Aidan Lewis1, Justin DeBlauw1, Derek A. Crawford2, Katie M. Heinrich1, FACSM

1Kansas State University, Manhattan, KS; 2University of Central Missouri, Warrensburg, MO

Higher resting heart rate (RHR) is positively associated with higher all-cause mortality. Aerobic exercise training helps lower RHR. High intensity functional training (HIFT) has had similar effects in women, but is unexplored among men. Heart rate variability (HRV) monitoring can assess individual adaptation and allow for more precise HIFT prescription and beneficial cardiovascular adaptations. PURPOSE: To determine effects of HRV-modulated HIFT on RHR and HRV changes. METHODS: Healthy adults (N = 55) were randomly assigned to HIFT (n = 29, age = 24.1 ± 4.1 years, 41.4% men) or HIFT-HRV modulated (n = 26, age = 23.7 ± 4.5, 53.8% men) groups. Both groups completed 11-weeks of daily HRV recordings with a validated smart phone application and 6-weeks of HIFT (5 d·week-1) and were assessed pre and post for changes in RHR, HRV and coefficient of variance (CV) in HRV. Meaningful changes in resting HRV were used to modulate (i.e., reduce) HIFT-HRV participants’ exercise intensity. Linear mixed models were used with the Bonferroni post hoc adjustment to look at RHR, HRV, and CV in HRV. RESULTS: No significant main effects for group, sex, or time were found for change in HRV (ps = .09-.40) or for group or time for changes in the CV in HRV (ps = 0.38-0.75). However, there was a significant main effect for gender on the change in CV in HRV (F= 6.23; mean difference= 1.82 ± 0.73; 95% CI= 0.39, 3.25; p = 0.016) with men significantly greater than women. Main effects for group and sex were not significant for RHR change (ps = 0.060.93). However, there was a significant main effect for time (F= 4.89; mean difference= -3.25 ± 1.47; 95% CI= -6.14, -0.37; p = 0.035) with a reduction in resting HR being observed in both groups. CONCLUSION: HIFT training prescription, modulated by daily HRV, produced similar changes in RHR while producing a greater change in the CV in HRV for men. HRV modulated HIFT resulted in beneficial cardiovascular adaptations which has positive implications for reducing the all-cause mortality rate.

ACKNOWLEDGEMENTS: This study was funded by the Mindlin Foundation and the Kansas State University Office of Undergraduate Research and Creative Inquiry.

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