Association of Body Composition and Aerobic Fitness on Heart Rate Variability and Recovery in Young-Adult Black Men

Background: The primary purpose of this investigation was to determine the differences in resting heart rate variability and heart rate recovery between norm-referenced aerobic fitness groupings, independent of body composition, in Black men. Additionally, we sought to clarify the independent relationships that heart rate variability and heart rate recovery displayed with maximal aerobic fitness and selected body composition measures. Methods: Body mass index, waist circumference, and the sum of skinfold thickness were determined in forty Black men (23 ± 3 years). Each subject assumed a supine position while heart rate variability was analyzed for 5-minute and recorded as normalized high-frequency power and normalized low-frequency power to normalized high frequency ratio. A graded exercise treadmill protocol was performed to attain maximal aerobic fitness. Heart rate recovery was recorded at 1- and 2-minute of a cool-down period. Heart rate variability and heart rate recovery were compared across two groups whose maximal aerobic fitness was either below or above the normative mean value for the age group of men. Results: The results indicated that heart rate variability was higher in the group whose maximal aerobic fitness was above the normative mean value compared with the lower fit group (p < 0.05), but the differences disappeared when adjusting for body composition (p > 0.05). Regression analysis revealed that the sum of skinfolds accounted for the variation in normalized high frequency power (R2 = 0.20, p < 0.05) and normalized low-frequency power to normalized high frequency ratio (R2 = 0.30, p < 0.05), while waist circumference accounted for the variation in heart rate recovery at 2-minute (R2 = 0.20, p < 0.05). Conclusion: The results suggest that heart rate variability and heart rate recovery hold independent relationships to body composition but not aerobic fitness in young-adult, Black men.