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Sex-based differences in skeletal muscle function and morphology with short-term limb immobilization
Nobuo Yasuda1, Elisa I Glover, Stuart M Phillips
1Dept. of Kinesiology, McMaster Univ., Hamilton, Ontario, Canada.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|April 30, 2005
Summary
Women experience greater strength loss after leg immobilization than men, despite similar muscle size reduction. This study highlights sex-specific differences in muscle function recovery following immobilization.
Area of Science:
- Exercise Physiology
- Muscle Biology
- Human Physiology
Background:
- Unilateral leg immobilization is a common model to study muscle atrophy.
- Understanding sex-specific responses to immobilization is crucial for targeted rehabilitation.
- Previous research has not fully elucidated the differential effects of immobilization on muscle strength and morphology between men and women.
Purpose of the Study:
- To investigate the effects of short-term unilateral leg immobilization on muscle function and morphology in men and women.
- To compare the sex-specific responses in knee extensor strength, muscle size, and fiber type composition after 14 days of immobilization.
Main Methods:
- 14-day unilateral leg immobilization using a knee brace or crutches in healthy men and women.
- Assessment of isometric and isokinetic knee extensor peak torque at multiple time points.
- Magnetic resonance imaging (MRI) for quadriceps femoris cross-sectional area and dual-energy X-ray absorptiometry (DXA) for leg lean mass.
- Muscle biopsies for myosin ATPase and myosin heavy chain analysis.
Main Results:
- Women exhibited significantly greater decreases in specific strength (N/cm2) for isometric and slow-concentric contractions compared to men.
- No significant sex-specific differences were observed in the reduction of quadriceps femoris cross-sectional area or leg lean mass.
- Muscle fiber areas (Type I, IIa, IIx) decreased similarly between sexes, with no observed fiber-type transformations.
Conclusions:
- Immobilization leads to greater knee extensor muscle strength loss in women compared to men, despite similar muscle atrophy at both myofiber and whole muscle levels.
- The findings suggest sex-specific differences in neuromuscular adaptations or recovery mechanisms following immobilization.
- An effective and safe knee immobilization protocol was established, demonstrating significant reductions in quadriceps muscle strength and size.