VII. Maximal Muscular Power Before and After Exposure to Chronic Hypoxia

Abstract

The maximal muscular power (both instantaneous, ẇ̄, and average, ẇ̄) and the cross-sectional area of the left thigh (CSA) were measured on six subjects before (B) and after (A) prolonged exposure to high altitude (above 5000 m asl). ẇ̄ and ẇ̄ were determined during a standing high jump off both feet on a force platform, and CSA by computed tomography. It was observed that: (1) in B, body weight (BW = 74.1 ± 5.8 kg, ẇ̄ = 3330 ± 460 W (44.8 ± 3.4 W·kg^-1). ẇ̄ 1795 ± 395 W (24.6 ± 4.3 W·kg^-1), and CSA = 184.5 ± 23.1 cm²; 2) in A, BW = 70.4 + 6.6 kg, ẇ̄ = 3005 ± 472 W (42.5 ± 3.6 W·kg^-1), w = 1531 ± 267 W (21.9 ± 3.1 W-kg^-1), and CSA = 163.5 ± 23.1 cm². Thus, ẇ̄ and ẇ̄ were decreased both in absolute terms (-9.8% and -14.7%, respectively) and per unit BW (-5.1% and -11.0%). However, because of the concomitant decrease in CSA, when expressed per unit cross-sectional area of the muscle, ẇ̄ (9.04 ± 0.71 and 9.20 ± 0.72 W±cm²) and ẇ̄ (4.87 ± 0.81 and 4.70 ± 0.67 W/cm²) were unchanged. The intrinsic capacity of the muscle to generate explosive power is therefore preserved in A. It is concluded that the decrease in ẇ̄ and ẇ̄ after high-altitude exposure depends only on a net loss of muscle mass.

Key words

maximal power - muscle mass - thigh cross-sectional area - anaerobic alactic metabolism