Decreased exercise blood lactate concentrations after respiratory endurance training in humans

For many years, it was believed that ventilation does not limit performance in healthy humans. Recently, however, it has been shown that inspiratory m uscles can become fatigued during intense endurance exercise and decrease t heir exercise performance. Therefore, it is not surprising that respiratory endurance training can prolong intense constant-intensity cycling exercise . To investigate the effects of respiratory endurance training on blood lac tate concentration and oxygen consumption ((V) over dot O-2) during exercis e and their relationship to performance, 20 healthy, active subjects underw ent 30 min of voluntary, isocapnic hyperpnoea 5 days a week, for 4 weeks. R espiratory endurance tests, as well as incremental and constant-intensity e xercise tests on a cycle ergometer, were performed before and after the 4-w eek period. Respiratory endurance increased from 4.6 (SD 2.5) to 29.1 (SD 4 .0) min (P < 0.001) and cycling endurance time was prolonged from 20.9 (SD 5.5) to 26.6 (SD 11.8) min (P < 0.01) after respiratory training. The (V) o ver dot O-2 did not change at any exercise intensity whereas blood lactate concentration was lower at the end of the incremental [10.4 (SD 2.1) vs 8.8 (SD 1.9) mmol . l(-1) P < 0.001] as well as at the end of the endurance ex ercise [10.4(SD 3.6) vs 9.6 (SD 2.7) mmol . l(-1) P < 0.01] test after resp iratory training. We speculate that the reduction in blood lactate concentr ation was most likely caused by an improved lactate uptake by the trained r espiratory muscles. However, reduced exercise blood lactate concentrations per se are unlikely to explain the improved cycling performance after respi ratory endurance training.