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Changes in muscle activity in response to different impact forces affect soft tissue compartment mechanical
Katherine A Boyer1, Benno M Nigg
1Division of Biomechanical Engineering, Department of Mechanical Engineering, 219 Durand Bldg., 496 Lomita Mall, Stanford University, Stanford, CA 94305-4038, USA. Kboyer@stanford.edu
Journal of Biomechanical Engineering
|July 28, 2007
Summary
Muscle tuning helps minimize soft tissue vibrations during walking and running impacts. Changes in leg muscle activity patterns adapt to impact conditions, reducing vibration transmission.
Area of Science:
- Biomechanics
- Human Physiology
- Musculoskeletal System
Background:
- Electromyographic (EMG) activity plays a role in leg positioning, joint stiffness, and controlling soft tissue vibrations during locomotion.
- Muscle tuning is a proposed mechanism where altered muscle activity patterns minimize soft tissue vibrations when impact frequencies match natural frequencies.
Purpose of the Study:
- To investigate if changes in muscle activation patterns alter acceleration transmissibility to soft tissue compartments under different impact conditions.
- To test the hypothesis that muscle activation changes modify the mechanical properties of soft tissues, thereby influencing vibration transmission.
Main Methods:
- A pendulum apparatus delivered controlled impacts to the heel of shod male participants.
- Quantified wall reaction forces, EMG activity of leg muscles, and accelerations of soft tissue compartments and shoe heel cups.
- Calculated acceleration transmissibility to soft tissue compartments for various subject/compartment/shoe combinations.
Main Results:
- Changes in damping properties of soft tissue compartments correlated with alterations in EMG intensity and/or mean frequency of related muscles.
- These correlations were observed in response to modified impact interface conditions.
- Demonstrated a relationship between muscle activation changes and soft tissue compartment damping.
Conclusions:
- Results support the muscle tuning hypothesis.
- Muscle activity changes in response to impact variations may serve to minimize soft tissue compartment vibrations initiated at heel-strike.
- This suggests a protective role for muscle tuning in locomotion.
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