Comparison of oxygen kinetics in young and old subjects

Summary

Five older men (aged 60–69 yr) and five young men (aged 21–29 yr) with approximately equal levels of age-corrected$\dot VO_2$ max were compared with respect to oxygen kinetics at equal absolute workloads (100 watts) and at equal relative workloads (45%$\dot VO_2$ max) on a cycle ergometer. At 45%$\dot VO_2$ max, half times for$\dot VO_2$ response to instantaneous transition from unloaded pedalling were 30.0 s and 27.4 s for old and young respectively (t=0.260,p<0.80). No significant differences were found in the$\dot V_E$ response and by inference none existed in O₂ extraction. Mean half times for heart rate responses at a workload of 100 W were 24.2 s and 20.6 s for old and young groups respectively (t=0.722,p<0.49). Mechanical efficiency estimated from steady state data at 100 W was 19.8% and 20.5% for old and young groups respectively (t=0.574). The close similarity in responses to submaximal work in old and young subjects of equivalent fitness suggests caution in the interpretation of agewise decrements observed in physiological variables which may be sensitive to physical fitness status.