Sleep deprivation

Sleep your way to better performance

Nobody feels good after a bad night’s sleep. However, does sleep
loss affect physical performance? The early research suggested
that while it was detrimental to cognitive function, sleep loss didn’t
really have a significant effect on physical performance. However,
more recent research has indicated that sleep loss is detrimental
to endurance performance – for example, by increasing the
perceived exertion to maintain a given workload. Now a new
French study has looked at the combined effects of sleep
deprivation on both endurance performance and cognitive
In the study, twelve fit males underwent two testing
sessions. In one of these they had a normal night’s sleep and
in the other, they were deprived of sleep (ie very tired!). On the
first day, the subjects performed baseline cognitive and
neuromuscular testing (testing of the function and activity of
the muscles and the nerves that control them). After one
night’s sleep deprivation or normal sleep, the subjects
repeated the day 1 testing procedure and then performed a
40-minute sub-maximal cycling task and a much higher
intensity cycling test to exhaustion. Neuromuscular and
cognitive functions were evaluated during both the cycling
protocol and at task failure. The whole procedure was then
repeated with those subjects who had been sleep-deprived
having a normal night’s sleep and vice-versa. The researchers
then looked at the data to see a) what effects the sleep
deprivation had on physical and mental performance during
the cycling task and b) whether the neurological results
provided any insight into the mechanisms causing fatigue.
Unsurprisingly, perhaps, the sleep deprivation wasn’t great
for cycling performance; the rate of perceived exertion during
the sub-maximal ride was significantly higher and the time to
exhaustion on the more intense cycling session was less – the
cyclists managed an average of 20.6 minutes to exhaustion
after a normal night’s sleep but only 18.9 minutes when they
were sleep deprived. Also, some measures of muscle function
showed a drop of between 5 and 7% in performance and
response – however, there were no significant changes in
neuromuscular function. One interesting effect, however, was
that cycling seemed to help some measures of cognitive
function when the cyclists were in a sleep-deprived state. For
example, on the sleep deprived days, the cyclists’ reaction
times were 8% faster after the cycling task than they were
before the cycling. Likewise, they were better at completing
cognitive tasks in a sleep-deprived state and after the cycling
tests had taken place than before.
The first conclusion that can be drawn from this study is that
it provides further evidence that sleep deprivation is harmful to
endurance performance such as cycling (although the similar
neurological test results didn’t help the researchers identify the
precise mechanisms behind the fatigue). For those who are
competing/racing, a severe lack of sleep could seriously harm
your ability to keep on the pace. And even if your sport is
performed at a more leisurely pace, it’ll feel like harder work at
your normal training pace/riding speeds. Also of note is that if
you have had a really bad night’s sleep, a blast on the bike could
help you feel and perform better mentally afterwards. Overall,
though, if you have a big day on the bike looming, it’s almost
certainly worth trying to get the best night’s sleep you can
Med Sci Sports Exerc. 2013 Jun 10.

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