Association of sleep efficiency with cardiac autonomic modulation in young and professional soccer players during pre-season

OBJECTIVE: This study investigated the association between sleep efficiency and cardiac autonomic modulation in young and professional soccer players during pre-season. METHODS: A cross-sectional quantitative study was conducted with 53 male soccer players divided into three categories: U-15 (n = 12), U-17 (n = 15), and professionals (n = 26). Sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI), cardiac autonomic modulation via heart rate variability (HRV) recorded by a 10-lead electrocardiograph and analyzed with Kubios HRV 2.0, and cardiorespiratory capacity estimated through the Yo-Yo Intermittent Recovery Test. Body composition was assessed by tetrapolar electrical bioimpedance. Statistical analyses included one-way ANOVA, Welch's ANOVA, chi-square and Fisher's exact tests, Pearson correlation, and simple linear regression, with significance set at p < 0.05. RESULTS: Professional athletes demonstrated significantly higher VO₂max (50.5 ± 4.56 ml·kg⁻¹·min⁻¹; p < 0.001), lower resting heart rate (54.9 ± 8.65 bpm; p = 0.03), and greater parasympathetic modulation (RMSSD: 82.8 ± 17.5 ms; p < 0.001) compared to youth categories. Sleep efficiency was significantly higher in professionals (90.7 ± 6.13%; p = 0.01) and positively correlated with RMSSD. A significant association was found between RMSSD levels and global sleep quality (p = 0.004; X² = 0.50), as well as between RMSSD and VO₂max classification (p = 0.01; X² = 0.40). CONCLUSION: Sleep efficiency is positively associated with cardiac autonomic modulation and aerobic performance in soccer players. While the superior physiological profile of professionals reflects a synergy between training adaptations and biological maturation, HRV and PSQI constitute complementary monitoring tools for integrated athlete assessment across competitive categories.