MAXIMAL INSPIRATORY PRESSURE FOLLOWING ENDURANCE TRAINING AT ALTITUDE

Effects of endurance training on maximal inspiratory pressure and fati gue were evaluated after 5 weeks. Twelve male and 9 female untrained s ubjects were matched in the three groups for sex and maximal oxygen up take (VO2max). Training was performed at 70% VO2 max; 45 min day-1; 5 days week-1 (n = 7); and at the same relative (n = 7) and absolute (n = 7) work loads in a pressure chamber corresponding to 2500 m (560 mmH g). Work load was increased every week to maintain the training heart rate. Maximal inspiratory pressure was measured at the mouth before an d 30, 60 and 120s after maximal exercise. With no significant differen ce between the three groups of subjects, VO2max increased from 2.96 (1 .98-4.47) (median and range for 21 subjects) to 3.33 (2.50-4.72) 1 min -1 (p < 0.001) and ventilation (VE max) from 109 (57-147) to 123 (73-1 48) 1 min-1 (p < 0-001), while maximal heart rate decreased from 193 ( 180-211) to 192 (169-207) beats min-1 (p < 0.01). Maximal inspiratory pressure (87(56-115) mmHg), inspiratory muscle fatigue (18 (-2-43)%, p < 0.001), and arterial oxygen tension during exercise (12.4 (9.9-15.6 ) kPa) were similar before and after training. The results demonstrate that training at simulated altitude at 2500 m does not increase VE ma x or VO2 max above the increases obtained from training at sea level. Furthermore, VE max and VO2 max increased approximately 13% despite un changed maximal inspiratory pressure and inspiratory muscle fatigue. T hese findings indicate that inspiratory muscles do not limit maximal p erformance of short duration in untrained humans.