A lack of sleep doesn鈥檛 just make it harder to motivate yourself to go out running; it also changes the way you move. Sleep-deprived runners don鈥檛 stiffen their leading leg as much before impact, which increases the time their feet are in contact with the ground and reduces the number of steps per minute.
鈥淵ou need to actively prepare your leg for ground contact,鈥� says at KU Leuven in Belgium. 鈥淲hen you鈥檙e sleep-deprived, you have less alertness, and you are less present in the moment. At least, that鈥檚 my hypothesis.鈥�
Previous studies have looked at how sleep deprivation affects running performance, the risk of injuries and physiological factors such as heart rate and oxygen consumption. But this is the first to look at how it affects the way people move, says Seynaeve.
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She and her colleagues had 11 women and 10 men each do two runs on a treadmill on different days, one week apart. The runs consisted of intervals of increasing intensity, with speeds based on an earlier test of each runner鈥檚 fitness.
Before one of the runs, the volunteers weren鈥檛 allowed to sleep at all, while they slept as normal before the other run. Their movements were monitored with a waist-mounted accelerometer and a motion-capture camera.
Running styles vary a lot between individuals, so the researchers didn鈥檛 find any changes distinctive enough to tell from a single run whether any random individual is sleep-deprived. However, for any one individual, they found significant changes between the two runs. When sleep-deprived, the runners took between 1 and 3 fewer steps per minute at the same speed, for instance.
Sleep deprivation also increased the time the runners鈥� feet were in contact with the ground, with more time known as grounded running. This may not sound like a bad thing. 鈥淧eople who have a lot of injuries are advised to run more grounded, because the load is reduced on their joints,鈥� says Seynaeve.
But other studies have found that a lack of sleep increases the risk of running injuries. For instance, a study last year found that runners who rated their sleep quality as poor were . Possibly this is a result of changed loads on different parts of the body, says Seynaeve. 鈥淲e see that, for example, the knee is loaded much more, so this could maybe lead to more knee injuries.鈥�
鈥淵es, if sleep deprivation changes how you move, that may be one way it could induce injury risk,鈥� says at the University of Arizona College of Medicine.
鈥淭his study is very well-designed and executed,鈥� says at the University of Denver, Colorado, who has looked at how running styles . There are some similarities, because both tiredness and sleep deprivation reduce cadence, but the two studies aren鈥檛 directly comparable, she says.
鈥淲hile this may have been outside the scope of this specific paper, I鈥檇 be interested in whether sleep deprivation might potentially exaggerate the effect of acute fatigue on running biomechanics,鈥� says Dimmick.
bioRxiv
