Effects of training at simulated high altitude on exercise at sea level

Nine healthy men trained one leg under normobaric (N) conditions (N-leg), the other leg under hypobaric (H; 572 mmHg) conditions (H-leg) each one 30 min, 3–4 times per week for 4 weeks at 65% of the one-legged maximal work load that could be performed for 2 min ( W _max). They performed one-legged exercise tests to fatigue before and after the training period under N conditions at a load corresponding to 80% of one-legged W _max. Muscle biopsies were taken before training from one leg and after training both from the N-leg and the H-leg at rest and after 15-min exercise and analysed for high-energy phosphates and glycogen and their degradation products. Training under N as well as under H conditions improved local energy balance in the leg (less lactate and inosine monophosphate accumulation). However, a discrepancy was found between the previously demonstrated greater increase in local oxidative potential in the H-leg than in the N-leg and the local energy balance during submaximal exercise, which improved less in the H-leg than in the N-leg (lower energy charge and higher adenosine monophosphate content). Despite less improved local energy balance after 15 min of exercise, the time to fatigue was somewhat longer in the H-leg.