Relationships of Pulmonary Oxygen Uptake Kinetics with Skeletal Muscle Fatigue Resistance

Abstract. [Purpose] The objective of this study was to determine the validity of pulmonary oxygen uptake ki-netics in assessment of the ability of skeletal muscles to utilize oxygen. [Subjects] We evaluated 12 young, healthy males. [Methods] The subjects completed a series of tests to determine their peak oxygen uptake, pulmonary oxy-gen uptake kinetics at the onset of moderate-intensity treadmill exercise, and the rate of decline in electromyo-graphic (EMG) mean power frequency (MPF) (EMG MPFrate) during one continuous, fatiguing, isometric muscle action of the plantar flexors until exhaustion at approximately 60 % maximum voluntary contraction. We discussed the relationships between pulmonary oxygen uptake kinetics and EMG MPFrate reflecting the ability of skeletal muscles to utilize oxygen and between pulmonary oxygen uptake kinetics and peak oxygen uptake reflecting the ability to deliver oxygen to skeletal muscles. We hypothesized that pulmonary oxygen uptake kinetics may be more highly correlated with EMG MPFrate than peak oxygen uptake. [Results] Pulmonary oxygen uptake kinetics (33.9 ± 5.9 s) were more significantly correlated with peak oxygen uptake (50.6 ± 5.5 mL/kg/min) than EMG MPFrate (−14.7 ± 8.7%/s). [Conclusion] Pulmonary oxygen uptake kinetics is a noninvasive index that is mainly usable for evalua-tion of the ability of cardiovascular system to deliver oxygen to skeletal muscles in healthy young adults with slower pulmonary oxygen uptake kinetics (>20 s)