Ventilation: a Reliable Indicator of Oxygen Consumption During Physical Activities of Various Intensities? (P222)

Several methods have tried to quantify physical activity using the relation between heart rate (HR) and oxygen consumption (\( \dot V \)O2). Considering the limits of this relation, we focus our work on another physiological index: ventilation (\( \dot V \) E). The aim of this study is to show that \( \dot V \) E is more strongly correlated with \( \dot V \)O2 than HR. Eight male subjects carried out four physical activities of various intensities: walking at 4 km.h−1, walking at 4 km.h−1 with load, running at 8 km.h−1 and cycling at 60 W. The ventilatory parameters (\( \dot V \)O2 and \( \dot V \) E) were measured by a portable indirect calorimetry system (VO2000 MedGraphics) and HR was measured with a cardiofrequencemeter. Coefficients of determination (r2 linear) of the relations \( \dot V \)O2=f(\( \dot V \) E) and \( \dot V \)O2=f(HR) were calculated for each subject (on each activity [r2 Ttot: 64 regressions], on all the four activities [r2 4activities: 16 regressions]) and then for the eight subjects joined together on all the four activities (r2 global: 2 regressions). Results showed that the r2 Ttot of the relation \( \dot V \)O2=f(\( \dot V \) E) were significantly higher than those of the relation \( \dot V \)O2=f(HR) for the tasks: walking at 4 km.h−1 (p<0.001), walking at 4 km.h−1 with load (p<0.001), running at 8 km.h−1 (p<0.05). The mean values of r2 4activity of the relation \( \dot V \)O2=f(\( \dot V \) E) were significantly higher than those of the relation \( \dot V \)O2=f(HR)(p≤0.001). Finally, the r2 global of the relation \( \dot V \)O2=f(\( \dot V \) E) were higher than those of the relation \( \dot V \)O2=f(HR). In view of these results, it seems that \( \dot V \) E is more strongly correlated with \( \dot V \)O2 than HR. This approach seems very promising in order to develop a new method for the quantification of physical activity. Nevertheless, other experiments with a more significant number of subjects and activities have to be carried out to validate this first study.