Sleep deprivation occurs when a person fails to meet their sleep needs, and can be acute or chronic, both of which negatively affect both health and performance (Taheri and Arabameri, 2012; Delmas, 2019). Total and partial sleep deprivation has been associated with slower reaction times, reduced muscle force output (Philip et al., 2003), concentration lapses (Degennaro et al., 2001), cognitive slowing and memory impairment (Himashree et al., 2002), as well as negatively impacting immunity and overall psychological wellbeing (Itani et al., 2017).
When chronic sleep deprivation occurs, it is commonly stage 2 and REM sleep that become proportionally decreased in response to restricted sleep time (Van Dongen et al., 2003), thus explaining the negative cognitive impacts seen following sleep deprivation. Greater slow wave activity (a measure of sleep propensity) in females has also been observed following sleep deprivation, potentially indicating differences in responses to sleep debt compared to males (Miles et al., 2022). The cumulative effect of physical and psychological performance reductions are likely to significantly affect sports performances.
Total sleep deprivation can be defined as a complete absence of sleep over a 24-hour period. Total sleep deprivation modifies inflammatory and hormonal responses to exercise-induced muscle damage. Leprout et al. (2011) demonstrated that partial sleep restriction, specifically going from 8 hours sleep per night to 5 hours sleep per night for one week, decreased testosterone levels by 15% in young men. This decrease negatively affects the ability to recover from exercise, specifically overnight muscle repair (Leprout et al., 2011), thus affecting future training potential and performance. In terms of strength performance, a systematic review of 17 studies concluded that sleep deprivation impairs maximal muscle strength in compound movements when performed without additional motivational strategies (Knowles et al., 2018).
However, the impact of sleep deprivation on anaerobic performance is less clear, with studies demonstrating sleep deprivation to have minimal impact on subsequent anaerobic performance (Taheri and Arabemiri, 2012), perhaps suggesting sleep deprivation does not affect the physiological mechanisms underpinning anaerobic capacity. This study by Taheri and Arabemiri (2012) used “strong verbal motivation” during the anaerobic test, which could account for lack of performance alterations between the sleep deprivation and controlled conditions, as Knowles et al. (2018) noted motivation could potentially override the physiological decrements of sleep deprivation on performance. Halson (2014) stated that the effects of sleep deprivation are task-specific, a statement that would appear to be supported by the wide-ranging results of studies in this area.
Whilst the aforementioned studies are of interest in describing the relationship between sleep and performance parameters, in reality few people are ever likely to experience total sleep deprivation, and perhaps even less likely to experience prolonged total sleep deprivation. A more common issue for many people however, is the experience of many acute bouts of partial sleep deprivation (Halson, 2014); partial sleep deprivation can be described as obtaining sleep less than the amount required to feel refreshed.
A small number of studies have examined partial sleep deprivation on athletic performance: Reilly and Deykin (1983) reported decrements in a range of psychomotor functions after one night of restricted sleep, where only 3 hours of sleep was permitted; however muscle strength and endurance performance were unaffected. It would seem that repeated bouts of exercise are affected to a greater degree by partial sleep deprivation than one-off, maximal efforts (Reilly and Hales, 1988; Reilly and Piercy, 1994; Reilly and Edwards, 2007). Interestingly, the work by Reilly and Piercy (1994) described greater impairments of performance later in the protocol, suggesting an accumulative effect of fatigue from sleep loss, which could be significant for coaches aiming to minimise performance loss following partial sleep deprivation. Sufrinko et al. (2016) found significant reductions in neurocognitive performance (visual memory tests and speed of response to a stimulus) were observed across over 7000 athletes who had sleep deprivation of less than 5 hours per night. Cullen et al. (2019) restricted participants to 4 hours sleep only, and found negative impairments on a countermovement jump and aerobic performance. The mechanism underpinning the performance reductions following partial sleep deprivation are unclear however, but Halson (2013) suggested perception of effort and pain tolerance to be key.
If sleep deprivation is anticipated, “sleep accumulation” or “sleep extension” is now recommended to offset the physiological degradation in performance, with the optimal sleep prolongation suggested to be 2 hours (Janušauskaitė et al., 2022). This strategy however, is described as an acute response to the anticipation of short term sleep deprivation, and now as a long-term solution to regularly obtaining insufficient sleep (Janušauskaitė et al., 2022). With Phillips et al. (2017) suggesting sleep regularity to be of key importance in the development of positive habitual sleep patterns, promoting improvements in both sleep quality and duration, it should be recognised that the use of sleep accumulation strategies in the long term would negatively impact sleep regularity. Therefore, the implementation of regular sleep routines is of greater value in long term sleep health.