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Age does not influence muscle fiber length adaptation to increased excursion
1Department of Health and Performance Sciences, Georgia Institute of Technology, 281 Ferst Dr., Atlanta, GA 30332-0356, USA. thomas.burkholder@hps.gatech.edu
Journal of Applied Physiology (Bethesda, Md. : 1985)
|November 22, 2001
Summary
Adult and young rat muscles adapt similarly to increased excursion, showing a trend for increased fiber length. This suggests dynamic mechanical signals influence muscle fiber length adaptation, not just static muscle length.
Area of Science:
- Muscle Physiology
- Skeletal Muscle Adaptation
Background:
- Muscle fiber length adaptation is age-dependent, with young muscles adding sarcomeres.
- The response of adult muscles to increased excursion is not well understood.
Purpose of the Study:
- To investigate if adult rat muscles exhibit similar sarcomere addition and fiber length adaptation as young muscles.
- To determine the influence of dynamic mechanical signals on muscle fiber length.
Main Methods:
- Transection of the ankle flexor retinaculum in neonatal and adult rats to increase tibialis anterior muscle excursion.
- Measurement of sarcomere number and fiber length after 8 weeks of adaptation.
Main Results:
- Increased muscle moment arm and excursion (30%) in both age groups.
- Reduced muscle cross-sectional area (12%) irrespective of age.
- A trend for increased fiber length (6%) in both neonatal and adult rats, opposing predicted decrease.
Conclusions:
- Adult and young rat muscles respond similarly to increased excursion.
- Dynamic mechanical signals, not just static length, influence muscle fiber length adaptation.
- Sarcomere addition may not be the primary mechanism for fiber length adaptation in this model.