EXERCISE TRAINING IN CHRONIC HYPOXIA HAS NO EFFECT ON VENTILATORY MUSCLE FUNCTION IN HUMANS

At the highest altitude, aerobic work is limited by environmental oxyg en availability. We therefore reasoned that the hyperpnea associated w ith endurance training at altitude should provide a strong stimulus fo r adaptation of the ventilatory muscles. We measured peak inspiratory muscle pressure-flow characteristics (inspiring through graded resisto rs) and maximum sustainable ventilation capacity in ten permanent resi dents of La Paz, Bolivia (3600 m) prior to and immediately following 6 weeks of incremental endurance training. Additionally, eight local re sidents did no training and functioned as controls for the capacity te st. While V(O2)max measured in hypoxia increased by 19% (Favier et al. , 1995b. J. Appl Physiol. 78, 2286-2393), none of the tested ventilato ry variables showed significant changes. The values for the group mean slopes of maximum inspiratory pressure-flow pairs (-10.5 vs. -9.8 cm H2O.sec.L-1, P = 0.301; before versus after training, respectively), m aximum inspiratory pressure (112.1 +/- 8.9 vs. 106.9 +/- 8.6 cmH(2)O, P = 0.163), peak inspiratory flow (9.8 +/- 0.41 vs. 10.2 +/- 0.55 L.se c(-1), P = 0.172) and the maximum volitional volume in 12 sec (43.9 +/ - 2.4 vs. 45.6 +/- 2.4 L in 12 sec, P = 0.133) were unchanged with exe rcise training. Likewise, maximal sustainable minute volume was not di fferent between post-training and control subjects (177.4 +/- 7.9 vs. 165.4 +/- 8.4 L.min(-1), P = 0.141). These data support the concept th at endurance training fails to elicit functional adaptations in ventil atory muscles in humans, even when exercise is done in hypoxia. (C) 19 98 Elsevier Science B.V. All rights reserved.