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Isometric and Eccentric Force Generation Assessment of Skeletal Muscles Isolated from Murine Models of Muscular Dystrophies
Published on: January 31, 2013
Changes in human skeletal muscle length during stimulated eccentric muscle actions
Stephen J Brown1, Alan Donnelly
1Division of Exercise and Sport Science, Institute of Food, Nutrition and Human Health, Massey University Albany, Private Bag 102-904, Auckland, New Zealand. s.j.brown@massey.ac.nz
The Journal of Physiological Sciences : JPS
|November 17, 2010
Summary
Eccentric exercise alters skeletal muscle
Area of Science:
- Exercise Physiology
- Skeletal Muscle Physiology
- Biomechanics
Background:
- Eccentric exercise, involving muscle lengthening under tension, is known to alter the skeletal muscle length-tension relationship.
- However, it remains unclear whether these alterations occur dynamically during the eccentric exercise bout itself.
Purpose of the Study:
- To investigate if the muscle length-tension relationship shifts during eccentric exercise.
- To quantify angle-specific force changes and the shift in optimal muscle length during eccentric contractions.
Main Methods:
- Seventy eccentric actions of knee extensors were performed at 100°/s from full extension to flexion.
- Superimposed electrical stimulation was used to ensure maximal muscle activation.
- Angle-specific eccentric force was measured throughout the range of motion.
Main Results:
- Force decreased non-uniformly across all muscle lengths, with greater reductions at shorter lengths (e.g., 41% at 130° vs. 25% at 70°).
- Peak force decreased by 21% after the exercise bout.
- The position of peak force production shifted 10° towards shorter muscle lengths (from 100° to 90°).
Conclusions:
- The muscle length-tension relationship shifts during eccentric exercise, characterized by a rightward shift in the optimal length.
- Greater force loss at shorter muscle lengths suggests sarcomere over-stretching occurs during eccentric contractions.
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