Intensified Olympic Preparation: Sleep and Training-Related Hormonal and Immune Responses in Water Polo

To investigate whether sleeping activity, hormonal responses, and wellness are altered in elite water polo players during their preparation toward the Tokyo Olympics.

Eight elite-level water polo players participated in 3 consecutive training phases: (1) before the commencement of a residential-based conditioning camp (PRE-CAMP; 3 d), (2) residential-based conditioning camp (5 d), and (3) a congested period of training and competition (POST-CAMP; 8 d). Nocturnal sleep was monitored for 14 consecutive days in PRE-CAMP (2 d), CAMP (5 d), and POST-CAMP (7 d). Postawakening salivary cortisol, immunoglobulin-A, and subjective wellness were measured during PRE-CAMP, CAMP, and POST-CAMP, and internal training/match load (ITL) was calculated daily. The averaged values for dependent variables were compared among training phases and analyzed using linear mixed models.

At CAMP compared with PRE-CAMP, ITL was higher (P < .01), and sleep onset and offset were earlier (P < .01). At this period, sleep interruptions and salivary cortisol were higher (P < .01, d = 1.6, d = 1.9, respectively), and subjective wellness was worsened (P < .01, d = 1.3). At POST-CAMP, the reduction of workload was followed by increased sleep efficiency, reduced sleep interruptions, and moderately affected salivary cortisol, yet overall wellness remained unaltered. In POST-CAMP, 2 of the players demonstrated severe symptoms of illness.

At the highest level of the sport and prior to the Olympics, large increments in workload during a training camp induced meaningful sleep interruptions and salivary cortisol increases, both of which were reversed at POST-CAMP. We suggest that the increased workload alongside the inadequate recovery affects sleep patterns and may increase the risk of infection.