Pulmonary O2 uptake on-kinetics in rowing and cycle ergometer exercise

The purpose of this study was to characterise, for the first time, the pulmonary O2 uptake (V˙O2) on-kinetic responses to step transitions to moderate and heavy intensity rowing ergometer exercise, and to compare the responses to those observed during upright cycle ergometer exercise. We hypothesised that the recruitment of a greater muscle mass in rowing ergometer exercise (Row) might limit muscle perfusion and result in slower Phase II V˙O2 kinetics compared to cycle exercise (Cyc). Eight healthy males (aged 28 ± 5 years) performed a series of step transitions to moderate (90% of the mode-specific gas exchange threshold, GET) and heavy (50% of the difference between the mode-specific GET and V˙O2 max) work rates, for both Row and Cyc exercise. Pulmonary V˙O2 was measured breath-by-breath and the V˙O2 on-kinetics were described using standard non-linear regression techniques. With the exception of ΔV˙O2/ΔWR which was ∼12% greater for Row, theV˙O2 kinetic responses were similar between the exercise modes. There was no significant difference in the time constant describing the Phase II V˙O2 kinetics between the exercise modes for either moderate (rowing: 25.9 ± 6.8 s versus cycling: 25.7 ± 8.6 s) or heavy (rowing: 26.5 ± 3.0 s versus cycling: 27.8 ± 5.1 s) exercise. Furthermore, there was no significant difference in the amplitude of the V˙O2 slow component between the exercise modes (rowing: 0.34 ± 0.13 L min−1 versus cycling: 0.35 ± 0.12 L min−1). These data suggest that muscle V˙O2 increases towards the anticipated steady-state requirement at essentially the same rate following a step increase in ATP turnover in the myocytes, irrespective of the mode of exercise, at least in subjects with no particular sport specialism. The recruitment of a greater muscle mass in rowing compared to cycling apparently did not compromise muscle perfusion sufficiently to result either in slower Phase II V˙O2 kinetics or a greater V˙O2 slow component amplitude during heavy exercise.