Training-induced Changes In The Control Of Heart Rate Throughout A Competitive Season In Collegiate Female Swimmers.

Abstract

In competitive swimming, overload training is often used to elicit transient states of overreaching in the hopes that subsequent periods of taper will lead to performance supercompensation. However, if the overload stress is too great relative to the level of recovery, fatigue will accumulate and cause both a greater risk of injury and more prolonged decrements in performance. Measures of vagal control of the heart rate (HR) have been shown to reflect the balance between training-induced fatigue and recovery, and so those measures can provide valuable feedback to help guide coaches as they develop and revise training plans. PURPOSE: The purpose of the present study was to use three different indicators of vagal control of HR to investigate the impact of overload training and tapering in collegiate female swimmers. Those indicators were the resting logarithm of the root mean square of successive R-R intervals (lnRMSSDrest), HR responses to forced breathing (HRdiff), and HR responses to one minute of sustained handgrip exercise (HRhg). METHODS: Thirteen female Division-1 swimmers performed lnRMSSDrest, HRdiff, HRhg assessments three times throughout their competitive season: 1. at the beginning of the season (BL), 2. eleven weeks later during a period of intense overload training (OL), and 3. another eleven weeks later and following a taper (TP). Differences in the cardiovascular variables during BL, OL, and TP were determined using repeated measures ANOVAs. RESULTS: Very large decreases in lnRMSSDrest (p<0.01) and increases in HRhg (p<0.05) occurred during OL, but those values then returned to BL levels during TP (p<0.05 and p<0.01, respectively). By contrast, HRdiff values fell progressively throughout the season, and there was a large difference between the BL and TP measurements (p<0.05). CONCLUSION: Changes in all three variables demonstrated that OL impaired vagal stimulation of the heart, and the bulk of evidence indicated that vagal stimulation was fully restored during TP. This was one of only a few longitudinal studies that have investigated the control of HR over the course of an entire competitive swim season, and it was the first study to demonstrate that overload training and taper can alter HR responses to both forced breathing and sustained handgrip exercise.