Title

Health Markers Are More Strongly Associated With Daily-averaged Versus Isolated Heart Rate Variability Measures

Document Type

Presentation

Publication Date

7-2019

Abstract

Presentation given at the National Strength and Conditioning Association National Conference, Washington, D.C.

Associations between heart rate variability (HRV), aerobic fitness and body composition are inconsistent, possibly due to daily fluctuation in HRV. PURPOSE: To assess correlations between HRV, aerobic fitness and body composition using isolated and daily-averaged HRV measures. A secondary aim was to determine the association between daily fluctuation in HRV (assessed by the coefficient of variation, CV), fitness and body composition. METHODS: Adult men (n = 10, age = 22 ± 3 years, height = 177 ± 7 cm, weight = 81 ± 6 kg) volunteered for this study. A graded treadmill test was used to determine maximal oxygen uptake (VO2max). Dual energy x-ray absorptiometry was used to assess body composition. Ultra-short (60-s) natural logarithm of the root mean square of successive R-R interval differences (LnRMSSD) was obtained while fasted and seated on three separate days within one week. LnRMSSD from a single recording (LnRMSSD_iso), the three-day average (LnRMSSD_avg) and the CV (LnRMSSD_CV) were used for analysis. RESULTS: Mean ± standard deviation for VO2max, body fat percentage (%BF) and fat mass (FM) were 51.1 ± 8.0 ml∙kg·min-1, 17.4 ± 5.7% and 13.9 ± 4.7 kg, respectively. LnRMSSD_avg demonstrated stronger associations than LnRMSSD_iso with VO2max (r = 0.64, p = 0.04 vs. r = 0.47, p = 0.17), %BF (r = -0.57, p = 0.08 vs. r = -0.53, p = 0.11) and FM (r = -0.59, p = 0.07 vs. = -0.51, p = 0.13). LnRMSSD_CV was positively associated with %BF (r = 0.64, p = 0.04), FM (r = 0.70, p = 0.02) and negatively, but non-significantly associated with VO2max (r = -0.48, p = 0.16). CONCLUSIONS: The association between HRV, fitness and body composition is strengthened when using daily-averaged HRV measures. The magnitude of fluctuation in day-to-day HRV may also be a relevant health marker and should not be dismissed as “noise”. PRACTICAL APPLICATIONS: Practitioners and clinicians should acquire a series of HRV measures when assessing cardiac-autonomic activity in an individual. These findings are most relevant for research or practice involving sedentary and clinical populations given that greater daily fluctuation in LnRMSSD was observed among individuals with lower aerobic fitness and greater body fat.

Sponsorship/Conference/Institution

National Strength and Conditioning Association National Conference

Location

Washington, D.C.

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