Rationale:

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.

Objectives:

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

Methodology:

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: VO_{2 (any time)} = VO_{2 (resting)} + VO_{2 (steady-rate increase)}(1 - e^-(t/TC)).

Results:

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.

Conclusion:

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.