Skinfold Thickness is Related to Cardiovascular Autonomic Control as Assessed By Resting Heart Rate Variability

INTRODUCTION: Heart rate variability (HRV) is a widely used non-invasive indicator of cardiovascular autonomic modulation and is an important predictor of cardiovascular disease. There is substantial evidence to show that autonomic control of heart rate is related to body composition. Most studies also show an improved HRV profile with long-term aerobic exercise. Thus, the use of HRV has also become a popular tool to monitor the positive cardiovascular benefits that occur with weight loss and/or with aerobic exercise training. Because aerobically fit subjects generally have healthy body composition, the influences of aerobic fitness and body composition on HRV may frequently confound each other. The purpose of this study was to determine if resting HRV is related to maximal aerobic fitness and the selected body composition measurements as follows: body mass index (BMI), waist circumference (WC) and the sum of skinfold thickness (SUMSF). METHODS: Fifty men (age = 21.9 +/− 3.0 years, height = 180.8 +/− 7.2 cm, weight = 80.4 +/− 9.1 kg) volunteered to participate in this study. For each subject, BMI, WC, and the SUMSF across the chest, abdomen and thigh regions were recorded. Heart rate variability (HRV) was assessed during a 5-minute period while the subjects rested in a supine position. The following frequency domain parameters of HRV were recorded: normalized high frequency power (HFnu), and low frequency to high frequency power ratio (LF:HF). To determine maximal aerobic fitness (i.e., V̇o2max), each subject performed a maximal graded exercise test on a treadmill. RESULTS: SUMSF was the only variable that held a significant independent correlation to HFnu (r = −0.40, p < 0.01), and LF:HF (r = 0.44, p < 0.01). The results of the regression procedures showed that SUMSF accounted for the greatest variance in HFnu (R2 = 0.16, p < 0.01), and LF:HF (R2 = 0.20, p < 0.01). CONCLUSIONS: The results of this study suggest that resting HRV was significantly related to SUMSF, but not V̇o2max, WC, or BMI. PRACTICAL APPLICATION: This study showed the importance of the simple technique of measuring skinfold thickness in relation to cardiovascular autonomic control of heart rate. The HRV parameters analyzed in this study (i.e., HFnu and LF:HF) were significantly related to SUMSF, but not V̇o2max, WC, or BMI. The skinfold technique is a commonly used field measure for predicting body fat percentage. Therefore, exercise training should perhaps induce an improve body fat mass to appreciably augment cardiovascular autonomic modulation.