Impact of Sleep Restriction and Intensified Training on Mucosal Immunity and Psychological Responses in Young Soccer Players.

de Morais Ferreira, AB, Halson, S, Galvão-Coelho, NL, de Almeida, RN, Nakamura, FY, and Mortatti, AL. Impact of sleep restriction and intensified training on mucosal immunity and psychological responses in young soccer players. J Strength Cond Res 40(7): e703-e713, 2026-This study analyzed the effects of training intensification during a period of sleep restriction (SR) on mucosal immunity (salivary IgA), upper respiratory tract health, mood states, and stress tolerance in young soccer players. Sixteen male youth soccer players completed 7 weeks of training with varied workloads. Weeks 3 and 5 involved a 75% increase in internal training load (ITL); however, although sleep was unrestricted in week 3, allowing for an increase in total sleep time (TST) (+53 minutes vs. baseline), week 5 included a ∼10% reduction in TST (-44 minutes vs. baseline). Internal training load was assessed using session-rating of perceived exertion, and sleep was monitored via actigraphy. Salivary IgA, upper respiratory tract infection (URTI) severity (Wisconsin Upper Respiratory Symptom Survey), perceived recovery status (PRS), stress tolerance (Daily Analysis of Life Demands of Athletes), and mood states (Brunel Mood Scale) were evaluated weekly. Salivary IgA concentrations significantly decreased in both intensified training weeks (week 3: β = -87.41, p = 0.007; week 5: β = -114.04, p < 0.001). However, only in week 5, this reduction was accompanied by a significant increase in URTI severity ( p = 0.001), heightened fatigue (χ 2 (6) = 42.499, p < 0.001), reduced vigor (χ 2 (6) = 49.422, p < 0.001), impaired PRS ( p < 0.001), and lower stress tolerance ( p = 0.001). In contrast, during week 3, despite the intensified training, PRS, mood states, and stress tolerance remained stable. These findings emphasize the protective role of adequate sleep during intensified training, as greater sleep availability in week 3 may have mitigated the negative effects observed in week 5. Ensuring sufficient sleep during periods of high training loads is essential to maintain physical and psychological health.