Relationships Between Sport Specialization, Sleep, and Subjective Well-Being in Female Adolescent Athletes.

Objective: To evaluate the relationship between sport specialization, sleep, and subjective well-being in female youth soccer players. Design: Prospective cohort study. Setting: Community soccer organization. Methods: During a 4-month season, 52 female youth soccer players (aged 13-18 years) reported daily training load (TL) and every morning recorded sleep duration and stress, mood, fatigue, soreness, and sleep quality from 23 (worst) to +3 (best). As all the athletes participate in soccer as their primary sport for over 8 months of the year, players were considered specialized if they participated in soccer exclusively and had previously quit another sport to focus on soccer. Least-square mean values from linear mixed effects models were used to compare TL, subjective well-being, and sleep while adjusting for individual repeated measures. Results: Daily TL during the season did not differ between specialized and nonspecialized athletes (412624 vs 415619 arbitrary units, P = 0.96, respectively). Despite similar nightly sleep duration (8.10 +/- 0.14 vs 8.25 +/- 0.11 hours, P = 0.42), specialized athletes were found to have lower (worse) fatigue (1.02 +/- 0.14 vs 1.50 +/- 0.11, P = 0.010), soreness (0.66 +/- 0.18 vs 1.23 +/- 0.14, P = 0.013), mood (1.32 +/- 0.12 vs 1.72 +/- 0.10, P = 0.013), and sleep quality (1.07 +/- 0.13 vs 1.42 +/- 0.10, P = 0.035) than the nonspecialized group. Although stress was lower (worse) among the specialized athletes, the difference was not statistically significant (0.97 +/- 0.16 vs 1.32 +/- 0.13, P = 0.092). Conclusions: Among female youth soccer players, sport specialization was associated with impairments in subjective well-being and sleep quality. Additional research is necessary to determine whether this relationship is causal or if factors that influence sport specialization also influence sleep and subjective well-being.