Most of the literature on sleep is regarding restriction and its impact on health and performance. However, there is a growing body of research on sleep extension and the potential implications it may have on athletic performance in particular. It’s fairly well understood that sleep is a primary contributor to recovery and performance. In spite of this, it’s estimated over ⅓ of the american population is underslept (1). The American Academy Of Sleep Medicine recommends individuals aged 18-60 sleep a minimum of seven hours a day (1). Failing to meet this requirement has been associated with various chronic conditions such as heart disease, stroke, diabetes, high blood pressure, along with various other deleterious health and performance outcomes.
One paper looking at the effects of sleep deprivation on resistance training performance found significant reductions in strength in bench press, deadlift, and leg press. Additionally the researchers observed increased subjective feelings of difficulty, and increased sleepiness scores (2). Reductions in strength were preserved until the fourth consecutive night of sleep restriction, but mood, fatigue and other subjective qualities of sleep deprivation increased after just one night of nocturnal sleep restriction.
A study looking at the cardiovascular, respiratory and metabolic responses to sleep restriction in endurance trained athletes found “After partial sleep deprivation, there were statistically significant increases in heart rate (P less than 0.05) and ventilation (P less than 0.05) at submaximal exercise compared with results obtained after the baseline night. Both variables were also significantly enhanced at maximal exercise, while the peak oxygen consumption (VO2) dropped (P less than 0.05) even though the maximal sustained exercise intensity was not different” (3).
Sleep restriction reduces alertness, coordination and other psychomotor characteristics as was found in a 2009 paper by Edwards et al. whereby participants in the sleep restricted group saw an associative decrease in performance of throwing darts (4). Sleep is known to play an important role in cognitive restitution, and research has consistently found impeded attentional mechanisms such as reaction time and coordination when sleep is restricted (5). Sleep restriction of varying degrees has also been shown to augment the time course to return to baseline performance (6). With chronic sleep restriction having a longer refractory period than acute restriction before returning to baseline.
One paper looking at the affects of sleep restriction on sprint performance and muscle glycogen content found “Sleep loss and associated reductions in muscle glycogen and perceptual stress reduced sprint performance and slowed pacing strategies during intermittent-sprint exercise for male team-sport athletes” (7). Various other studies have demonstrated a strong association between sleep deprivation and reduced muscular performance (8) (9). There also appears to be considerable inter-individual differences in resilience with regard to sleep deprivation. With some individuals experiencing greater performance dropoff than others under similar conditions (10).
Also relevant but maybe less obvious is the role of body composition in performance. This is likely more relevant to sports where weight classes exist and where power to weight ratios are critical determinants of performance. Sleep deprivation has been shown to have significant deleterious results on body composition with one study finding “Sleep curtailment decreased the proportion of weight lost as fat by 55% (1.4 vs. 0.6 kg with 8.5 vs. 5.5 hours of sleep opportunity, respectively; P = 0.043) and increased the loss of fat-free body mass by 60% (1.5 vs. 2.4 kg; P = 0.002). This was accompanied by markers of enhanced neuroendocrine adaptation to caloric restriction, increased hunger, and a shift in relative substrate utilization toward oxidation of less fat” (11). Thus poor sleep can have an unfavourable impact on your body composition.
So, now that we’ve covered several of the potential consequences of sleep restriction let’s shift gears and discuss the antithesis. A 2011 paper aimed to investigate the effects of sleep extension on various metrics of athletic performance and other cognitive measurements. The researchers found “Total objective nightly sleep time increased during sleep extension compared to baseline by 110.9 ± 79.7 min (P < 0.001). Subjects demonstrated a faster timed sprint following sleep extension (16.2 ± 0.61 sec at baseline vs. 15.5 ± 0.54 sec at end of sleep extension, P < 0.001). Shooting accuracy improved, with free throw percentage increasing by 9% and 3-point field goal percentage increasing by 9.2% (P < 0.001). Mean PVT reaction time and Epworth Sleepiness Scale scores decreased following sleep extension (P < 0.01). POMS scores improved with increased vigor and decreased fatigue subscales (P < 0.001). Subjects also reported improved overall ratings of physical and mental well-being during practices and games” (12).
As you can see there were significant increases in performance from baseline. Subjects initially were sleeping between 6-9 hours per night, but during the intervention were instructed to record a minimum of 10 hours in bed each night. It’s important to note that 10hr time in bed is not the same as 10hr of sleep. Due to obvious limitations the objective of the study was to measure time in bed which was in this case a decent proxy for total sleep. However, it may not always be practical to adopt a 10hr nocturnal sleeping schedule. A bi-phasic (2 phases) or polyphasic (3+ phases) approach to sleep is characterized by a fragmented sleep pattern. This approach has demonstrated beneficial effects in subjects with sleep disorders (13).
Napping has also been shown to meaningfully improve cognitive performance (14) (15). Since total cumulative sleep throughout the day is a reasonable metric for recovery and athletic performance. Utilizing naps can be an effective strategy to bolster total sleep, enhance recovery and athletic performance if extending nocturnal sleep is not a practical option. One study found just a 10 minute nap was enough to significantly improve alertness, and cognitive performance (16). Longer naps of +30 minutes also have been shown to have significant benefit. However, longer naps may lead to a phenomena called sleep inertia. Essentially this is a period of cognitive impairment following arising from a longer duration nap (+30 minutes) (16). Sleep inertia does not persist throughout the day but it may be beneficial to structure longer naps away from cognitively demanding tasks (ie. work, training etc.).
An additional resource to enhance the quality of your sleep is outlined by the national institute of health.
In summation, there does appear to be good evidence of the performance enhancing effects of sleep extension up to 10 hours per night. However, the benefit it confers may vary since recovery requirements are individual in nature. Good luck!