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Mechanical work as predictor of force enhancement and force depression
Natalia Kosterina1, Håkan Westerblad, Anders Eriksson
1KTH Mechanics, Royal Institute of Technology, Osquars backe 18, SE-100 44 Stockholm, Sweden.
Journal of Biomechanics
|June 3, 2009
Summary
Muscle force depends on its previous activity, not just its current length. Mechanical work done on or by the muscle during shortening or stretch directly influences this history-dependent force modification.
Area of Science:
- Muscle physiology
- Biomechanics
- Skeletal muscle research
Background:
- Muscle force generation is influenced by factors beyond immediate muscle length and velocity.
- Muscle contraction history significantly impacts steady-state force production.
Purpose of the Study:
- To investigate history-dependent modifications in muscle force.
- To identify parameters influencing these force changes, specifically mechanical work.
Main Methods:
- Isolated mouse extensor digitorum longus and soleus muscles were used.
- Muscles underwent pre-stimulation, followed by controlled stretch/shortening episodes.
- Active and passive force changes were recorded during isometric contractions post-perturbation.
Main Results:
- A negative linear correlation was observed between force modification and mechanical work (shortening/stretch).
- This relationship was consistent across both shortening and stretching conditions.
- Passive force components also showed modifications following stimulation and mechanical work.
Conclusions:
- Isometric muscle force is determined by preceding mechanical work, not solely by current length.
- The steady-state force can be described as an asymptotic force influenced by mechanical work.
- Muscle's mechanical history is a critical determinant of its force-generating capacity.
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