Effect of exercise intensity on post-exercise oxygen consumption and heart rate recovery

Purpose

There is some evidence that measures of acute post-exercise recovery are sensitive to the homeostatic stress of the preceding exercise and these measurements warrant further investigation as possible markers of training load. The current study investigated which of four different measures of metabolic and autonomic recovery was most sensitive to changes in exercise intensity.

Methods

Thirty-eight moderately trained runners completed 20-min bouts of treadmill exercise at 60, 70 and 80 % of maximal oxygen uptake (VO_2max) and four different recovery measurements were determined: the magnitude of excess post-exercise oxygen consumption (EPOC_MAG), the time constant of the oxygen consumption recovery curve (EPOCτ), heart rate recovery within 1 min (HRR_60s) and the time constant of the heart rate recovery curve (HRRτ) .

Results

Despite significant differences in exercise parameters at each exercise intensity, only EPOC_MAG showed significantly slower recovery with each increase in exercise intensity at the group level and in the majority of individuals. EPOCτ was significantly slower at 70 and 80 % of VO_2max vs. 60 % VO_2max and HRRτ was only significantly slower when comparing the 80 vs. 60 % VO_2max exercise bouts. In contrast, HRR_60s reflected faster recovery at 70 and 80 % of VO_2max than at 60 % VO_2max.

Conclusion

Of the four recovery measurements investigated, EPOC_MAG was the most sensitive to changes in exercise intensity and shows potential to reflect changes in the homeostatic stress of exercise at the group and individual level. Determining EPOC_MAG may help to interpret the homeostatic stress of laboratory-based research trials or training sessions.