Exercise, Autonomic

The purpose of this study was to determine the difference in heart rate recovery (HRR) and heart rate variability (HRV) after a maximal treadmill test between white and black men. Sixty white (n = 30) and black (n = 30) college-age men volunteered as study subjects. All subjects performed a maximal graded exercise test on a treadmill. HRR was determined from the difference between HR recorded at maximal exercise and the HR recorded at 1-minute (HRR1) and 2-minutes (HRR2) post-exercise. HRV was analyzed in the supine position 5 min-utes before and between 25 to 30 minutes after the exercise protocol. The HRV was examined as the standard deviation of all successful R-R intervals (SDNN), normal-ized high frequency power (HFnu), and normalized low frequency to high fre-quency ratio (LFnu:HFnu). No difference was found in pre-exercise HRV or HRR1. However, racial differences were revealed in the following parameters: HRR 2 = 39.93 ± 8.87 beats.min-1 in whites and 46.16 ± 8.95 beats.min-1 in blacks (p <.01), post-exer-cise SDNN = 35.55 ± 16.58 ms in whites and 48.37 ± 22.51 ms in blacks (p <.05), post-exercise HFnu = 16.60 ± 12.24 ms2 in whites and 27.62 ± 15.52 ms2 in blacks (p <.01), and post-exercise LFnu:HFnu = 9.48 ± 6.51 in whites and 4.85 ± 5.01 in blacks (p <.01). The results of this study suggest that college-age black men have a faster parasympathetic rebound following maximal exercise compared to young white men