Effects of oxygen fraction in inspired air on force production and electromyogram activity during ergometer rowing.

Six male rowers rowed maximally for 2500 m in ergometer tests during normoxia (fractional concentration of oxygen in inspired air, F(I)O2 0.209), in hyperoxia (F(I)O2 0.622) and in hypoxia (F(I)O2 0.158) in a randomized single-blind fashion. Oxygen consumption (VO2), force production of strokes as well as integrated electromyographs (iEMG) and mean power frequency (MPF) from seven muscles were measured in 500-m intervals. The iEMG signals from individual muscles were summed to represent overall electrical activity of these muscles (sum-iEMG). Maximal force of a stroke (Fmax) decreased from the 100% pre-exercise maximal value to 67 (SD 12)%, 63 (SD 15)% and 76 (SD 13)% (P < 0.05 to normoxia, ANOVA) and impulse to 78 (SD 4)%, 75 (SD 14)% and 84 (SD 7)% (P < 0.05) in normoxia, hypoxia and hyperoxia, respectively. A strong correlation between Fmax and VO2 was found in normoxia but not in hypoxia and hyperoxia. The mean sum-iEMG tended to be lower (P < 0.05) in hypoxia than in normoxia but hyperoxia had no significant effect on it. In general, F(I)O2 did not affect MPF of individual muscles. In conclusion, it was found that force output during ergometer rowing was impaired during hypoxia and improved during hyperoxia when compared with normoxia. Moreover, the changes in force output were only partly accompanied by changes in muscle electrical activity as sum-iEMG was affected by hypoxic but not by hyperoxic gas. The lack of a significant correlation between Fmax and VO2 during hypoxia and hyperoxia may suggest a partial uncoupling of these processes and the existence of other limiting factors in addition to VO2.

Effects of oxygen fraction in inspired air on rowing performance.

The present study examined the effect of oxygen fraction in inspired air (FIO2) on exercise performance and maximum oxygen consumption (VO2max). Six national level male rowers exercised three 2500-m all-out tests on a Concept II rowing ergometer. Each subject performed one test in normoxia (FIO2 20.9%), one in simulated hyperoxia (FIO2 62.2%) and one in simulated hypoxia (FIO2 15.8%) in a randomized single-blind fashion. The mean final rowing time was 2.3 +/- 0.9% (P < 0.01; 95% CI 1.4-3.2) shorter in hyperoxia and 5.3 +/- 1.8% (P < 0.01; 95% CI 3.1-7.5) longer in hypoxia when compared with normoxia. The effect of FIO2 on VO2max exceeded its effect on exercise performance as VO2max was 11.1 +/- 5.7% greater (P < 0.01; 95% CI 5.1-17.1) in hyperoxia and 15.5 +/- 3.2% smaller in hypoxia (P < 0.01; 95% CI 12.2-19.0) than in normoxia. Blood lactate concentration and O2 consumption per power unit (ml O2.W-1) failed to indicate statistically significant differences in anaerobic metabolism between normoxia and the other two conditions. These data suggest that there are other parameters besides those of energy metabolism that affect exercise performance as FIO2 is modified. These possible mechanisms are discussed in this paper.