Forearm composition and muscle function in trained and untrained limbs

Abstract

The influence of a period of training, which lasts for several years, on the proportions of muscle, fat and bone present in the human forearm has been investigated by comparing trained and untrained limbs of nine experienced male tennis players. Ten healthy but untrained males of similar age served as a control group. Computed tomography (CT) scans of the forearm were made at intervals along its length to identify fat, muscle and bone and to calculate the volumes occupied by each of these components. Total forearm volume was greater in the dominant limb compared with the contralateral side in both trained (by 135 .+-. 59 cm3, mean .+-. SD, P < 0.001) and untrained subjects (by 41 .+-. 45 cm3, P < 0.02). Forearm muscle volume was also greater in dominant limbs of trained (by 117 .+-. 52 cm3, P < 0.001) and untrained by 35 .+-. 41 cm3, P < 0.025) subjects. Muscle accounted for 75.4 .+-. 2.7% of the total volume in the dominant arm of trained subjects compared with 71.4 .+-. 4.2% in the control group (P < 0.05). There was a greater proportion of muscle (P < 0.05) and a smaller proportion of fat (P < 0.001) in the trained limb compared with the contralateral limb of the same subjects. No differences in proportions of fat, muscle and bone were observed in dominant and non-dominant limbs of the control subjects. Trained subjects were able to exert a greater isometric force with the dominant limb (549 .+-. 76N) than with the non-dominant limb (496 .+-. 48N; P < 0.005). There was no difference in grip strength between the arms of the untrained group (dominant: 516 .+-. 107 N; non-dominant: 491 .+-. 91 N). The ratio of strength of muscle volume was, however, the same in dominant and non-dominant arms of both groups of subjects.