Why a good night's sleep is so important – especially before exercise

A few late nights can increase the risk of cardiac stress during exercise – and you're less likely to pick healthy foods to fuel up

Woman tired during exercise
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Why do we need to spend a third of our lives unconscious? Scientists have been puzzling over that particular fact for centuries. However, what we do know is that without adequate rest, our body and mind cannot function properly, especially for several nights on the trot. 

This is especially prevalent during exercise. If you use one of the best fitness watches or best fitness trackers, you'll be able to look back on all your data and cross-reference your nights of poor sleep with your workout performance, and we're willing to bet you're not hitting any PBs after just three or four hours of sleep. However, consecutive nights of poor sleep don't just result in bad workouts – it could mean your exercise induces more cardiac stress, damaging your heart. 

Research from Uppsala University studied participants who underwent an intense bout of exercise. One group did the exercise after a normal amount of sleep, and the others after three nights of 'curtailed' sleep. The research found higher levels of a protein known as troponin in the hearts of the participants who had less sleep. This protein is usually found in very high levels during cardiovascular events, such as heart attacks. 

Exercising is obviously good for your heart in a general sense, and a temporary lack of sleep is unlikely to do much long-term damage. However, chronic, long-term lack of sleep, or shift work, places undue pressure on the heart. 

Woman using her phone in bed

(Image credit: Getty Images)

Jonathan Cedernaes, associate professor at Uppsala University, writes that it's "possible that a more pronounced lack of sleep in the long run can increase the relative risk that the heart is injured in some way by more intense exercise."

Lack of sleep can also cause you to steer clear of the healthy whole grains, high-protein and high-fibre foods you should be using to fuel your workout, and instead opt for dopamine-inducing junk food. Research from the American Heart Association found poor sleep quality was associated with greater food intake and lower‐quality diet, which can increase cardiovascular disease risk. In addition, eating foods with a lower nutritional value will fuel your workouts much less effectively, as you won't have as much energy to give.

The solution? Better sleep. It's tough for many with conditions such as insomnia or even those who have to work shifts to get by, but take steps to improve the quality of your sleep when you can.

Meditation just before bed can relax the body and mind for better bedrest, while the old wives' tale of drinking a glass of milk before bed is actually true – milk contains tryptophan, an amino acid which can help you relax, produce serotonin and sleep better. Milk also contains casein, a slow-release protein found in our best protein powders for weight loss guide, which can help your body recover during the night. Our best diffusers for essential oils list can also help lull you to sleep with periodic spritzes of lavender.

Matt Evans

Matt Evans is an experienced health and fitness journalist and is currently Fitness and Wellbeing Editor at TechRadar, covering all things exercise and nutrition on Fit&Well's tech-focused sister site. Matt originally discovered exercise through martial arts: he holds a black belt in Karate and remains a keen runner, gym-goer, and infrequent yogi. His top fitness tip? Stretch.