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Subject-specific Musculoskeletal Model for Studying Bone Strain During Dynamic Motion
Published on: April 11, 2018
Leg and joint stiffness in human hopping.
S Kuitunen1, K Ogiso, P V Komi
1Neuromuscular Research Center, Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä, Finland. sami.kuitunen@hotmail.com
Scandinavian Journal of Medicine & Science in Sports
|December 1, 2011
Summary
Leg and joint stiffness regulation during hopping is primarily controlled by central motor commands, not stretch reflexes. Knee joint stiffness increases with hopping intensity to enhance jumping height.
Area of Science:
- Biomechanics
- Human Movement Science
- Exercise Physiology
Background:
- Understanding how the human body adjusts leg and joint stiffness during locomotion is crucial for optimizing performance and preventing injuries.
- Hopping, a common mode of locomotion, involves complex interactions between muscles, tendons, and joints to manage ground reaction forces and maintain stability.
Purpose of the Study:
- To investigate the regulation of leg and joint stiffness during hopping across different intensity levels.
- To determine the influence of hopping intensity on joint-specific stiffness (ankle and knee) and overall leg stiffness.
- To examine the role of electromyography (EMG) and stretch reflexes in modulating stiffness during hopping.
Main Methods:
- Eight male subjects performed bilateral hopping at varying intensities, defined by peak vertical ground reaction force (GRF).
- Measurements included GRF, hopping kinematics, and EMG activity of selected leg muscles.
- Analysis focused on changes in leg, ankle, and knee joint stiffness, as well as muscle activation patterns and stretch reflex responses.
Main Results:
- Leg and ankle joint stiffness remained constant across different hopping intensities.
- Knee joint stiffness significantly increased with higher hopping intensities (P<0.01).
- Average EMG activity increased in all measured muscles with intensity, but only the vastus lateralis showed a significant increase in stretch reflex EMG (P<0.01).
Conclusions:
- Leg stiffness modulation in hopping is influenced by ankle joint stiffness, while knee joint stiffness regulates jumping performance.
- Hopping stiffness adjustments are primarily driven by central motor commands, with muscle-dependent contributions from stretch reflexes.
- These findings highlight the distinct roles of different joints and neural control mechanisms in regulating hopping mechanics at varying intensities.
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