Association Between Self-Recorded Heart Rate Variability Profiles And Actigraphy-Derived Physical Activity In Young Healthy Adults

Abstract

Mobile devices facilitate daily heart rate variability (HRV) tracking and serve as a potential behavior modification tool for cardiovascular health. It is currently unclear whether serial self-recorded HRV measures are influenced by physical activity (PA) levels. PURPOSE: To evaluate the association between self-recorded HRV profiles and actigraphy-derived PA levels in young, apparently healthy adults. METHODS: Men (n = 21, 24.4 ± 4.9 years) and women (n = 20, 21.4 ± 2.7 years) self-recorded post-waking HRV for 60 s in supine and standing positions using a heart rate chest strap and mobile application over one week. The week average of the natural logarithm of the root-mean square of successive R-R interval differences (LnRMSSDavg, a vagal HRV index) and the coefficient of variation (LnRMSSDcv, a marker of day-to-day fluctuation) were assessed. Throughout the observation period, subjects wore a validated wrist-based activity monitor to determine average sedentary time; light, moderate, moderate-vigorous (MV), and vigorous (V) PA; and total steps. Aerobic capacity (VO2max) was obtained via a maximal cycle ergometer test post-observation. RESULTS: In men, no associations were observed between any HRV and PA variables (P > 0.05). In women, sedentary time (606 ± 108 min) was associated (r = 0.59) with supine LnRMSSDcv (9.8 ± 5.2%), MVPA (259 ± 74 min) was associated with standing (13.0 ± 4.4%) and supine LnRMSSDcv (r = -0.45 and -0.51, respectively), VPA (152 ± 54 min) was associated with supine LnRMSSDcv (r = -0.53), and total step count (13,209 ± 2,560) was associated (r = 0.45) with supine LnRMSSDavg (4.1 ± 0.5) (all P < 0.05). VO2max was associated with the same PA variables in women (P < 0.05), but none of the PA variables in men (P > 0.05). After adjusting for VO2max (28.1 ± 5.9 mL·kg·min-1), all associations between HRV and PA variables in women became non-significant (P > 0.05). CONCLUSIONS: Significant associations between self-recorded HRV profiles and actigraphy-derived PA levels that were only observed in women appear to be explained by fitness. Thus, PA tailored to the enhancement of aerobic capacity will likely yield the greatest HRV improvements, reflected in higher average values with less day-to-day fluctuation. Supported by Georgia Southern University Faculty Research Committee Seed Funding Award.