Abstract

Aim of the present study was to test the hypothesis that the net maximal blood lactate accumulation ((La)max) during heavy exercise in lowlanders acclimatized to chronic hypoxia may be limited by the reduced bicarbonate stores. Six men performed supramaximal exercise until voluntary exhaustion at sea level (204+/-54 W) and after sojourning for 1 mo at 5,050 m (175+/-23 W), without (C) and with (B) oral sodium-bicarbonate loading (0.3 g/kg body wt). Exhaustion time, arterial blood lactate concentration, arterial pH (pHa), arterial PCO2, and intramuscular pH were measured at rest and after exercise. At sea level, exhaustion time increased from 6.5+/-2.8 min in C to 7.5+/-2.7 min in B. At altitude, exhaustion times were similar to the sea level C values and the same in C and B. At sea level, resting pHa increased from 7.41+/-0.02 in C to 7.46+/-0.03 in B; the corresponding values at altitude were 7.46+/-0.04 and 7.55+/-0.03. Postexercise pHa at sea level was 7.22+/-0.02 in C and 7.25+/-0.08 in B. After exercise at altitude, pHa was 7.32+/-0.04 and 7.44+/-0.03 in C and B, respectively. (La)max increased from 12.86+/-1.45 mM in C to 16.63+/-1.76 mM in B at sea level and from 6.85+/-1.40 mM in C to 7.95+/-1.74 mM in B at altitude. Postexercise intramuscular pH was significantly higher at altitude than at sea level, independent of bicarbonate loading. It is concluded that the decreased buffer capacitiy accompanying high-altitude acclimatization is not responsible for the observed decrease in (La)max in acclimatized lowlanders. Verf.-Ref.