Examining the Exercise Dose-Response Using Cardiac Autonomic Activity in Female University Ice Hockey Players.

Female university ice hockey players experience elevated and sustained cardiovascular stress during training and competition. There remains limited research on the "exercise dose-response" in female ice hockey players. The purpose of this study was to examine daily and weekly changes in cardiac autonomic activity across a competitive season, and to examine its association with accumulated exercise stress. Twenty-one female ice hockey players wore chest strap heart rate monitors to quantify exercise heart rate dynamics into a training load (TL) metric and time (min) performing high-intensity activity (HIA) during training and competition. Cardiac autonomic activity was expressed as both resting heart rate (RHR) and the root mean squared of successive R-R intervals (rMSSD) and was recorded immediately upon awakening each morning. The association between HRV and both TL (r = -0.420, p = 0.058) and HIA (r = -0.420, p = 0.058) was observed. The association between RHR and both TL (r = 0.109, p = 0.638) and HIA (r = 0.150, p = 0.516) was observed. rMSSD fell below the typical error for ~50% of games. In conclusion, HRV demonstrated greater sensitivity to exercise stress than RHR for quantifying the dose-response to on-ice exercise stress.