture ◽

10.1016/j.gaitpost.2020.08.068 ◽

2020 ◽

Vol 81 ◽

pp. 340-341

Author(s):

R. Sert ◽

N.E. Akalan ◽

K. Onerge ◽

C. Sardogan ◽

F. Bilgili

Keyword(s):

Cerebral Palsy ◽

Pilot Study ◽

Muscle Weakness ◽

Spastic Cerebral Palsy ◽

Plantar Flexor ◽

Flexor Muscle

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Evaluation of an adjustable support shoulder exoskeleton on static and dynamic overhead tasks

Proceedings of the Human Factors and Ergonomics Society Annual Meeting ◽

10.1177/1541931218621184 ◽

2018 ◽

Vol 62 (1) ◽

pp. 804-808 ◽

Cited By ~ 8

Author(s):

Logan Van Engelhoven ◽

Nathan Poon ◽

Homayoon Kazerooni ◽

Alan Barr ◽

David Rempel ◽

...

Keyword(s):

Muscle Activity ◽

Muscle Activation ◽

Peak Torque ◽

Industrial Workers ◽

Human Engineering ◽

Shoulder Injuries ◽

Flexor Muscle ◽

Work Related ◽

Upper Trapezius ◽

Shoulder Complex

Introduction: Overhead tasks increase the risk of work related musculoskeletal disorders to industrial workers. A shoulder supporting exoskeleton with adjustable and angle dependent torque (referred to as shoulderX in this paper for brevity) was designed and built at the University of California Berkeley Human Engineering and Robotics Laboratory for workers performing overhead tasks. shoulderX was designed specifically to reduce the exposure to large muscle exertion forces on the shoulder complex from overhead work. Methods: We evaluated shoulderX by measuring the muscle activation of the upper trapezius (UT), anterior deltoid (AD), triceps long head (TR), and infraspinatus (IF) during static and dynamic overhead tasks. Thirteen male subjects with experience in the construction or manufacturing industries were recruited to perform overhead tasks using light (.45 kg) and heavy (2.25 kg) weight tools with four exoskeleton support levels (0, 8.5, 13.0, 20.0 Nm peak torque). Results: During all conditions, the wearer’s shoulder flexor muscle activity of UT, AD were reduced with increasing strength of shoulderX by up to 80%. Subjects unanimously preferred the use of shoulderX over the unassisted condition for all task types (static and dynamic overhead tasks) and tool weights (.45 kg and 2.25 kg). Conclusion: shoulderX reduces the wearer’s primary muscle activity in overhead static and dynamic work and results in a more desirable and balanced pattern of shoulder complex activation. This investigation indicates that shoulderX reduces the risk of work related shoulder injuries during overhead tasks.

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The primary afferent activity cannot capture the dynamical features of muscle activity during reaching movements

10.1101/138859 ◽

2017 ◽

Author(s):

Russell L. Hardesty ◽

Matthew T. Boots ◽

Sergiy Yakovenko ◽

Valeriya Gritsenko

Keyword(s):

Muscle Activity ◽

Sensory Feedback ◽

Muscle Activation ◽

Activity Patterns ◽

Afferent Feedback ◽

Reaching Movements ◽

Afferent Activity ◽

Primary Afferent ◽

Limb Dynamics ◽

Dynamical Features

AbstractThe stabilizing role of sensory feedback in relation to realistic 3-dimensional movement dynamics remains poorly understood. The objective of this study was to quantify how primary afferent activity contributes to shaping muscle activity patterns during reaching movements. To achieve this objective, we designed a virtual reality task that guided healthy human subjects through a set of planar reaching movements with controlled kinematic and dynamic conditions that minimized inter-subject variability. Next, we integrated human upper-limb models of musculoskeletal dynamics and proprioception to analyze motion and major muscle activation patterns during these tasks. We recorded electromyographic and motion-capture data and used the integrated model to simulate joint kinematics, joint torques due to muscle contractions, muscle length changes, and simulated primary afferent feedback. The parameters of the primary afferent model were altered systematically to evaluate the effect of fusimotor drive. The experimental and simulated data were analyzed with hierarchical clustering. We found that the muscle activity patterns contained flexible task-dependent groups that consisted of co-activating agonistic and antagonistic muscles that changed with the dynamics of the task. The activity of muscles spanning only the shoulder generally grouped into a proximal cluster, while the muscles spanning the wrist grouped into a distal cluster. The bifunctional muscle spanning the shoulder and elbow were flexibly grouped with either proximal or distal cluster based on the dynamical requirements of the task. The composition and activation of these groups reflected the relative contribution of active and passive forces to each motion. In contrast, the simulated primary afferent feedback was most related to joint kinematics rather than dynamics, even though the primary afferent models had nonlinear dynamical components and variable fusimotor drive. Simulated physiological changes to the fusimotor drive were not sufficient to reproduce the dynamical features in muscle activity pattern. Altogether, these results suggest that sensory feedback signals are in a different domain from that of muscle activation signals. This indicates that to solve the neuromechanical problem, the central nervous system controls limb dynamics through task-dependent co-activation of muscles and non-linear modulation of monosynaptic primary afferent feedback.New & NoteworthyHere we answered the fundamental question in sensorimotor transformation of how primary afferent signals can contribute to the compensation for limb dynamics evident in muscle activity. We combined computational and experimental approaches to create a new experimental paradigm that challenges the nervous system with passive limb dynamics that either assists or resists the desired movement. We found that the active dynamical features present in muscle activity are unlikely to arise from direct feedback from primary afferents.

