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Publication AbstractsOxygen Uptake Response during Maximal Cycling in Hyperoxia, Normoxia and HypoxiaJuha E. Peltonen, LitL, M.Sc., Heikki O. Tikkanen, M.D., Jarmo J. Ritola, M.Sc., Markku Ahotupa, Ph.D., and Heikki K. Rusko, Ph.D.Aviat Space Environ Med 2001; 72:904-11 AbstractBackground: Oxygen uptake (V(dot)O2) on-kinetics is decelerated in acute hypoxia and accelerated in hyperoxia in comparison with normoxia during submaximal exercise. However, the effects of fraction of oxygen in inspired air (FIO2) on V(dot)O2 kinetics during maximal exercise are unknown. Hypothesis: The effects of FIO2 on V(dot)O2 on-kinetics during maximal exercise are similar to submaximal exercise. Methods: There were 11 endurance athletes who were studied during maximal 7-min cycle ergometer exercise in hyperoxia (FIO2 0.325), hypoxia (FIO2 0.166) and normoxia (FIO2 0.209). The individual V(dot)O2 data were fit to a curve by using a three exponential model. Results: In hypoxia, V(dot)O2 on-response amplitude during Phase 2 (~ 20-100 s from the beginning of exercise) was lower (p < 0.05) when compared with hyperoxia; time constant of V(dot)O2 Phase 3 (beyond ~ 100 s after beginning of exercise) was shorter (p < 0.05) when compared with hyperoxia; and mean response time (MRT, O-63%) for V(dot)O2peak was shorter (p < 0.05) when compared with normoxia and hyperoxia. V(dot)O2peak was higher in hyperoxia (4.80 ± 0.48 L · min-1, p < 0.05) and lower in hypoxia (4.03 ± 0.46 L · min-1, p < 0.05) than in normoxia (4.36 ± 0.44 L · min-1). Conclusions: Moderate hypoxia or hyperoxia do not affect V(dot)O2 time constants at the onset of maximal exercise. However, MRT for V(dot)O2peak is shortened in hypoxia. It is suggested that the differences in V(dot)O2peak and power output during the latter half of the test and the point that FIO2 was modified only moderately might explain most of the discrepancy with the previous studies.Keywords: curve fitting; V(dot)O2peak, hemoglobin O2 saturation, blood lactate, oxidative stress. Information on subscribing, and on obtaining copies of an article or of an entire issue. Table of Contents for Volume 72, Number 10 of the ASME journal.
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