1. Arena, Ross PhD, PT

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The analysis of oxygen (O2) uptake on-kinetics has been shown to be reflective of cardiovascular and musculoskeletal function. While the amount of evidence demonstrating the clinical validity of this variable is robust, debate over defining a reliable method for the measurement of O2 uptake on-kinetics continues.



To assess the short-term reliability of O2 uptake on-kinetics in a group of apparently healthy individuals.



Forty apparently healthy subjects (20 male/20 female) participated in treadmill exercise sessions on three consecutive days. Subjects were instructed to maintain a similar physical activity pattern during the three-day period. During each session, O2 uptake was collected at rest for two minutes and during ambulation at 2.2 miles per hour and 6% grade for six minutes. Breath-by-breath O2 uptake data was averaged over 10-second intervals before data analysis. Resting O2 uptake was defined as the averaged value of two minutes of data in the seated position. Steady-rate O2 uptake was the averaged value during the final two minutes of the exercise session. The time constant (TC) for the O2 uptake response was calculated for each of the three sessions using the equation: VO2 (any time) = VO2 (resting) + VO2 (steady-rate increase)(1 - e-(t/TC)).



Two male subjects did not maintain a similar activity pattern and were excluded from data analysis. The intraclass correlation coefficient for resting O2 uptake, steady-rate O2 uptake and the O2 uptake TC was 0.92, 0.98 and 0.84 respectively. The standard error of measurement, with 95% confidence bounds, for the O2 uptake TC was +/-5.77 seconds.



These results of the present study indicate O2 uptake on-kinetics may be reliably measured using a single testing session. Future research should be directed toward determining if O2 uptake on-kinetics is equally reliable in other populations such as those diagnosed with heart failure.