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Increased Ankle Plantar Flexor Stiffness Is Associated With Reduced Mechanical Response to Stretch in Adults With CP

Frontiers in Bioengineering and Biotechnology ◽

10.3389/fbioe.2021.604071 ◽

2021 ◽

Vol 9 ◽

Author(s):

Jakob Lorentzen ◽

Rasmus Feld Frisk ◽

Jens Bo Nielsen ◽

Lee Barber

Keyword(s):

Ankle Joint ◽

Stretch Reflex ◽

Gastrocnemius Muscle ◽

Length Change ◽

Medial Gastrocnemius ◽

Reflex Response ◽

Plantar Flexor ◽

Flexor Muscle ◽

Muscle Fascicles ◽

Medial Gastrocnemius Muscle

Hyperexcitable stretch reflexes are often not present despite of other signs of spasticity in people with brain lesion. Here we looked for evidence that increased resistance to length change of the plantar flexor muscle-fascicles may contribute to a reduction in the stretch reflex response in adults with cerebral palsy (CP). A total of 17 neurologically intact (NI) adults (mean age 36.1; 12 female) and 13 ambulant adults with CP (7 unilateral; mean age 33.1; 5 female) participated in the study. Subjects were seated in a chair with the examined foot attached to a foot plate, which could be moved by a computer-controlled electromotor. An ultrasound probe was placed over the medial aspect of the leg to measure the length of medial gastrocnemius muscle fascicles. Slow (7 deg/s) and fast (200 deg/s) stretches with amplitude 6 deg of the plantar flexors were applied over an ankle range of 70 deg at 10 deg intervals between 60 and 130 deg plantarflexion. It was checked by EMG electrodes that the slow stretches were sufficiently slow not to elicit any activity and that the fast stretches were sufficiently quick to elicit a maximal stretch reflex in both groups. The torque elicited by the stretches was measured together with changes in the length of medial gastrocnemius muscle fascicles. Muscle fascicles increased significantly in length with increasing dorsiflexion position in both populations (p < 0.001), but the fascicles were shorter in the CP population at all positions. Slow stretches elicited significantly larger torque and significantly smaller length change of muscle fascicles as the ankle joint position was moved more towards dorsiflexion in CP than in NI (p < 0.001). Fast stretches elicited larger torque responses at ankle joint positions of 80–100 deg in the NI than in the CP group (p < 0.01). A significant negative correlation was observed between the torque response and muscle fascicle length change to slow stretch in CP (p < 0.05), but not in NI. These findings support that increased passive resistance of the ankle plantar flexor muscle-tendon unit and development of contractures may conceal stretch reflex response in adults with CP. We argue that this should be taken into account in the neurological examination of spasticity.

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Association between plantar flexor muscle volume and dorsiflexion flexibility in healthy young males: ultrasonography and magnetic resonance imaging studies

BMC Sports Science Medicine and Rehabilitation ◽

10.1186/s13102-021-00233-z ◽

2021 ◽

Vol 13 (1) ◽

Author(s):

Tadashi Suga ◽

Masafumi Terada ◽

Keigo Tomoo ◽

Yuto Miyake ◽

Takahiro Tanaka ◽

...

Keyword(s):

Magnetic Resonance Imaging ◽

Magnetic Resonance ◽

Muscle Volume ◽

Muscle Size ◽

Plantar Flexor ◽

Passive Stiffness ◽

Resonance Imaging ◽

Flexor Muscle ◽

Joint Flexibility ◽

Young Males

Abstract Background Although joint flexibility is important for human locomotion, the determinants of joint flexibility are not fully understood. In this study, we examined the relationship between dorsiflexion flexibility and plantar flexor muscle size in healthy young males. Methods and results The dorsiflexion flexibility was assessed using range of motion (ROM) and stiffness during active and passive dorsiflexion. Active ROM was defined as the maximal angle during voluntary dorsiflexion. Passive ROM was defined as the angle at the onset of pain during passive dorsiflexion. Passive stiffness was calculated as the slope of the linear portion of the torque-angle curve between 10º and 20º dorsiflexion of the ankle during passive dorsiflexion. In the first study, the plantar flexor muscle volume (MV) in 92 subjects was estimated on the basis of the lower leg length and plantar flexor muscle thickness, as measured using ultrasonography. The estimated plantar flexor MV correlated significantly with active ROM (r = -0.433), passive ROM (r = -0.299), and passive stiffness (r = 0.541) during dorsiflexion (P = 0.01 for all). In the second study, the plantar flexor MV in 38 subjects was measured using magnetic resonance imaging. The plantar flexor MV correlated significantly with plantar flexor active ROM (r = -0.484), passive ROM (r = -0.383), and passive stiffness (r = 0.592) during dorsiflexion (P = 0.05 for all). Conclusions These findings suggest that a larger plantar flexor MV is related to less dorsiflexion flexibility in healthy young males.

