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|Title:||Gender Differences in Strength and Muscle Fiber Characteristics|
|Advisor:||MacDougall, J. D.|
|Abstract:||A gender difference in absolute muscle strength is well documented. The extent to which quantitative (fiber area and number) and qualitative (specific tension) differences in muscle contribute to this is not well understood. The purpose of this study was to examine a variety of muscle characteristics in the biceps brachii and vastus lateralis in a sample of males (n=8) and females (n=8) with a wide range of training histories. Measurements included motor unit number, size and activation, and voluntary strength of the elbow flexors and knee extensors. Fiber characteristics were determined from needle biopsies and muscle areas by computerized tomographical scanning. Females were approximately 52% and 66% as strong as the males in the upper and lower body respectively. A significant (p ≤ .05) correlation was found between strength and muscle cross-sectional area. Females had 45, 41, 30 and 25% smaller muscle cross-sectional areas for the biceps brachii, total elbow flexors, vastus lateralis and total knee extensors respectively (p ≤ .01). No significant gender difference was found in the strength to cross-sectional area ratio for elbow flexion and knee extension. Males had significantly larger type I fiber areas (4597 vs. 3483 um² ) and mean fiber areas (6632 vs. 3963 um² ) than females in biceps brachii (p ≤ .05) and significantly larger type II fiber areas (7700 vs. 4040 um²) and mean fiber areas (7070 vs. 4290 um²) in the vastus lateralis (p ≤ .05). The difference in type II fiber area in the biceps brachii was not statistically significant despite the fact that these fibers were almost twice as large in the males as in the females (8207 vs. 4306 um²). No significant gender difference was found in biceps fiber number (180,620 vs. 156,872) or muscle area to fiber area ratio in the vastus lateralis (451,468 vs. 465,007). No significant gender differences were found in any of the motor unit characteristics. The results indicate that the primary determinant of the greater muscle strength of males is their larger mean fiber areas which results in greater muscle cross-sectional areas.|
|Appears in Collections:||Digitized Open Access Dissertations and Theses|
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