Gooding, B., Cole, J., Hicks, D., Clark, M., & Davis, J. E. (2013). Effects of moderate altitude on oxygen debt, oxygen deficit, and the onset of blood lactate during exercise. Medicine & Science in Sports & Exercise, 45(5), Supplement abstract number 2818.

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This study examined the effects of moderate altitude on oxygen debt, oxygen deficit, and the onset of blood lactate accumulation during exercise to exhaustion. Ss (N = 6) underwent graded-exercise tests to exhaustion on a cycle ergometer at sea-level, upon acute exposure to 3,400 m, two weeks of acclimatization at 3,400 m, and upon return to sea-level. In the testing protocol, workloads increased every two minutes following a two-minute warm-up until volitional fatigue. For each test, maximal oxygen consumption, maximum blood lactate levels, onset of blood lactate accumulation, and the oxygen deficit were measured. Oxygen deficit was compared to the oxygen debt. Breath-by-breath oxygen consumption values were measured before each exercise, during each workload, and after the exercise to calculate the oxygen deficit and debt. Venous blood lactate measurements were taken at each workload and for six minutes after the exercise.

Upon acute exposure to 3,400 m, VO2max and maximum blood lactate levels decreased significantly in comparison to sea-level. VO2max returned to sea-level values within two weeks of altitude acclimatization, but maximum blood lactate levels remained depressed throughout the two-week period. Onset of blood lactate accumulation did not differ between sea-level and acute exposure to 3,400 m or after two weeks of acclimatization. Oxygen deficit and debt decreased from sea-level to acute exposure to altitude and returned to sea-level values upon returning to sea-level.

Implication. While the onset of blood lactate accumulation was not affected by either acute or chronic exposure, maximum blood lactate levels decreased at the same times. Oxygen debt and deficit were depressed at moderate altitude as was VO2max . It seems that moderate altitude does not influence the rate of lactate accumulation at low exercise levels, but does during maximal exercise. In contrast, oxygen adjustments to graded exercise and maximum aerobic capacity were both influenced by moderate altitude exposure.

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