Maximum Blood Lactate Responses Acutely and After Two Weeks of Moderate Altitude Exposure in a Large Multi‐year Study

Abstract

There has been a great deal of controversy associated with the Lactate Paradox since Edwards in 1936 proposed that maximum blood lactate responses are reduced after altitude acclimatization. Conversely, with acute ascent to altitude there are many reports that maximum blood lactate responses are unchanged. To our knowledge, no studies with a large subject pool have looked at maximum blood lactate after acute exposure, acclimatization and upon return to sea level in the same study.PurposeTherefore, the purpose of these studies was to determine the effect of moderate altitude exposure on maximum blood lactate acutely, after acclimatization, and upon return to sea level.MethodsOver the course of a 6‐year period, thirty nine, active subjects (age = 23.3 ± 3.5 yrs, weight = 80.1 ± 17.5 kg, VO2max = 44.9 ± ml/kg/min) completed a graded‐exercise test to exhaustion on a cycle ergometer at sea level (SL1), upon acute exposure to 3400 m (ALT1), two weeks following acclimatization at 3400 m (ALT2), and upon return to sea level (SL2). Workloads were increased every two minutes following a two‐minute warmup until volitional fatigue. A venous blood sample was taken via an in‐dwelling catheter without stasis for subsequent lactate determination. Lactate was measured every 2 minutes during the exercise and then every 2 minutes after for 10 minutes.ResultsMaximum blood lactate was unchanged from SL1 to ALT 1 (11.87 ±2.17 vs. 11.28 ±2.33 mmol/l). However, ALT2 (9.82±1.70 mmol/l ) was significantly lower than both SL1 and ALT1. Maximum blood lactate returned to SL1 values upon return to sea level (SL2 = 11.30±2.77mmol/l).ConclusionsThese data suggest that acute altitude exposure does not result in a reduction in maximum blood lactate. However, after two weeks of acclimatization maximum blood lactate is reduced and returns to pre‐sea level values upon return to sea level.