RESUMEN
BACKGROUND: Slow breathing has been used to improve psychophysiological regulation due to positive action on the autonomic nervous system. PRIMARY STUDY OBJECTIVE: We evaluated the effects of slow breathing on heart rate autonomic control in preschool-aged children. METHODS/DESIGN: Prospective clinical study. SETTING: Campinas, Brazil. PARTICIPANTS: We included 42 children in the experimental group (age 5.7 ± 0.3) and 33 children in the control group (age 6.2 ± 0.3). INTERVENTION: Children received a daily training of eight weeks duration for practicing a slow breathing technique. Primary Outcome Measures ⢠We analyzed heart rate variability (HRV) and cardiorespiratory coherence at rest under spontaneous breathing and during respiratory sinus arrhythmia (RSA) at the end of the 1st, 4th, and 8th weeks of training. RESULTS: The percentage of high coherence ratio increased (P < .0001), HRV reduced (SDNN, P = .0066; RMSSD, P = .0015; pNN50, P < .0001; SD1, P = .0015; SD2, P = .0166) and the complexity of HRV increased (ApEn, P = .0004; MSE area, P < .0001; DFAαl, P = .0001; ShanEnt, P = .0106; Lmean, P = .0066) during RSA compared to spontaneous breathing after slow breathing training period. CONCLUSION: Slow breathing training exercise induced increased cardiorespiratory coherence and increased nonlinear behavior of heart rate dynamics suggesting improvements in health status. Increased cardiorespiratory coherence reinforces the importance of including respiratory exercises in strategies that aim to promote physical health and self-regulation skills in educational settings.