Effects of a Short-Term Resistance-Training Program on Heart Rate Variability in Children With Cystic Fibrosis-A Randomized Controlled Trial.

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. 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. Nineteen subjects (13 boys) were included (CON = 11; and EX = 8). Mean age was 12.2 ± 3.3, FEV (forced expiratory volume in the first second) z-score was 1.72 ± 1.54 and peak oxygen consumption (VOpeak) 42.7 ± 7.4 mL.Kg.min. Exercise induced significant changes in the frequency-domain variables, including a decrease in LF power ( = 0.001, = 0.98) and LF/HF ratio ( = 0.020, = 0.92), and an increase in HF power ( = 0.001, = -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 ( = 0.152, = -0.41) and RMSSD ( = 0.059, = -0.49) compared to the CON group. 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. www.ClinicalTrials.gov, identifier NCT04293926.