Oxygen uptake kinetics in trained athletes differing in $$\dot V_{{\text{O}}_{{\text{2max}}} }$$

Previous work has shown that when \(\dot V_{{\text{O}}_{\text{2}} }\) kinetics are compared for endurance trained athletes and untrained subjects, the highly trained athletes have a faster response time. However, it remains to be determined whether the more rapid adjustment of \(\dot V_{{\text{O}}_{\text{2}} }\) toward steady state in athletes is due to \(\dot V_{{\text{O}}_{{\text{2max}}} }\) differences or training adaptation alone. One approach to this problem is to study the time course of \(\dot V_{{\text{O}}_{\text{2}} }\) kinetics at the onset of work in athletes who differ in \(\dot V_{{\text{O}}_{{\text{2max}}} }\) but have similar training habits. Therefore, the purpose of these experiments was to compare the time course of \(\dot V_{{\text{O}}_{\text{2}} }\) kinetics at the onset of exercise in athletes with similar training routines but who differ in \(\dot V_{{\text{O}}_{{\text{2max}}} }\) . Ten subjects ( \(\dot V_{{\text{O}}_{{\text{2max}}} }\) range 50–70 ml · kg⁻¹ · min⁻¹) performed 6-minutes of cycle ergometer exercise at ∼50% \(\dot V_{{\text{O}}_{{\text{2max}}} }\) . Ventilation and gas exchange were monitored by open circuit techniques. The data were modeled with a single component exponential function incorporating a time delay, (T _D ); \(\Delta \dot V_{{\text{O}}_{{\text{2}}f} } = \Delta \dot V_{{\text{O}}_{2ss} } {\text{ (1}} - e^{ - t - T_D /_{\tau )} }\) , where Τ is the time constant \(\Delta \dot V_{{\text{O}}_{{\text{2}}f} }\) is the increase in \(\dot V_{{\text{O}}_{\text{2}} }\) at time t and \(\Delta \dot V_{{\text{O}}_{{\text{2ss}}} }\) is the steady-rate increment above resting \(\dot V_{{\text{O}}_{\text{2}} }\) . Kinetic analysis revealed a range of \(\dot V_{{\text{O}}_{\text{2}} }\) half times from 21.6 to 36.0 s across subjects with a correlation coefficient of r=−0.80 (p<0.05) between \(\dot V_{{\text{O}}_{{\text{2max}}} }\) and \(\dot V_{{\text{O}}_{\text{2}} }\) half time. These data suggest that in highly trained indicivuals with similar training habits, those with a higher \(\dot V_{{\text{O}}_{{\text{2max}}} }\) achieve a more rapid \(\dot V_{{\text{O}}_{\text{2}} }\) adjustment at the onset of work.