Effects of Creatine Monohydrate Loading on Sleep Metrics, Physical Performance, Cognitive Function, and Recovery in Physically Active Men: A Randomized, Double-Blind, Placebo-Controlled, Crossover Trial

Background/Objectives: Creatine monohydrate (CrM) supplementation is well-established for enhancing physical performance and accelerating recovery in several sporting contexts. However, beyond these traditional performance benefits, its effects on sleep metrics and cognitive function have not been thoroughly investigated. This investigation aimed to determine the effect of a loading phase of CrM on sleep metrics, physical performance, psycho-cognitive aspects, and recovery in physically active men. Methods: In a randomized, double-blind, placebo-controlled crossover design, 14 physically active men ingested 20 g/day of CrM or placebo (PL) for 7 days, during which their habitual exercise routines were maintained and standardized across both intervention phases. Sleep metrics were monitored throughout the interventions using wrist-worn actigraphy. On the day following the completion of each supplementation phase, participants rated their sleep quality using the Sleep Subjective Quality (SSQ) scale, and the Hooper questionnaire was used to monitor participants' well-being status. Physical performance was assessed using the 5 m shuttle run test (5mSRT), which measured total distance (TD), best distance (BD), performance decrement (PD), fatigue index (FI), and the rating of perceived exertion (RPE). Affective valence was determined using the feeling scale (FS) and cognitive function was evaluated using the digit cancellation test (DCT). Recovery and muscle soreness perceptions were evaluated at multiple time points (pre-exercise, 5 min, 24 h, 48 h, and 72 h post-exercise) using the perceived recovery status (PRS) and the delayed onset muscle soreness (DOMS) scales, respectively. Results: During the supplementation, CrM improved sleep quality compared to PL, as measured with the SSQ scale (d = 0.81, p = 0.009), and was associated with an earlier in-bed time (r = 0.60; p = 0.026). However, CrM did not affect sleep latency (t = 0.98; p = 0.35), sleep efficiency (t = 0.018; p = 0.98), or total sleep time (t = 0.25; p = 0.81). After the supplementation phase, CrM resulted in significantly lower muscle soreness scores, as measured by the Hooper questionnaire (d = -0.59; p = 0.046), improved cognitive performance on the DCT (d = 0.77; p = 0.013), and enhanced TD (r = 0.88; p < 0.001) and BD (r = 0.76; p < 0.05) during the 5mSRT. However, CrM did not significantly affect other exercise-related measures such as RPE, fatigue index (FI), or performance decrement (PD) during the 5mSRT, nor did it alter other subjective recovery scales compared to PL, up to 72 h following the end of the supplementation phase (all p > 0.05). Conclusions: A 7-day CrM loading protocol improved subjective sleep quality during the supplementation phase, enhanced cognitive performance, and increased physical output during high-intensity intermittent exercise. CrM also reduced muscle soreness, but did not significantly affect objective sleep parameters, or recovery markers up to 72 h post-exercise. These findings suggest that CrM may offer additional benefits beyond its traditional ergogenic role. Trial Registration: This trial was registered on 18 September 2023 at the Pan African Clinical Trials Registry (PACT) (identifier: PACTR202309597156293).