AUTHOR=Estévez-González Agustín Jesús , Donadio Márcio Vinícius Fagundes , Cobo-Vicente Fernando , Fernández-Luna Álvaro , Sanz-Santiago Verónica , Villa Asensi José Ramón , Iturriaga Ramirez Tamara , Fernández-del-Valle Maria , Diez-Vega Ignacio , Larumbe-Zabala Eneko , Pérez-Ruiz Margarita 

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

JOURNAL=Frontiers in Physiology

VOLUME=Volume 12 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2021.652029

DOI=10.3389/fphys.2021.652029

ISSN=1664-042X

ABSTRACT=Background: Cystic fibrosis (CF) affects the autonomic nervous system 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 to 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.