Abstract des Autors

The cross-sectional areas (CSA) of fat, muscle and bone tissues of the limb as well as maximal voluntary isokinetic strength were measured in untrained men and women (18-25 y). Anatomical CSA of these tissues were determined by ultrasound on the upper arm and thigh. Isokinetic strength of elbow and knee extensor and flexor muscles were measured by an isokinetic dynamometer (Cybex II) at 1.05 rad/s. Women had significantly larger fat CSA and smaller bone and muscle CSA than men in both upper arm and thigh. Among tissue CSA, the largest difference between women and men was found in fat CSA regardless of the measurement sites. The sex differences in bone and muscle CSA were found largely in the upper arm compared to the thigh, even when expressed per unit second power of the limb length. Regression analyses of the data for respective samples for men and women showed significant correlations between CSA and strength in all muscle groups except for the elbow extensors of the men and the elbow flexors of the women. No significant difference between sexes was observed when strength was expressed per unit of muscle CSA (F/CSA) for the elbow flexors and extensors. However, men showed significantly higher F/CSA than women for knee flexors and extensors. These results would indicate that, although the difference between sexes in muscle CSA is smaller in the thigh than in the upper arm, differences in the ability to develop dynamic strength proportional to the CSA appeared mainly in the thigh muscles compared to upper arm muscles.