Muscle strength and cross-sectional area in man: a comparison of strength-trained and untrained subjects.

This study has examined muscle strength and cross-sectional area in a group of 35 healthy untrained male subjects and 8 subjects who had been engaged in a strenuous weight-training programme. The maximum voluntary knee extension force which could be produced by the untrained subjects was 742 +/- 100 N (mean +/- SD). The trained subjects could produce a significantly (p less than 0.001) greater force (992 +/- 162 N). Cross-sectional area of the knee-extensor muscle group was 81.6 +/- 11.8 cm2 in the untrained subjects and 104.1 +/- 12.3 cm2 in the trained subjects (p less than 0.001). In the untrained subjects, a significant correlation existed between strength and muscle cross-sectional area (r = 0.56, p less than 0.001). In the same group of subjects, there was a significant inverse relationship between muscle cross-sectional area and the ratio of strength to cross-sectional area (r = 0.55, p less than 0.001). The mean ratio of strength to cross-sectional area was 9.20 +/- 1.29 for the untrained group whereas for the trained group this ratio was 9.53 +/- 1.01. It is suggested that the inverse relationship between strength per unit cross-sectional area and cross-sectional area results in part from an increased angle of pennation in the larger muscles.