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Triceps surae torque-length relationships relevant for walking activity levels with and without an ankle exoskeleton

10.1101/778175 ◽

2019 ◽

Author(s):

Anthony L. Hessel ◽

Brent J. Raiteri ◽

Michael J. Marsh ◽

Daniel Hahn

Keyword(s):

Muscle Activity ◽

Metabolic Cost ◽

Activity Levels ◽

Plantar Flexor ◽

Plantar Flexors ◽

Flexor Muscle ◽

Fascicle Length ◽

Lateral Gastrocnemius ◽

Work Requirements ◽

Ankle Exoskeleton

AbstractAnkle exoskeletons have been developed to assist walking by offloading the plantar flexors work requirements, which reduces muscle activity level. However, reduced muscle activity alters plantar flexor muscle-tendon unit dynamics in a way that is poorly understood. We therefore evaluated torque-fascicle length properties of the soleus and lateral gastrocnemius during voluntary contractions at simulated activity levels typical during late stance with and without an ankle exoskeleton. Soleus activity levels (100, 30, and 22% maximal voluntary activity) were produced by participants via visual electromyography feedback at ankle angles ranging from −10° plantar flexion to 35° dorsiflexion. Using dynamometry and ultrasound imaging, torque-fascicle length data of the soleus and lateral gastrocnemius were produced. The results indicate that muscle activity reductions observed with an exoskeleton shift the torque-angle and torque-fascicle length curves to more dorsiflexed ankle angles and longer fascicle lengths where no descending limb is physiologically possible. This shift is in line with previous simulations that predicted a similar increase in the operating fascicle range when wearing an exoskeleton. These data suggest that a small reduction in muscle activity causes changes to torque-fascicle length properties, which has implications for the design and testing of future ankle exoskeletons for assisted walking.Significance StatementAssistive lower-limb exoskeletons reduce the metabolic cost of walking by reducing the positive work requirements of the plantar flexor muscles. However, if the exoskeleton reduces plantar flexor muscle activity too much, then the metabolic benefit is lost. The biological reasons for this are unclear and hinder further exoskeleton development. This research study is the first to directly evaluate if a reduction in plantar flexor muscle activity similar to that caused by wearing an exoskeleton affects muscle function. We found that reduced muscle activity changes the torque-length properties of two plantar flexors, which could explain why reducing muscle activity too much can increase metabolic cost.

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Predictors of Treatment Response to Progressive Resistance Training for Adolescents with Cerebral Palsy

Physical Therapy ◽

10.1093/ptj/pzab202 ◽

2021 ◽

Author(s):

Nicola Theis ◽

Marika Noorkoiv ◽

Grace Lavelle ◽

Jennifer Ryan

Keyword(s):

Cerebral Palsy ◽

Resistance Training ◽

Muscle Strength ◽

Training Program ◽

Muscle Activation ◽

Controlled Trial ◽

Progressive Resistance Training ◽

Flexor Muscle ◽

Resistance Training Program ◽

Progressive Resistance

Abstract Objective The aim of the study was to examine the variability in plantar-flexor muscle strength changes after progressive resistance training for adolescents with cerebral palsy (CP) and to identify baseline variables associated with change in muscle strength. Methods Thirty-three adolescents with CP were randomized to a 10-week progressive resistance training program as part of a randomized controlled trial (STAR trial). The associations between muscle strength at 10 weeks (n = 30 adolescents) and 22 weeks (n = 28 adolescents) and biomechanical and neuromuscular baseline characteristics, motor function, and fidelity to the program were examined with multivariable linear regression. Conclusion Assessing levels of muscle activation may be able to identify responders to a progressive resistance training program for adolescents with CP. These findings are a first step toward developing tools that can inform decision making in the clinical setting. Impact Due to the heterogenous nature of CP, it is challenging to assess the efficacy of strength training programs in individuals with CP and to understand the variability in outcomes among participants. This study provides a better understanding of the factors that predict response to an exercise program so that resistance training can be directed to those who will potentially benefit from it. Lay Summary There is wide variability in how well young people with CP respond to resistance training. If you are a young person with CP, your physical therapist can measure the amount of your gastrocnemius muscle activity to get an indication of how well you will respond.

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