MODULE SLEEP
The impact on performance
Illness
Sir Dave Brailsford, the performance director of the successful British Cycling team between 2003-2014, understood the importance of staying healthy. In an attempt to avoid illness, he hired a surgeon to teach athletes how best to wash their hands (hand washing is an effective way to remove germs that make you sick). He also instructed his athletes to avoid shaking hands at competitions to reduce the chance of catching any last minute illnesses.
Sleep effects your immune system
During sleep, proteins such as cytokines, and antibodies are released to help fight infection (e.g. bacteria and viruses). However, with a lack of sleep the production of such proteins are reduced, preventing your immune system from functioning at its best, which makes it more likely that you will get ill.
Sleep helps you avoid the common cold
Cohen, Doyle, Alper, Janicki-Deverts, and Turner (2009) conducted a study where participants were intentionally exposed to a rhinovirus (a virus which is the predominant cause of a common cold) via a nasal drop. They wanted to learn whether differences in sleep duration and sleep quality would influence whether the participants got ill or not. I.e., does sleep provide any immunity against the common cold?
Firstly, the sleep patterns of 153 participants were monitored over 14 consecutive days, so an average sleep duration and sleep quality could be calculated for each participant. Then, they were subjected to the rhinovirus and monitored for a further 5 days to assess any signs of illness.
The researchers discovered that participants who had averaged less than 7 hours of sleep per night, were nearly 3 times more likely to develop a cold compared to those who had averaged 8 hours or more.
The quality of sleep also influenced whether a participant developed a cold. Participants who had less than 92% sleep efficiency (measured as the percentage of time a person is asleep from the time they lie down until the time they wake up the following morning), were 5.5 times more likely to develop a cold compared to those who had achieved at least 98% sleep efficiency.
The results suggest that poorer sleep preceding exposure to a virus, increases the chances of becoming ill. So athletes need to be aware of factors that may have a negative influence on their sleep.
Fatigue doesn't help
Fatigue is once such factor that is known to have a negative effect on sleep. Athletes spend hours training each week, and as a result can become fatigued from over-training. Over-training is characterised by an increase in intensity, duration, and/or frequency of training, which prevents an athlete from adequate recovery.
Hausswirth, Louis, Aubry, and Bonnet (2014) studied athletes over a 6-week period, and found that an increase in training volume had a negative effect on a person’s sleep quality, and made it more likely that an athlete would succumb to an infection, such as a common cold. The study included 27 participants, who were placed in a ‘normal’ training group or an ‘overloaded’ training group. Training sessions in the overloaded group were 30% longer in duration in comparison to the normal group.
At the completion of the study, participants were assigned to one of three groups. The overtrained group which showed declines in performance (suggesting this group was most effected by fatigue), the overtrained group which showed no decline in performance, and the normal training group. The prevalence of higher upper respiratory tract infections (e.g. cold) for each group was 67%, 22%, and 11% respectively, which support the theory that fatigue and lack of sleep increased the likelihood of getting ill.
The moral of the story
Illness is bad news for an athlete as it prevent them from being able to train and/or compete. It could make the difference between winning or losing. Ensure you follow the recommended amount of sleep has shown to reduce the onset of illnesses such as the common cold. Regardless of the effect it has on your performance, no one likes being ill anyway!
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References
Hausswirth, C., Louis, J., Aubry, A., & Bonnet, G. (2014). Evidence of disturbed sleep and increased illness in overreached endurance athletes. Medicine and Science in Sports and Exercise, 46 (5), 1036-45.