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Experimental Methods to Study Human Postural Control
Published on: September 11, 2019
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Soleus Muscle Stiffness is Regulated by Scaled Activation to Manage Unpredictable and Predictable Walking
Sebastian Bohm1,2, Morteza Ghasemi3,4, Christos Theodorakis3,4
1Department of Training and Movement Sciences, Humboldt-Universität zu Berlin, Berlin, Germany. sebastian.bohm@hu-berlin.de.
Annals of Biomedical Engineering
|December 13, 2025
Summary
Leg muscles absorb energy during gait perturbations to maintain stability. This study reveals how muscle activation and tendon decoupling manage this energy, optimizing muscle-tendon unit function for stability during unexpected drops and obstacles.
Area of Science:
- Biomechanics
- Human Movement Science
- Musculoskeletal Physiology
Background:
- Gait perturbations challenge the body's center of mass (CoM) energy management.
- Leg muscles must absorb this energy reactively to maintain stability.
- Anticipation and experience can modify muscle responses to improve perturbation handling.
Purpose of the Study:
- Investigate the interaction between muscle activation, muscle-tendon unit (MTU) decoupling, and contractile conditions.
- Understand CoM energy management during gait challenges.
- Examine responses to unpredictable and adapted drop perturbations, and hole negotiation.
Main Methods:
- Measured kinematics, electromyographic activity (EMG), soleus fascicle length, and CoM energy.
- Assessed soleus force-length and force-velocity relationships.
- Compared unperturbed walking with unpredictable perturbations, adapted perturbations, and hole negotiation.
Main Results:
- CoM energy absorption occurred during perturbations and hole negotiation.
- Unpredictable perturbations showed rapid EMG increase and near-isometric fascicle behavior despite MTU lengthening.
- Adapted perturbations involved initial isometric contraction followed by active fascicle lengthening; hole negotiation showed fascicle lengthening with low EMG.
Conclusions:
- Muscle stiffness is regulated by scaled activation, tuning muscle and tendon contributions to MTU length changes (tendon decoupling).
- This regulation optimizes fascicle force-length-velocity potentials and tendon energy buffering.
- Findings explain mechanisms for stability during drop-like perturbations and hole negotiation.
Keywords:
Motor adaptation and learningMotor controlMuscle–tendon interactionUneven terrainUnsteady locomotionMore Related Videos
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