The effect of inspired oxygen fraction on peak oxygen uptake during arm exercise.

It has been shown that peak oxygen uptake (O(2)peak) during leg exercise is enhanced by an increased inspiratory oxygen fraction ( FiO(2)), indicating that oxygen supply is the limiting factor. Whether oxygen supply is a limiting factor in arm exercise performance is unknown. The purpose of this study, therefore, was to examine the effect of different levels of FiO(2 )on O(2)peak during arm exercise in healthy individuals. Nine men successfully performed three incremental arm-cranking exercise tests with FiO(2)15%, FiO(2)21% and FiO(2)50% applied in counterbalanced order. A significant FiO(2 )dependency was observed for O(2)peak ( p=0.02) and power output ( p=0.03) and post hoc tests revealed a significant difference in O(2)peak between 15 and 50% FiO(2 )( p=0.02), but not between 15 and 21% FiO(2), and 21 and 50% FiO(2). The results of this study show that O(2)peak is enhanced with increasing FiO(2), and suggest that O(2)peak during arm exercise is limited by oxygen supply rather than by the metabolic machinery within the muscle itself.