Effects of endurance training on maximal inspiratory pressure and fatigue were evaluated after 5 weeks. Twelve male and 9 female untrained subjects were matched in the three groups for sex and maximal oxygen uptake (VO2 max). Training was performed at 70% VO2max; 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 mmHg). Work load was increased every week to maintain the training heart rate. Maximal respiratory pressure was measured at the mouth before and 30, 60 and 120 s after maximal exercise. With no significant difference 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 (73-148) 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 max or VO2 max above the increases obtained from training at sea level. Furthermore, VEmax and VO2 max increased approximately 13% despite unchanged maximal inspiratory pressure and inspiratory muscle fatigue.(ABSTRACT TRUNCATED AT 250 WORDS)