Early Improvement in Cardiac Autonomic Modulation After a Recreational Physical Training Program in Healthy Children.

Physical activity is known to influence cardiovascular regulation in children. However, evidence regarding cardiac autonomic responses to recreational physical training (RPT) in healthy pediatric populations remains limited. Thus, this study aimed to investigate changes in cardiac autonomic modulation associated with a RPT program in healthy children. We conducted a quasi-experimental pre-post intervention study including healthy children who participated in a 10-week RPT. Cardiac autonomic modulation was assessed at rest using short-term heart rate variability (HRV) analysis. HRV measurements (time- and frequency-domain), anthropometric, hemodynamic, and cardiorespiratory variables were evaluated before and after the intervention. Effect sizes were calculated to estimate the magnitude of observed changes. Seventy-four participants (31 girls and 43 boys; mean age 8.6 ± 0.9 years) were included. Following the intervention, significant increases were observed in time-domain HRV measurements, including SDNN (standard deviation of normal RR intervals; pre- 49.1 ± 2.1, post- 61.9 ± 2.1 ms; p < 0.01) and RMSSD (root mean square of successive differences between normal RR intervals; pre- 52.1 ± 2.7, post- 65.2 ± 2.7 ms; p < 0.01), with large effect sizes. No significant changes were detected in blood pressure, estimated peak oxygen uptake, or frequency-domain HRV. Waist circumference decreased (pre- 66.2 ± 2.0, post- 65.2 ± 2.0 cm; p < 0.01), whereas body mass index percentile remained unchanged. Therefore, participation in a RPT was associated with favorable changes in cardiac autonomic modulation in healthy children, particularly in measurements reflecting global variability and parasympathetic activity. These findings suggest that RPT may elicit early autonomic adaptations during childhood, even in the absence of measurable changes in traditional cardiovascular risk markers.