Comparison of oxygen uptake on-kinetic calculations during submaximalexercise

The mean response time (MRT) and time constant (TC) are two oxygen uptake (VO ₂) on-kinetic calculations whose values are presumed to be interchangeable. This study tests the assumption of uniformity among different VO ₂ on-kinetic calculations. Nineteen (13 male/6 female) apparently healthy subjects were recruited for this study. Mean age (±SD) for this group was 44.1±10.1 years. Subjects underwent a progressive exercise test and six-minute exercise session (1.6 m/hr, 3.0% grade) on separate days. Both breath-by-breath (bb) and 10-second averaged (avg) ventilatory expired gas data were used to produce four VO ₂ on-kinetic calculations (MRT _bb, MRT _avg, TC _bb, TC _avg). There were statistically significant differences (p<0.05) between TC _bb (17.6 s) and TC _avg (22.7 s), MRT _bb (22.9 s), and MRT _avg (24.7 s). Comparisons amongst TC _avg (22.7 s), MRT _bb (22.9 s), and MRT _avg (24.7 s) did not reach statistical significance (p>0.05). All VO ₂ on-kinetic calculations were significantly correlated with peak VO ₂, age, and each other. These results indicate that all MRT and TC calculations may not be interchangeable. All VO ₂ uptake on-kinetic expressions did, however, appear to represent aerobic capacity and were highly correlated with each other indicating that calculation method may not have an excessively negative impact.