Association Between Self-recorded Heart Rate Variability Profiles And Aerobic Fitness In Young Healthy Adults

Daily self-recorded heart rate variability (HRV) enables quantification of weekly averages and day-to-day fluctuation, providing a more complete profile of cardiac-autonomic function relative to isolated laboratory measures. The extent to which self-recorded values associate with aerobic fitness is unclear. PURPOSE: To evaluate the association between self-recorded HRV profiles and aerobic fitness in young healthy adults. METHODS: Men (n = 21, 24.4 ± 4.9 yrs, 178.6 ± 8.1 cm, 85.6 ± 13.2 kg) and women (n = 20, 21.4 ± 2.7 yrs, 163.3 ± 5.0 cm, 69.4 ± 12.0 kg) performed 60-s post-waking HRV recordings in supine and standing positions using a Bluetooth heart rate strap and smartphone application over 7 days. The 7-day average of the natural logarithm of the root-mean square of successive R-R interval differences (LnRMSSDavg, a parasympathetic HRV index) and the coefficient of variation (LnRMSSDcv, a marker of daily fluctuation) were recorded for analysis. Maximal oxygen uptake (VO2max) was obtained via a graded exercise test on a cycle ergometer following the observation period. RESULTS: Men had significantly greater VO2max (39.5 ± 6.4 vs. 28.1 ± 5.9 mL·kg·min-1, P < 0.0001), supine LnRMSSDavg (4.4 ± 0.3 vs 4.1 ± 0.5, P = 0.01), and standing LnRMSSDavg (3.5 ± 0.5 vs 3.1 ± 0.4, P < 0.05) than women. Supine (r = 0.55, P = 0.01) and standing (r = 0.59, P < 0.01) LnRMSSDavg were associated with VO2max in men. Supine LnRMSSDavg (r = 0.55, P = 0.01) and supine LnRMSSDcv (r = -0.58, P < 0.01) were associated with VO2max in women. CONCLUSIONS: Self-recorded HRV profiles exhibited significant associations with aerobic fitness in young healthy men and women. However, HRV responses to orthostasis may be influenced by fitness level in men but not women. Supported by Georgia Southern University Faculty Research Committee Seed Funding Award.