Influence of Sleep Quality on Recovery and Performance in Endurance and Ultra-Endurance Runners: Sex Differences Identified Through Hierarchical Clustering

Background: Assessing sleep quality is essential in sports science, particularly in ultra-endurance sports, where recovery is critical for performance and health. Objective: This study aimed to identify sleep quality patterns among endurance and ultra-endurance athletes using hierarchical clustering analysis, with comparisons by sex and modality. Method: Data were collected during the La Misi & oacute;n Brasil competitions in 2023 and 2024, using the Pittsburgh Sleep Quality Index (PSQI). The questionnaire was emailed to all registered runners two weeks before the event. A total of 490 athletes participated, including 276 men (mean +/- SD age: 43 +/- 11 years) and 214 women (mean +/- SD age: 43 +/- 13 years). Statistical analyses included Cohen's d and r effect sizes, and a 95% confidence interval for hypothesis testing. Residuals between-cluster proportions were assessed within a range of -3.3, ensuring a 99.7% confidence level for significant differences. Results: The results showed that endurance runners had better sleep quality, with most scoring low on the PSQI. In contrast, ultra-endurance athletes displayed greater variability, with a higher prevalence of poor sleep quality, particularly in women. Conclusions: The hierarchical clustering method effectively identified distinct sleep patterns, providing insights into the dynamics of recovery and performance. These findings highlight the impact of increased physical and psychological demands in ultra-endurance sports and emphasize the need for tailored sleep monitoring strategies to optimize the recovery and performance of athletes.