An Intensified Training Period Reduces REM Sleep but this Decline Can Be Mitigated by Ketone Ester Supplementation

INTRODUCTION: We previously showed that a strenuous training day disrupts sleep efficiency and REM sleep, and that these disturbances can be counteracted by ketone monoester (R)-3-hydroxybutyl-(R)-3-hydroxybutyrate (KE) supplementation. However, the impact of prolonged intensified training on sleep quality, as well as the potential modulating effect of KE are unknown. METHODS: We performed a double-blind study in which twenty-four trained male athletes completed a 7-week training program with a gradual increase in training load while receiving either 25g of a control drink (CON, n=12) or 25g of KE (n=12) after each training session and 30 minutes before sleep. At the start (PRE), week 3 (MID), and the end (POST) of the training program, we evaluated sleep using polysomnography, and perceived stress/recovery balance using the REST-Q questionnaire. Timing, duration, and relative intensity of exercise on each testing day were identical. RESULTS: The progressive increase in training load induced a decrease in the perceived stress-recovery state in both groups (PRE: 73±21 vs. POST: 40±37, p<0.001, Hedges' g = 1.097). From PRE to MID, sleep efficiency improved by 3% in both groups (p=0.003, Hedges' g = 0.663) while wakefulness after sleep onset reduced by 2% (p=0.031, Hedges' g = 0.716). However, from PRE to POST, total REM sleep decreased by 2% in CON but increased by 3% in KE (p=0.002, for KE vs. CON, Hedges' g = 0.939). Perceived sleep quality did not differ between groups throughout the intervention. CONCLUSIONS: Our data indicate that KE supplementation did not enhance the beneficial effect of an initial increase in training load on sleep but prevented the decline in REM sleep upon a further training load increment.