Living and training in moderate hypoxia does not improve Vo(2max) more than living and training in normoxia

The objective of these experiments was to determine whether living and trai ning in moderate hypoxia (MHx) confers an advantage on maximal normoxic exe rcise capacity compared with living and training in normoxia. Rats were acc limatized to and trained in MHx [inspired PO2 (PIO2) = 110 Torr] for 10 wk (HTH). Rats living in normoxia trained under normoxic conditions (NTN) at t he same absolute work rate: 30 m/min on a 10 degrees incline, 1 h/day, 5 da ys/wk. At the end of training, rats exercised maximally in normoxia. Traini ng increased maximal O-2 consumption ((V)over dot O-2 max) in NTN and HTH a bove normoxic (NS) and hypoxic (HS) sedentary controls. However, (V)over do t O-2 max and O-2 transport variables were not significantly different betw een NTN and HTH: (V)over dot O-2 max 86.6 +/- 1.5 vs. 86.8 +/- 1.1 ml.min(- 1).kg(-1); maximal cardiac output 456 +/- 7 vs. 443 +/- 12 ml.min(-1).kg(-1 ); tissue blood O-2 delivery (cardiac output x arterial O-2 content) 95 +/- 2 vs. 96 +/- 2 ml.min(-1).kg(-1); and O-2 extraction ratio (arteriovenous O-2 content difference/arterial O-2 content) 0.91 +/- 0.01 vs. 0.90 +/- 0.0 1. Mean pulmonary arterial pressure (Ppa, mmHg) was significantly higher in HS vs. NS (P < 0.05) at rest (24.5 <plus/minus> 0.8 vs. 18.1 +/- 0.8) and during maximal exercise (32.0 +/- 0.9 vs. 23.8 +/- 0.6). Training in MHx si gnificantly attenuated the degree of pulmonary hypertension, with Ppa being significantly lower at rest (19.3 +/- 0.8) and during maximal exercise (29 .2 +/- 0.5) in HTH vs. HS. These data indicate that, despite maintaining eq ual absolute training intensity levels, acclimatization to and training in MHx does not confer significant advantages over normoxic training. On the o ther hand, the pulmonary hypertension associated with acclimatization to hy poxia is reduced with hypoxic exercise training.