How Does Sleep Affect Muscle Growth?

Micah Le'Gare
Oct 23 · 8 min read
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To reach new heights in fitness, it’s tempting to look outside ourselves for new answers. In search of new hacks we don’t realize there are things directly under our control that can propel results. For example take resistance training and muscle growth. We’ve all heard how rest and recovery is essential for growth, but most don’t know how sleep affects muscle growth specifically.

Sleep seems straight-forward; we close our eyes at night and BOOM- next thing we know it’s a new day. However thanks to science we’re learning that it has distinct stages and cycle that play into fitness. We’ve all heard how a good night’s rest is important for weightlifting and fitness as a whole. Though with all this new information about sleep coming out it’s natural to wonder — how does sleep affect muscle growth specifically?

While much is still unknown about sleep, I’ll do my best to describe the relationship between sleep and muscle growth.

Why Do We Sleep?

Interestingly all researchers agree there is no one physiological role sleep serves. Yet one dominant, over-arching purpose for sleep is to rejuvenate the body. Sleep is vital for development, energy conservation, brain waste clearance, immune health and much more, all of which is necessary for recovery. For the average lifter it directly provides muscle growth and mental alertness. However, regardless of training type, without adequate sleep, effort put into the gym is ultimately wasted.

Recharging The Brain

Immune Boost

Sleep And Muscle Strength

A cross sectional study performed on 10,000+ university students measured the association between sleep quality/duration and muscle strength. The study found that men who got 6 hours or less of sleep had poorer muscle strength than those who slept 7–8 hours or 8+hours(1).

There was also no real difference in results between those who slept 7–8 hours and those who slept 8 or more. It’s safe to assume that quality sleep is associated with greater muscle strength.

To me this is great news, but at the same time it opens even more questions. What about sleep lends itself not only to muscle growth but increased strength? What chemical/ biological processes happen while the mind is unconscious? Why do they only work well with certain amounts of rest and not when we’re awake?

So many questions, but we’ll try to break them down the best we can.

Why Sleep Is So Crucial For Muscle Growth

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I think a single word can describe the importance and necessity of sleep: BALANCE

The body burns hundreds of calories an hour simply standing. The brain burns a ridiculous amount of calories both conscious and unconscious to facilitate bodily function. Physically active individuals not only break down muscle fibers during exercise, but their metabolisms are constantly firing to keep up with the demand for energy.

To put it simply; there are a thousand and one systems at work within your body simultaneously. That means there are 1001 systems that need energy and maintenance while trying to support one another. When you look at it this way, you can see why recuperation seems impossible while the body is conscious and in constant motion.

This is where sleep comes in. While the body is still active during sleep, many of it’s systems aren’t stimulated to the same degree as when conscious. This allows the body to regain balance on a hormonal level, thus triggering repairs throughout the body.

Hormonal balance during sleep is the key to muscle growth and the reason why it’s absence leads to decreased muscle mass. Here are a few factors to remember that tie into muscle growth and quality sleep:

  • higher testosterone: getting the right amount of sleep increases the body’s levels of testosterone, which enhances its ability to build muscle.
  • Insulin-like growth factor 1 (IGF-1): adequate sleep boosts IGF-1 levels, enabling satellite cells to enter muscle fibers crucial for breaking strength and size limits.
  • lower cortisol: although cortisol is a necessary hormone, an abundance of it has been associated with the breakdown of muscle tissue. Reducing its presence in the bloodstream can help to increase muscle mass.
  • reduced inflammation: without the prevalence of chronic inflammation, the body can repair itself at a much quicker rate, including damaged muscle tissue from exercise.

Sleep’s Effect On Body Composition

In a study testing the effect of sleep protocol on resistance trained subjects, participants were split into two groups. The first was exercise and sleep optimization group, the second exercise only. Both groups performed resistance training twice a week for ten weeks, however the exercise/sleep optimization group was given education on how to improve sleep quality and quantity.

