Post-Exercise Thermal Interventions and Nocturnal Sleep in Athletes: A Narrative Review of the Potential Underlying...

Sleep is essential for optimal performance and recovery in athletes. Post-exercise cold exposure, including cold water immersion and cryotherapy, is typically used to enhance recovery, but its effects on sleep remain unclear. Emerging evidence also suggests that post-exercise heat exposure, including sauna and hot water immersion before sleep may improve both objective and subjective sleep outcomes. However, the effectiveness of post-exercise thermal interventions for improving nocturnal sleep in athletes specifically has not yet been comprehensively evaluated. This narrative review synthesizes the current evidence and discusses the potential physiological mechanisms by which post-exercise thermal interventions may influence nocturnal sleep in athletes. Despite methodological heterogeneity, existing research indicates that post-exercise thermal interventions may influence the subsequent nocturnal sleep of athletes through multiple and varying interacting mechanisms. For example, cold exposure close to bedtime (< 2 h) may disrupt sleep by reducing the distal-to-proximal skin temperature gradient (DPG), thereby increasing sleep onset latency and shortening sleep duration. In contrast, when applied more than 2 h before bedtime, cold exposure may improve sleep by augmenting parasympathetic tone and/or reducing muscle soreness and associated nocturnal movement. Although it remains unclear whether post-exercise heat exposure improves sleep via autonomic modulation or reduced muscle soreness, existing evidence indicates that sleep may be facilitated by an increased DPG. Moderating factors such as sex, time of day, environmental temperature, bedding microclimate, acclimatization status, and training load may influence the effects of post-exercise thermal interventions on sleep and should be investigated in future studies.