Everywhere it is written to "sleep well" to lose weight and build muscle.

I wonder what is the "correct" number of sleep hours? For Cardio workouts? Weight lifting?

If I'm doing a more intense workout (such as Crossfit) would I need more sleep hours?

1 Answer 1


In general, the people who live the longest, sleep six to seven hours per night see Wikipedia: Sleep.

So how does sleep and exercise relate to each other?

  • Ligtht physcial exercise seems to favor sleep, e.g. see Effects of light physcial exercise on sleep regulation in rats.

  • Heavy exercise and sleep deprivation creates an energy deficit, see this article where a group of soldiers did heavy, sustained work for 107 hours with only 2 hours of sleep. Even the group that was allowed to eat a lot (8000 kcal per day) lost around 1.3 kg of body fat. So exercising hard and not sleeping seems counterproductive to hard workouts.

  • Sleeping too much is not too good for you, see Physical Side Effects of Oversleeping. According to the article, sleeping for nine or 10 hours every night increases the chance of getting diabetes, becoming obese, getting headaches etc. However, in the context of training, some of the negative side effects (e.g. obesity) is unlikely.

So if you create a matrix of Sleep time {too little (less than 6-7 hours), right amount (6-7 hours), too much (9-10 hours)} and Exercise {no exercise, light exercise, heavy exercise} and map it too {+, -}, it seems reasonable that you should sleep 1-2 hours extra after a heavy workout.

My own experience is that I have sometimes difficulties to sleep after hard workouts late at the day. So the question might also be related to when at the day you exercise.

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