A 14-Day Sleep Hygiene Intervention Improves Aerobic Performance and Reduces Anticipatory Cortisol in University Soccer Players

Background: Sleep is a critical recovery mechanism for athletes, supporting hormonal regulation, muscle repair, and cognitive function. Dual-career athletes are particularly vulnerable to sleep disruption, which may impair performance and stress regulation. This study examined the effects of a 14-day sleep hygiene intervention protocol (SHIP) on aerobic and anaerobic performance, as well as anticipatory cortisol responses, in university-level soccer players. Methods: Thirty athletes (females: n = 14, 22.1 ± 3.3 y, 157.8 ± 6.0 cm, 53.5 ± 3.9 kg, males: n = 16, 21.5 ± 1.7 y, 167.5 ± 5.9 cm, 62.7 ± 5.4 kg) completed the Pittsburgh Sleep Quality Index (PSQI), provided pre-test salivary cortisol samples, and performed the Yo-Yo Intermittent Recovery Test Level 1 (YYIR1) and Repeated Anaerobic Sprint Test (RAST) before and after the intervention (adhering daily to 10–18 individualized sleep hygiene). Results: The SHIP significantly reduced sleep latency (p = 0.04) and increased sleep duration (p = 0.03), and PSQI scores (p < 0.001) in both sexes. Females showed marked increases in sleep duration (p = 0.002), while males showed improved latency (p = 0.07). Five behaviourally coherent clusters derived from the SHIP adherence explained a substantial proportion of variance (74.99%). Stimulant and metabolic regulation, and bedroom light and thermal environment control consistently predicted sprint and physiological outcomes (p < 0.05). Anticipatory cortisol decreased before both tests (p = 0.03–0.04). YYIR1 performance improved for the full cohort (p = 0.001). RAST times slowed slightly (p = 0.02), though fatigue index improved (p = 0.05). Conclusions: A short-term SHIP effectively enhanced sleep, reduced physiological stress, and improved key performance outcomes in collegiate athletes.