We all know that sleep is required both for our body and brain to function. However, despite our best efforts to have a good night’s sleep before a race, how often do we end up tossing and turning in bed, going to the loo every half an hour and waking up hours before our alarm is set. Pre-race nervousness, anxiety and excitement, jet lag, having to get up earlier to get to the start line, can all lead to a decrease in the quality and duration of sleep and it has been reported that even elite athletes report poor sleep prior to competition. I have recently run a half marathon where I had to attend a social obligation the night before and due to my son being unwell that same night I hardly got any sleep. I did ran though and I have to say that even though my time was not a PB, it was not that far off. I have seen people around me stress so much because they can’t sleep well the night before an important race, convincing themselves they can’t do well, that in the end they really don’t.
So what is the evidence out there to support whether sleeping badly the night before a race can affect our performance? As a PhD in Cell and Molecular Biology I decided to take a look at what the science has to tell us regarding sleep and athletic performance.
Sleep restriction vs sleep deprivation
Firstly we need to clarify one thing, the difference between sleep restriction and sleep deprivation. Sleep restriction (SR) means that one sleeps less hours than normal and there is a partial disturbance of the wake/sleep cycle. Sleep deprivation means that one does not sleep for a whole night or more. Of the two, sleep restriction is more relevant to athletes, as this is what we encounter usually pre-race.
- Sleep restriction (SR)
The effect of SR on performance outcome
Although conflicting data exists, on the whole, it appears that in subjects experiencing SR, studies show no effect on endurance/aerobic performance outcome (tests used included YoYo intermittent recovery test, cycling or running tests to exhaustion), while anaerobic ability (Wingate anaerobic test) seems to decline. So although you may be ok in a 10k race, perhaps your performance will be affected in short sprints. Mixed results exist regarding muscular strength, so no conclusion can be drawn there. Interestingly, athletic performance was affected in sports relying on high cognitive ability such as darts, tennis and handball but not in sports such as swimming, which involves gross motor execution (reviewed in Fullagar et al., 2015).
Physiological responses to SR
Effects of SR on cardiovascular/respiratory systems
Some studies using cycling tests have shown that SR leads to an increase in respiratory/cardiovascular parameters such as heart rate, minute ventilation and VO2 (oxygen uptake), while VO2max (maximal oxygen uptake) decreases. On the other hand, other studies have shown that VO2 (in a cycling protocol), peak heart rate (in a YoYo intermittent recovery test), VEmax (maximal minute ventilation), VT (tidal volume), VO2max (in a Wingate anaerobic test), FEV1 (forced expiratory volume; in a treadmill test to exhaustion) and lung function (in a swimming performance test) remain unaffected by SR. The discrepancies can be explained by the different exercise protocols used as well as by differences in the sensitivity of metabolic collection systems used (reviewed in Fullagar et al., 2015).
SR and cognitive performance
As previously mentioned, SR affects performance in sports with high cognitive reliance, so this perhaps is not pertinent to us runners. What is however relevant to us is that SR has been linked to poor mood states, depression, sleepiness, fatigue, increase in the perception of effort and confusion that can lead to overreaching and overtraining (Fullagar et al, 2015).
- Sleep deprivation (SD)
The effect of SD on performance outcome
Again, some data imply that SD may affect athletic performance, in particular walking and running to exhaustion. However, data that support the opposite also exist so one cannot be categorical one way or the other. Mixed data exist regarding anaerobic performance, ability to perform intermittent sprint tests and muscle strength, even when subjects have been awake for 36-60 hours (Fullagar et al., 2015; Vardar et al., 2007).
Physiological responses to SD
Effects of SR on cardiovascular/respiratory systems and cognitive behaviour
There appears to be a minimal effect on cardiorespiratory function in sleep-deprived athletes. Interestingly though, in one study testing the ability of 10 team-sport athletes to perform intermittent sprints after 30 hours of sleep deprivation, it was determined that sprint time as well as muscle glycogen stores were lower in the sleep deprived individuals (Skein et al., 2011). Inhibition of muscle glycogen restoration can be hugely important for us runners taking part in long distance events.
The effect of SD on cognitive behaviour has been established with many studies showing that sleep loss affects mood, liveliness and leads to increased fatigue, sleepiness and confusion. SD has been shown to increase anxiety levels in 13 physical education students without affecting anaerobic performance (Vardar et al., 2007). 30 hours of sleep deprivation negatively affected the profiles of mood states in team sport athletes performing sprint tests (Skein et al., 2011). A study of elite Brazilian volleyball athletes showed a correlation between sleep quality and confusion levels, while it was shown that athletes that slept well and won their games had lower stress levels (Andrade et al., 2016).
Looking into the subject of sleep loss and sports, in particular how sleep affects running performance whether this is sprinting, middle distance or long distance, it appears very little is known. Very few studies with small numbers of subjects taking part in each study have been conducted, making it difficult to draw conclusions. We need far more information on the effect of sleep loss on repeated bouts of exertion, a scenario that assimilates training sessions, information on performance during long running sessions (not just testing once off the time to exhaustion), information on the effects of sleep loss on elites as well as amateur athletes.
What comes out from the literature that exists up to date is that sleep restriction, a scenario that most athletes encounter the night before a race, does not appear to affect performance, nor does it have detrimental effects on the physiological factors tested. So as I suspected, if you don’t manage to sleep well the night before a race don’t panic. You will most probably be ok. You may have been better off if you have had 8 hours sleep, but even 5 hours can cut it to get you that long desired PB. The scientific evidence does not support the opposite by no means. What I would personally suggest is making sure you have slept well the days before the race so as to minimise the effect of that one night’s bad sleep.
Andrade A, Bevilacqua GG, Coimbra DR, Pereira FS, Brandt R. Sleep Quality, Mood and Performance: A Study of Elite Brazilian Volleyball Athletes. J Sports Sci Med. 2016; 15: 601-605.
Fullagar HH, Skorski S, Duffield R, Hammes D, Coutts AJ, Meyer T. Sleep and athletic performance: the effects of sleep loss on exercise performance, and physiological and cognitive responses to exercise. Sports Med. 2015; 45: 161-186.
Skein M, Duffield R, Edge J, Short MJ, Mündel T. Intermittent-sprint performance and muscle glycogen after 30 h of sleep deprivation. Med Sci Sports Exerc. 2011; 43: 1301-1311.
Vardar SA, Oztürk L, Kurt C, Bulut E, Sut N, Vardar E. Sleep deprivation induced anxiety and anaerobic performance. J Sports Sci Med. 2007; 6: 532-537.
Explanation of tests used in the studies mentioned
Wingate anaerobic test is usually done on a cycle ergometer and measures anaerobic power and capacity.
YoYo intermittent test evaluates the ability of a person to repeatedly perform intervals. A score is given according to the total distance covered until person cannot cover the distance at the time required.