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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
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Residual force depression is affected by muscle length
Atsuki Fukutani1,2, Tadao Isaka3,4
1Faculty of Sport and Health Science, Ritsumeikan University, 1-1-1 Noji-Higashi, Kusatsu, Shiga, 525-8577, Japan. afr15171@fc.ritsumei.ac.jp.
Scientific Reports
|February 19, 2025
Summary
Residual force depression, where active muscle force is reduced after shortening, is greater at longer muscle lengths. This effect is partly due to differences in mechanical work during shortening, but not solely explained by it.
Area of Science:
- Muscle physiology
- Biomechanics
- Cellular mechanics
Background:
- Residual force depression is a phenomenon where active muscle force is reduced after a period of active shortening compared to purely isometric contractions at the same muscle length and activation.
- The underlying mechanisms of residual force depression are not fully understood, and its dependence on muscle length requires further investigation.
Purpose of the Study:
- To investigate whether the magnitude of residual force depression is influenced by the muscle's length.
- To determine the relationship between mechanical work during shortening and residual force depression across different muscle lengths.
Main Methods:
- Experiments were conducted on single-skinned fibers from rabbit psoas muscle (n=8).
- Isometric forces were measured at three average sarcomere lengths (2.1, 2.4, and 2.7 μm).
- Isometric forces after active shortening (from 2.7 to 2.4 μm, and 2.4 to 2.1 μm) were measured to calculate residual force depression at long (2.4 μm) and short (2.1 μm) length conditions.
Main Results:
- The magnitude of residual force depression was significantly greater at the longer muscle length condition (2.4 μm) compared to the shorter condition (2.1 μm) (p=0.046).
- While not statistically significant, the mean force and mechanical work attained during shortening tended to be greater at the longer muscle length (p=0.074).
- Some fibers exhibited substantial differences in residual force depression despite minimal variations in mechanical work, suggesting mechanical work alone does not fully explain the observed muscle length dependency.
Conclusions:
- Residual force depression is dependent on muscle length, being more pronounced at longer lengths.
- Differences in mechanical work during shortening contribute to muscle length-dependent residual force depression, but do not solely account for the phenomenon.
- Further research is needed to elucidate the complex mechanisms underlying residual force depression and its interaction with muscle length.
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