The Effect of Water Loading for Acute Weight Loss Following Fluid Restriction on Sleep Quality and Quantity in Combat Sports Athletes

Introduction: Combat sport athletes commonly engage in established and novel acute weight-loss strategies to achieve weight division targets. The effect of such practices on sleep is unknown. Methods: Twenty-two combat sports athletes wore wrist actigraphy devices for nine nights during a training camp and completed questionnaires assessing daytime sleepiness, insomnia, sleep apnoea and chronotype. Athletes were assigned to a control (CG) or water loading group (WLG). Both followed a low residue diet for 96h, and restricted fluid for 24h before weigh-in. Prior to restriction, the CG consumed 40ml/kg and WLG consumed 100ml/kg fluid daily. Results: Four athletes responded positively for the potential prevalence of sleep apnoea (2 CG/WLG), reporting subthreshold insomnia 8±4, athletes were assessed as having an “intermediate chronotype”. Sleep latency estimates in CG were longer on days 4/6 relative to 3 (p<0.05). There was a between-group difference for sleep latency on day 6, with CG taking 35 mins longer (95% CI 5-64mins, p=0.022) to fall asleep. Conclusion: Acute weight loss by means of a low residue diet, both with and without water loading before the fluid restriction is a safe and effective means of manipulating body mass to in the context of sleep.