Influence of light physical activity on cardiac responses during recovery from exercise in humans

To examine the influence of light exercise on cardiac responses during recovery from exercise, we measured heart rate (HR), stroke volume (SV), and cardiac output (Q˙c) in five healthy untrained male subjects in an upright position before, during, and after 10-min steady-state cycle exercise at an exercise intensity of 170 W, corresponding to a mean of 68 (SD 4)% of maximal oxygen uptake. The recovery phase was evaluated separately for three different conditions: 10 min of complete rest (passive recovery), 7 min of pedalling at 20-W exercise intensity followed by 3 min of rest (partially active recovery), and 7 min of pedalling at 40-W exercise intensity followed by 3 min of rest (partially active recovery), on an upright cycle ergometer. The time courses of decreases in HR in the two active recovery phases at different exercise intensities were almost identical to those in the passive recovery phase. However, the subsequent HR reductions during the rest after active recovery at 20 W and at 40 W were mean 7.5 (SD 4.4) and mean 10.0 (SD 3.1) beats · min−1, respectively, both of which were significantly larger (P<0.05 and P<0.005) than the corresponding reduction [1.4 (SD 2.5) beats · min−1] for passive recovery. The SV values at the two exercise intensities during the active recovery periods were maintained at levels similar to that during 170-W steady-state exercise. In contrast, the SV during passive recovery decreased gradually to a level significantly below the initial baseline level at rest before exercise (P<0.05). The resultant time courses of CO values during active recovery were significantly higher (each P<0.05) than that during passive recovery. It was concluded from these findings that light post-exercise physical activity plays an important role in facilitating the venous return from the muscles and in restoring the elevated HR to the pre-exercise resting level.