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Effects of exercising with a lack of sleep

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Effects of exercising with a lack of sleep


August 2019


Most adults, on average, need between 7-9 hours sleep a night. Sleep is important to allow your body to rest and recover, and replenish its energy levels.

Lack of sleep can negatively affect your training: you will feel less energised and less motivated, meaning you may not even make it to the gym, and if you do you won’t perform to your full potential. A lack of sleep can also affect your concentration and fog your memory, which will make it harder to get your workout done. You are at higher risk of injury when you exercise with sleep deprivation as your reaction times will be slower and your judgement will be clouded by fatigue.

A consistent lack of sleep could cause you to gain weight – the opposite of your goals if you’re trying to lose weight or maintain. Studies have shown a lack of sleep causes a decrease in leptin, a hormone that is responsible for making you feel full. On top of that, a lack of sleep also increases the body’s levels of ghrelin, which will in turn increase your appetite. Your appetite can also be increased by an increase in cortisol levels that could be caused by lack of sleep. Cortisol is the stress hormone, and high levels can also cause a weakened immune system, high blood pressure, cholesterol, lower bone density and heart disease. 

Sleep is important to allow your body to rest and recover, and so a lack of sleep will inhibit your recovery. Your muscles will take longer to recover from your last workout, therefore you’ll likely feel sorer for longer. So if you know you’re lacking sleep recently, maybe skip that workout and swap it for a few extra hours kip. You’ll feel a lot better during your workout if you are fully rested!