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Sleep and Muscle Growth

muscle recovery sleep studies Nov 13, 2019

Sleep and Muscle Growth

Luke Tulloch

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According to studies, sleep is a sure-fire path to building more muscle and preventing muscle loss during a diet. It enhances recovery and improves performance in the gym. Read on to find out how much sleep is enough, whether using naps is a good idea and whether interrupted sleep is a problem.

In fact, this is why focusing on sleep took the top 2 tips for general health in my recent blog post.


Does sleep affect muscle growth?


Let’s first answer the basic premise. If you’ve read my previous article on training volume, you’d know how important it is that you recover well from training. Poorer recovery leads to lower weekly training volume which leads to slower gains in strength and muscle.

Muscle growth is highly dependent on adequate gym performance. Since we’re trying to induce adaptation (muscle growth) with a stimulus (lifting weights), it’s important that the magnitude of that stimulus is consistently high enough to promote muscle growth over time. Ideally, we want to line up multiple muscle-boosting gym sessions over several weeks and months to maximise muscle growth.

Another oft-missed factor in your long-term progress is illness. If you get sick you can’t train, and if you can’t train you aren’t going to grow. Sleep directly affects the effectiveness of your immune system.

Here’s where sleep plays another important role: lack of sleep affects athletic performance.


How does sleep affect training?


The research has looked at some specific areas of training. Based on current evidence, it looks like missing an hour or two of sleep doesn’t have massive effects on single bouts of aerobic exercise and maximal strength. These are minimally affected.

However, everything else does suffer. Sports-specific skill execution (hand/eye coordination, agility, decision-making during play), submaximal sustained exercise bouts (meaning anything less than very heavy sets), and muscular/anaerobic power are substantially impaired.

Effect of time of day and partial sleep deprivation on short-term, high-power output.


In this study, power output was measured using a Wingate test, and it was substantially reduced after one night where participants were woken after 4 hours of sleep.

Wingate tests are a commonly used measurement of maximum anaerobic output, and are very tough.



Effects of time-of-day and partial sleep deprivation on short-term maximal performances of judo competitors.

 In this study, Judo competitors were also woken after 4 hours of sleep and had several measurements of physical performance taken, including maximal voluntary contraction, handgrip, and Wingate tests.

So, even one poor night of sleep can have a big impact – we’re not necessarily only talking about habitual sleep deprivation here!

This means the training stimulus we’re using to try and make our muscle grow is impacted by a lack of sleep.

Aside from anything else, your subjective feelings of fatigue are higher. If I were a betting man, I’d say that it’s pretty unlikely you’re going to have a killer session when it took you 3 snoozes to get out of bed that morning.


So far, we’ve established that sleep definitely does affect how much muscle and strength you can build!

Why? It hinders recovery from training, increases fatigue and lowers the muscle output – meaning less work gets done that could be contributing to muscle growth.


But can you lose muscle from not enough sleep?


Lack of sleep and muscle loss


In one study, subjects were put into a calorie deficit. Participants spent two 14-day periods in the laboratory with scheduled time-in-bed of either 8.5 or 5.5 hours per night. They had DEXA scans taken to measure their muscle mass and body fat before and after the experimental period.

Insufficient sleep undermines dietary efforts to reduce adiposity

The subjects lost 60% more lean mass and 55% less body fat during a two-week diet while sleeping for 5.5 hours per night compared to sleeping 8.5 hours a night!

These subjects weren’t weight training and it’s unlikely they had high protein intakes, but the results are hardly splitting hairs.

Another aspect that many people fail to consider is that sleep has flow-on effects on diet quality. We tend to be more susceptible to hunger and make poorer dietary choices when sleep-deprived, which makes dieting that much harder.


Another study looking at sleep and muscle loss

A more recent study used a less drastic difference in sleep duration with similar outcomes. This study went for 8 weeks and subjects were split into two groups. One group used a caloric deficit only and the other had a caloric deficit plus sleep restriction of about an hour a day.

Influence of sleep restriction on weight loss outcomes associated with caloric restriction.

One cool feature of this study design was that the researchers only restricted sleep for 5 days a week. They let the sleep restriction group sleep in as much as they liked for 2 days a week – this probably mirrors what most of us do on the weekend.

Despite this, they found that even though both groups lost the same amount of weight, the sleep restricted group lost less fat and more lean mass.



To quote the authors: “Approximately 1 hr of sleep restriction on five nights a week led to less proportion of fat mass loss in individuals undergoing hypocaloric weight loss, despite similar weight loss. SR may adversely affect changes in body composition and "catch-up" sleep may not completely reverse it.”

Therefore, if you’re in a calorie deficit it’s definitely advisable to focus on sleep to limit muscle loss and maximise fat loss.


Naps and muscle growth


Most studies look at total sleep duration, favouring continuous time spent in bed asleep. This doesn’t mean naps can’t be helpful, though.

Effect of different nap opportunity durations on short-term maximal performance, attention, feelings, muscle soreness, fatigue, stress and sleep.


So far this is the most complete study examining different nap durations and the effects on both cognitive and physical performance. It also measured subjective ratings of muscle soreness, mood, fatigue, stress, and sleep quality.

Four different conditions were used. The control group used no naps, and the three other groups had 25-, 35-, and 45-minute nap opportunities respectively (a nap opportunity means subjects had a window of time to nap, but the researchers didn’t measure how long they actually spent asleep).

In short, there was a graded response across conditions. The more time allowed for napping, the better subjects did in every parameter tested. Their jumping performance increased, their cognitive task performance increased and their subjective feelings of everything else also improved.

The biggest downside to napping during the day is pointed out in the same systematic review I’ve been referencing with regards to athletic performance. The authors make a good point that napping might be beneficial for some people, but for others it can disrupt the ability to fall asleep easily later that night. This should be major consideration if you’re looking at introducing naps – try and nap early enough in the day that it won’t affect your regular sleep schedule.

With this in mind, naps are most useful for people who can’t get adequate sleep at night. If you’re already getting the recommended amount, naps might not be that helpful to you and could run the risk of impacting your night-time sleep quality.


How much sleep do bodybuilders get? From an anecdotal perspective – I have memories of watching the best bodybuilders from the 90s and 2000s and almost to a man, they all seemed to nap during the day!


Is 6 hours of sleep enough to build muscle?


To summarize the current literature, it seems that trying to hit between 7 and 9 hours of continuous sleep each night is best. Try to maintain a regular sleep schedule as much as possible.

If you’re a competitive athlete, getting more sleep seems likely to improve performance, but remember that most research has been done in collegiate-level athletes who have a pretty high training load on top of having to study, so the benefits of sleeping more than 7-9 hours may not apply to those of us spending less time training.

If you happen to miss out on sleep for whatever reason, napping can be a helpful way to try and top up a sleep deficit but is unlikely to come out ahead of continuous, uninterrupted sleep even if total daily duration is equal.



Look out for a future article on the best methods to improve sleep duration and quality. Sign up to the newsletter to hear more.

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