Sleep and the athlete: can daytime naps power performance?

In recent years, a large body of evidence has accumulated that getting enough sleep – and good quality sleep – is vital for sport and exercise performance. Ensure you get enough high-quality sleep and your performance is likely to be enhanced. However broken or insufficient sleep is not good for performance.

Why is sleep vital?

In terms of recovery, sleep is vital – not least because a number of hormonal responses take place in the lead up to and during sleep. One important hormone relating to athletic recovery is human growth hormone. Growth hormone is necessary for body restoration, and plays an important role in muscle growth and repair^(1,2) Muscle growth, repair, and bone building are vital for athletic recovery following strenuous training and competition; it has been reported that 95% of the daily production of growth hormone is released from the pituitary gland in the endocrine system during non-rapid eye movement sleep (NREM - ie deep sleep). Therefore deep or NREM sleep is considered the time in which the body actively repairs and restores itself^(3,4).

Given the above, it follows that a sleep shortage is likely to be counterproductive for athletic performance, and the research does indeed bear this out. Sleep deprivation is associated with higher rating of perceived effort (RPE) values for a given level of workload, potentially leading to reduced performance, particularly in endurance events^(5,6). In short, when an athlete is sleep deprived, he or she will experience greater levels of perceived effort to sustain a given workload compared to when sleep amounts have been adequate.

More night time sleep

Many athletes (just like non-athletes) experience times when sleep amounts are insufficient. This can easily happen after a single night of sleep deprivation - for example when going to bed very late but getting up at the normal time. However, probably more common is the scenario where athletes experience a succession of nights with not quite enough sleep – ie where a deficit accumulates over time. Typically this can happen during the working week, with the sleep deficit paid back over the weekend (ie lie-ins!).

A number of studies have looked at how abolishing a sleep deficit by ensuring extra sleep can benefit performance. However, almost all of these have investigated the benefits of extending the sleep time at night – ie going to bed earlier or sleeping in and getting up later⁽⁷⁾.

For example, a study by US scientists on 50 military athletes, researchers investigated the effects of four nights averaging an extra 80 minutes of sleep per night on subsequent performance in a range of mental and physical tests⁽⁸⁾. The results showed that compared to habitual sleep, adding extra sleep significantly improved performances in all the tests after their four nights’ of extra sleep. What was also noticeable was that performance in jumping capacity and levels of motivation remained elevated a further four days later - even when the athletes had resumed their normal sleep patterns. Similar benefits were observed in another study investigating exercise time to exhaustion following six nights where an extra 1.6 hours of sleep was added to the athletes’ normal night time sleep⁽⁹⁾.

What about daytime napping?

If more sleep at night can improve performance, especially when a sleep deficit exists, can daytime napping provide the same benefits? Up until recently, there was no consensus on this topic. However, with our growing understanding of the importance of sleep for athletic performance, more and more studies have started to appear in the literature, and they make for interesting reading.

A 2021 review study gathered together data from 37 previous studies on daytime ‘napping’ and physical performance⁽¹⁰⁾. While many of these studies were only ranked as ‘moderate quality’ (ie many lacked a control group, daytime nap lengths and timing were highly variable etc), the researchers concluded that napping is likely beneficial for physical and cognitive performance, perceptual measures, psychological state and night-time sleep. They also suggested that athletes should nap for 20 to 90 minutes, and between the hours of 1pm and 4pm. But they also stressed the importance of allowing at least 30 minutes after napping before physical activity is started (to get rid of any residual sleepiness from the nap!). Figure 1 sums up these recommendations.

Figure 1: The impact of napping on various measures of athletic performance⁽¹⁰⁾