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Sex difference in force generation capacity during repeated maximal knee extensions
H Kanehisa1, H Okuyama, S Ikegawa
1Faculty of Education, Toyama University, Japan.
Summary
Men generate more quadriceps force than women, even when accounting for muscle size. However, women exhibit greater force decline relative to their muscle size during repeated maximal knee extensions.
Area of Science:
- Exercise Physiology
- Muscle Physiology
- Biomechanics
Background:
- Muscle strength and endurance vary between sexes.
- Understanding sex-based differences in muscle force generation and fatigue is crucial for exercise science and rehabilitation.
Purpose of the Study:
- To compare the force generation capacity and fatigue resistance of the quadriceps femoris muscle between untrained young men and women.
- To investigate the relationship between quadriceps cross-sectional area (CSA) and maximal voluntary contraction (MVC) force and fatigue.
Main Methods:
- Fifty repeated maximal knee extensions at a constant velocity (3.14 rad.s-1) were performed by 36 women and 27 men (18-25 years).
- Quadriceps femoris muscle cross-sectional area (CSA) was measured using B-mode ultrasound.
- Force output (F), percentage of decline (%D), and force per unit CSA (F.CSA-1) were calculated.
Main Results:
- Men exhibited significantly higher absolute force output (F) than women across all repetitions.
- Quadriceps CSA was significantly correlated with force output in both sexes (r = 0.552-0.872 for men, r = 0.609-0.857 for women).
- Despite similar average %D, women showed significantly higher %D than men when normalized to initial force per CSA, indicating greater relative fatigue.
Conclusions:
- Quadriceps femoris muscle CSA is a significant determinant of force generation capacity in both young men and women.
- Men produce greater absolute force, but women experience greater relative fatigue during repeated maximal contractions, even when accounting for muscle size differences.