Abstract
Cardiac-locomotor synchronization (CLS) has been documented in humans performing various rhythmic activities but its functional role remains largely unknown. Therefore, the present study was conducted to determine whether CLS is associated with gas exchange efficiency and alters muscle O2 utilization. 21 healthy subjects performed incremental grade walking test on a treadmill at a constant speed for 20 min. Breath-by-breath gas exchange parameters and changes in deoxy- and oxyhemoglobin at the soleus muscle by NIRS were measured. CLS was defined as being present when the phase difference between heartbeat and cadence was fixed over 10 s with the SD being below 0.15. The changes in gas exchange and NIRS indices during CLS were evaluated as the differences between the observed and predicted values which were obtained by plotting each desynchronized parameter against time and fitted with a least squares regression line. Lower level of ventilatory equivalent for O2 and relative increase in deoxyhemoglobin and decrease in oxyhemoglobin were observed during CLS episode. These results indicate that CLS induces a shift toward more aerobic oxidative metabolism during exercise.