Fortunately both groups experienced gains in lean muscle mass. However the ExS group not only enjoyed slightly greater increases, they also reduced fat mass significantly (-1.8 kg +/- 0.8) while the exercise group did not (-0.8 kg +/- 1.0).

Controlling body composition is crucial for anyone looking to burn fat or build muscle. The fact that quality sleep can help in both processes highlights its importance in our everyday lives.

How Limited Sleep Affects Muscle Growth

With my pride out of the equation I realize that it’s ok to get a reasonable amount of sleep. And fortunately science backs up this notion.

Sleep is crucial for functioning on a systematic and cellular level, and it’s absence can have devastating effects. Reduced sleep can alter feeding patterns, glucose regulation, blood pressure, some hormonal axes, etc. With the hormonal changes comes a rise in cortisol and a decrease in testosterone and Growth Factor 1. It’s important to note those last 2 hormones are necessary for protein synthesis and as an extension muscle growth(2).

In short it’s theorized that a lack of sleep does 2 things:

  • reduces the activity of protein synthesis pathways
  • increases the activity of degradation pathways

Sleep deprivation alters the balance of anabolic and catabolic hormones creating a trend towards decreases in muscle protein synthesis.

Both of these lead to a loss of muscle mass all the while hindering muscle recovery for damaged tissue after exercise. I don’t know about you, but I’ll gladly get a few more hours of sleep if it means avoiding this outcome.

We’ve all heard it before, but there is a reason they say rest and recovery is just as important as training. At the end of the day the best exercise program, nutrition, or supplementation can’t compensate for lack of sleep.

Useful Sleep Tips For Muscle Growth

Casein Before Bed

Pre-sleep protein feeding at least 30 minutes before sleep has opened the door to great nutrient timing opportunities. This method has proven to increase resting metabolic rate, overnight muscle protein synthesis, and recovery(3).

Before you whip out your debit/credit card and rush to the nearest Vitamin Shoppe, it’s important to know what kind of protein works best.

Like the heading suggest, casein is your best option for overnight protein synthesis. Casein protein clots up the stomach delaying the gastric emptying process due to the acidic environment of the stomach. This results in a moderate release and increase of plasma amino acid concentration in the intestines.

All of this leads to prolonged overnight hyperaminoacidemia (that’s a mouthful) and serves as a precursor to overnight protein metabolism, thus increasing RMR.

Consuming a pre-sleep helping of at least 30g of casein can lead to improved resting metabolic rate, gym performance, and muscle gain over time.

Stick To A Consistent Sleep Schedule

Parents put their children to bed at a set time to ensure they get adequate rest in order to re-calibrate and grow. Us gym-goers need to follow suit.

Setting a specific window of time will guarantee your body gets enough rest through the night and grows properly.

Reduce Your Stress Levels

I would recommend setting aside an hour before bed to do things that put you at ease. A good book or soothing music can help get your mind off of daily troubles and focus it on positive subjects.

Improve The Quality Of Your Fitness

Having an effective, consistent workout regimen will help progressively build muscle AND ensure a good night’s rest. If you haven’t already I would prioritize finding a workout program that meets your hypertrophy goals and stick with it. With both adequate sleep and exercise grafted into your lifestyle I guarantee you’ll see an increase in results.

If you’ve made it this far I hope these tips will improve your sleep and quality sleep will improve your results as a whole.

Originally published at on October 23, 2020.

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In Fitness And In Health

Inspiring stories related to health, fitness and the pursuit of well-being.

Micah Le'Gare

Written by

I am a personal trainer, athlete, and nutrition specialist, but at the end of the day I’m just a guy who loves fitness. Just here to listen, learn, and help!

In Fitness And In Health

A fast-growing health and fitness community dedicated to sharing knowledge, lessons, and suggestions to living happier, healthier lives.

Micah Le'Gare

Written by

I am a personal trainer, athlete, and nutrition specialist, but at the end of the day I’m just a guy who loves fitness. Just here to listen, learn, and help!

In Fitness And In Health

A fast-growing health and fitness community dedicated to sharing knowledge, lessons, and suggestions to living happier, healthier lives.

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