Vagal Response to 15-weeks of High-Intensity Functional Training: A Pilot Study

Abstract

The purpose of this investigation was to examine the training effects of a 15-week High-Intensity Functional Training (HIFT) on Autonomic Nervous System (ANS). Eleven apparently healthy college students participated in this study. Participants were enrolled in a 15-week CrossFit® training based academic course, two days a week. On the first and last scheduled day of class participants performed a HIFT trial and ANS activity was measured through Heart Rate Variability (HRV) for 10 minutes prior to and following each bout using the log-transformed square root of the successive R-R differences (lnRMSSD) and high frequency power (lnHF). A significant decreased was observed for the lnRMSSD after the HIFT trial before (Pre: 3.86 ± 0.39 vs. Post: 2.58 ± 1.12; P < 0.001) and after (Pre: 4.00 ± 0.46 vs. 1.96 ± 0.84; P < 0.001) the intervention. Similarly, the lnHF was significantly reduced before (Pre: 3.66 ± 0.36 vs. Post: 2.88 ± 0.86; P < 0.05) and after (Pre: 3.73 ± 0.41 vs. 2.69 ± 0.65; P < 0.001) 15-weeks of this intervention. The exercise modality known as HIFT was effective in improving repetitions completed during the HIFT trial, when comparing pre and post trials. The findings of this study suggest that resting HRV and post exercise vagal reactivation is not influenced by 15-weeks of a HIFT intervention.