Effects of Training Load on Sleep Characteristics, Hormonal, and Immune Responses of Adolescent Female Water Polo Athletes.

PURPOSE To compare the sleep behavior, cortisol, and immunoglobulin A responses between 2 conditions; an experimental condition consisting of 2 consecutive weeks of school and training commitments with low- and high-load training and a 3-day control condition without school and training obligations. METHODS Objective sleep characteristics were monitored using ActiGraphy in 11 female water polo athletes (age: 12.9 [1.2] y) during both conditions. In the experimental condition, a low-load training week was followed by a high-load training week. Salivary cortisol and immunoglobulin-A were measured before training. RESULTS Sleep duration was lower and awakenings were fewer in experimental condition compared to control condition (duration: 464.1 [20.6] vs 501.3 [85.0] min, P = .02, d = 0.66; awakenings: 17.4 [8.4] vs 21.1 [10.2], P = .02, d = 0.71). Sleep characteristics were similar between training conditions; however, variability in time in bed and total sleep time was lower during high- (12.34% [6.46%] and 13.32% [7.59%]) than low-load training (16.30% [7.43%] and 17.32% [5.50%]) (P < .01, d = 1.12 and P = .04, d = 0.70). Salivary cortisol and immunoglobulin-A levels were higher during high-load than low-load training (P < .01, d = 1.02 and P < .01, d = 1.38). CONCLUSIONS School and sports training commitments reduce sleep duration but improve sleep quality in adolescent water polo athletes, while high-load training reduces sleep variability and increases allostatic load without altering sleep characteristics.