| The purpose of this study was to compare the kinetics of oxygen uptake in healthy females during arm ergometry exercise in a one-gravity (upright sitting posture) and in a simulated microgravity (-6 deg head-down tilt) condition. Participants performed an incremental arm ergometry test to assess peak oxygen uptake. Participants were then randomly ordered into one of the two gravity conditions. In each gravity condition, participants performed a constant-load arm ergometry test at 65% of their peak oxygen uptake for 30 min. oxygen uptake, heart rate, blood pressure, and blood lactate were monitored during exercise.;A random regression effects model was developed to analyze the kinetics of oxygen uptake for gravity conditions. Hypotheses testing for oxygen uptake during the 30-min constant load arm ergometry exercise involved a comparison of mean profile curves for three intervals of time (Interval 1, 0 to 6 min; Interval 2, 8 to 16 min; and Interval 3, 18 to 30 min of exercise) for the gravity conditions. Blood lactate was analyzed using a heterogeneous, variance component model. Significance was established at a probability ≤.05.;A natural slow component of oxygen uptake was found in both gravity conditions. The slow component of oxygen uptake in the one-gravity position exceeded that of simulated microgravity for Intervals 2 and 3.;Lactate production patterns in the gravity conditions indicated that between Minutes 6 and 30 of exercise there was a significant difference in the mean change in lactate production between the two gravity conditions with onegravity condition dominating over simulated microgravity.;It was concluded that the slow component of oxygen uptake was influenced by gravity condition with the one-gravity condition eliciting greater oxygen uptake over time than the simulated microgravity condition. A natural slow component of oxygen uptake developed over time during the 30 min constant-load arm ergometry exercise in both gravity conditions, with the size of the slow component being slightly larger in the one-gravity condition. |
