The Lived Experience of Paranoia: Systematic Review of Qualitative Studies.

Sleep and exercise exert reciprocal effects mediated by intricate, bidirectional interactions [,]. Experimental studies conducted in laboratory settings have demonstrated that acute sleep deprivation, whether total [] or partial [], has a detrimental effect on aerobic exercise performance []. This deleterious effect appears to occur notably through an alteration in the perception of effort, particularly by increasing perceived exertion [,]. Conversely, promoting sleep, especially over multiple days, has been shown to enhance endurance performance in improving perceived exertion and attention [,]. Aerobic physical exercise is well known to exert a substantial influence on sleep [,]. Acute modifications are typically observed, including increases in total sleep duration [, , , , , ] and in the proportion of deep sleep stages, such as slow-wave (SW) [, , , , , ] and a decrease of paradoxical (rapid-eye-movement (REM)) sleep [, , ,,]. However, findings across studies remain heterogeneous, likely due to exercise-related factors such as the duration [,,, , ] and intensity [, , , , ]. Individual characteristics, including age [,,] and athletic level [,,, , ] may also modulate these effects. Considering outdoor activities, the number of trail and ultra-race races has grown rapidly over the past decade [], offering a wide range of distances and elevation profiles from short trail races ranging from 21 to 41 km to ultra-trail races over 42 km. These outdoor events also often extend over several days, adding the additional challenge of sleep deprivation to the inherent demands of endurance running and environmental constraints, including hypoxia and exposure to heat and/or cold [,]. All these constraints inevitably lead to changes in sleep following this type of event. In an early study on a small sample, Shapiro et al. (1981) observed major changes in sleep SW and REM sleep durations after an ultra-trail road race in six highly fit athletes on four successive polysomnographic nights after completing a 92-km road race []. Interestingly, these recordings reveal an increased wake duration after the trial. However, the origin of this wakefulness remains unidentified. One way to understand the sleep changes that follow an ultra-trail event is by considering the homeostatic dimension of sleep [], namely the increase in sleep pressure that can be caused by sleep deprivation [,], heat exposure [] and hypoxia [], and the physical demands of endurance exercise []. More modestly, the circadian process may also contribute depending on the race start time and its duration []. However, the homeostatic or circadian processes alone may not fully account for post-race sleep alterations. A long wake after sleep onset (WASO) raises the question of arousal process [, , ] due to ultra-endurance exercise. All these constraints and the stress they generate can also disrupt sleep continuity, promoting fragmented and less restorative sleep than would be necessary []. An integrative framework therefore could consider the interaction between homeostatic sleep pressure, circadian processes regulating the timing of sleep and wakefulness [], and arousal-related process, which encompass exercise-induced physiological stressors that can destabilize sleep [,]. These processes may act in opposing directions and could help explain why an increased need for sleep after ultra-endurance events does not necessarily translate into long and continuous sleep.