Comparison of muscle cross-sectional area and strength between untrained women and men

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 (n = 27) and women (n = 26) aged 18-25 years. Anatomical CSA of the three tissues were determined by ultrasound on the upper arm and thigh. The isokinetic strength of the elbow and knee extensor and flexor muscles were measured by an isokinetic dynamometer (Cybex II) at 1.05 rad.s-1. The women had significantly (P < 0.001) larger fat CSA and smaller bone and muscle CSA than the men in both the upper arm and thigh. Among tissue CSA, the largest difference between the 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 the men and women showed significant correlations (r = 0.411-0.707, P < 0.05-P < 0.001) between CSA and strength in all muscle groups except for the elbow extensors of the men (r = 0.328, P > 0.05) and the elbow flexors of the women (r = 0.388, P > 0.05). No significant difference between sexes was observed when strength was expressed per unit of muscle CSA (F.CSA-1) for the elbow flexors and extensors. However, the men showed significantly higher F.CSA-1 than the women for the knee flexors and extensors (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)