Cardiac autonomic function and its association with cardiometabolic disease risk factors in Black South African children.

OBJECTIVE: This study evaluated the associations between cardiac autonomic nervous system (ANS) activity and cardiometabolic disease (CMD) risk factors among black South African children. DESIGN: The participants included 34 black South African children (11.85 ±â€¯0.89 y). CMD risk factors included waist circumference (WC), hip circumference (HC), body mass index z-score (BMI z-score), blood pressure (SBP, DBP), total cholesterol (TC), high density lipoprotein cholesterol (HDL), low density lipoprotein cholesterol (LDL), fasting glucose (FG), fasting insulin (FINS), and vessel stiffness index (SI). Heart rate variability was used to quantify cardiac ANS activity. RESULTS: lnRMSSD, pNN50 and lnSD1 were inversely associated with FINS (r = -0.33, p = 0.05; r = -0.36, p = 0.03; r = -0.41, p = 0.01), WC (r = -0.45, p = 0.01; r = -0.39, p = 0.02; r = -0.45, p = 0.01), and HC (r = -0.41, p = 0.01; r = -0.36, p = 0.03; r = -0.43, p = 0.01). HDL was positively associated with lnRMSSD (r = 0.37; p = 0.03) and lnSD1 (r = 0.37; p = 0.03) while, LDL was negatively associated with HF (r = -0.41; p = 0.01). Regression analysis identified WC as the primary predictor for parasympathetic modulation in time domain (lnRMSSD: r2 = 0.21, p = 0.01; pNN50: r2 = 0.18, p = 0.01) and non-linear domain (lnSD1: r2 = 0.21, p = 0.01). CONCLUSION: Elevated resting parasympathetic activity in children is associated with lower CMD risk factors and an elevation in the protective HDL.

Short-Term High-Intensity Interval Training Is Superior to Moderate-Intensity Continuous Training in Improving Cardiac Autonomic Function in Children.

OBJECTIVES: This study aimed to investigate the impact of 3 isocaloric exercise programs on cardiac autonomic nervous system (ANS) functioning in children. METHODS: One hundred nine children (39% boys and 61% girls) aged 10-13 years (mean 11.07 ± 0.81) were conveniently assigned to 1 of 4 groups as follows: Moderate-intensity continuous training (MICT; n = 29) at 65-70% of the predicted maximum heart rate (MHR), High-intensity interval training (HIIT; n = 29) at > 80% of the predicted MHR, HIIT and MICT combined on alternate weeks (ALT; n = 27), and a control group (n = 24). Morning ANS activity was assessed via analysis of heart rate variability (HRV), with the patient in supine position for 10 min, before and after the exercise intervention. DATA ANALYSIS: A 2-way analysis of variance was used to evaluate the effects of training on all HRV parameters (p < 0.05/4 = 0.0125). RESULTS: After 5 weeks of training, significant improvements were observed for ln of the standard deviation of normal-to-normal intervals (p < 0.0001), ln of the root mean square of successive difference (p < 0.0001), and ln of standard deviation 1 (p < 0.0001), with superior results reported in the HIIT group (effect size [ES] = 2.22, 2.69, and 2.69) compared with the MICT (ES = 1.67, 1.75, and 1.75) and ALT (ES = 0.87, 1.06, and 1.06) groups, respectively. CONCLUSION: Short-term HIIT seems to induce superior alterations in cardiac ANS activity compared to MICT and ALT in children through enhanced vagal activity.

Do Short-Term Exercise Interventions Improve Cardiometabolic Risk Factors in Children?

OBJECTIVES: To explore the impact of short-term exercise of varying intensity on traditional risk factors for cardiometabolic disease. STUDY DESIGN: A total of 109 children (mean age, 11.1 ± 0.8 years) were conveniently assigned to 5 weeks of moderate-intensity continuous training (MICT; n = 29) set at 65%-70% of maximum heart rate, high-intensity interval training (HIIT; n = 29; >80% maximum heart rate), combined training (HIIT + MICT; n = 27), or no training (control; n = 24). Two-way ANOVA (group × time) was used to evaluate the effects of training on all cardiometabolic disease risk factors. Effect sizes were calculated to assess the magnitude of difference. RESULTS: MICT, HIIT, and HIIT + MICT were associated with significantly improved resting heart rate (effect size, -0.4, -1.1, and -1.1, respectively; P < .0001), fasting glucose (effect size, -0.6, -0.9, and -0.1, respectively; P = .0004), peak oxygen consumption (effect size, 0.5, 0.9, and 0.5, respectively; P < .0001), and c-reactive protein (effect size, -0.2, -1.0, and -0.5, respectively; P = .0016). HIIT + MICT was significantly associated with reduced waist circumference (-5.4%; P < .0001) and waist-to-hip ratio (-2.5%; P < .0002) compared with MICT (7.0% and 6.3%, respectively) and HIIT (-0.5% and -1.3%, respectively). CONCLUSION: Short-term HIIT and MICT interventions are useful for improving cardiometabolic health in children. HIIT + MICT may provide superior reductions in central obesity indicators.