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This study analyzed the effects of physical training programs on heart rate variability, as a measure of sympathovagal balance, in children and adolescents with chronic diseases. Relevant articles were systematically searched in Pubmed, Science Direct, Web of Science, Scopus, Google Scholar and Embase scientific databases. We performed a meta-analysis using an inverse variance heterogeneity model. Effect size calculation was based on the standardized mean differences between pre- and post-intervention assessments, assuring at least a single-group repeated-measures model for each extracted group. Ten studies (252 participants) were included, seven in obese subjects, two in type-1 diabetes, and one in cerebral palsy. When time-domain variables were analyzed, exercise was found to moderately increase RMSSD (SMD=0.478; 95%CI: 0.227 to 0.729; p <0.001), SDNN (SMD=0.367; 95%CI: 0.139 to 0.595; p =0.002) and pNN50 (SMD=0.817; 95%CI: 0.139 to 0.595; p =0.002). As for frequency-domain variables, exercise presented a moderate increasing effect on HF (SMD=0.512; 95%CI: 0.240 to 0.783; p <0.001), a negligible effect for LF (SMD=0.077; 95%CI: –0.259 to 0.412; p <0.001) and a non-significant reduction for LF/HF (SMD=–0.519; 95%CI: -1.162 to 0.124; p =0.114). In conclusion, physical training programs are able to modulate heart rate variability in children and adolescents with chronic diseases, affecting mainly the time-domain variables. [ABSTRACT FROM AUTHOR]

Background: Cystic fibrosis (CF) affects the autonomic nervous system (ANS) and exercise in healthy children modulates the interaction between sympathetic and parasympathetic activity. This study aimed to evaluate the effects of a short-term resistance exercise program on heart rate variability (HRV) in children and adolescents with CF. Methods: A randomized controlled trial was carried out in children diagnosed with CF aged 6–18 years. Individuals were divided into two groups: control (CON) and resistance-training (EX). Individuals in the EX group completed an individualized guided resistance program (5-RM—60–80%) for 8 weeks (3 sessions of 60 min/week). Upper and lower limbs exercises (seated bench press, seated lateral row, and leg press) were used. HRV was measured using a Suunto watch with subjects in lying position. Results: Nineteen subjects (13 boys) were included (CON = 11; and EX = 8). Mean age was 12.2 ± 3.3, FEV1 (forced expiratory volume in the first second) z-score was 1.72 ± 1.54 and peak oxygen consumption (VO2peak) 42.7 ± 7.4 mL.Kg–1.min–1. Exercise induced significant changes in the frequency-domain variables, including a decrease in LF power (p = 0.001, d = 0.98) and LF/HF ratio (p = 0.020, d = 0.92), and an increase in HF power (p = 0.001, d = −0.97), compared to the CON group. No significant changes were found for time-domain variables, although increases with a moderate effect size were seen for SDNN (p = 0.152, d = −0.41) and RMSSD (p = 0.059, d = −0.49) compared to the CON group. Conclusion: A short-term resistance exercise-training program was able to modulate HRV in children and adolescents with CF presenting mild to moderate lung function impairment and good physical condition. Clinical Trial Registration: www.ClinicalTrials.gov, identifier NCT04293926. [ABSTRACT FROM AUTHOR]