Short-term reliability of oxygen uptake on-kinetics in apparently healthy subjects.

Purpose: The analysis of oxygen (O2) uptake on-kinetics at the onset of aerobic exercise has been shown to be reflective of cardiovascular and skeletal muscle health in a number of previous investigations. The purpose of the present investigation is to assess the short-term reliability of O2 uptake on-kinetics in a group of apparently healthy individuals.

Methods: Forty apparently healthy subjects participated in 3 consecutive treadmill exercise sessions on 3 consecutive days. During each session, O2 uptake was collected at rest for 2 minutes and during ambulation at 2.2 miles per hour and a 6% grade for 6 minutes. The time constant (TC) for the O2 uptake response was calculated for each of the 3 sessions using the equation: O2(t) = O2(resting) + O2(steady-rate)[1 - e].

Results: Two subjects did not adhere to the physical activity guidelines and were excluded from data analysis. The following data are representative of the remaining 38 subjects. The mean O2 uptake TC value for the 3 sessions was 33.67 +/- 7.87, 34.59 +/- 7.57, and 32.59 +/- 6.64 seconds, respectively. The intraclass correlation coefficient for the O2 uptake TC was 0.84 (P < .001).

Conclusions: The results of the present study indicate O2 uptake on-kinetics may be reliably measured using a single testing session. Multiple testing sessions, which would limit the potential clinical application of O2 uptake on-kinetics, may therefore not be necessary. Future research should be directed toward determining if O2 uptake on-kinetics is equally reliable in patient populations.