How Does Sleep Affect Muscle Growth?

January 23, 2022

by Cathe Friedrich

Every night you lie down to sleep and hope that your slumber will be peaceful and pleasant. In fact, people spend one-third of their life in an unconscious state, but the time you spend in dreamland is vital for health and well-being. Lack of sleep is linked with numerous health risks, including mood changes, reduced reaction time, and difficulty focusing.

There are also physical health risks that lack of sleep increases the risk of. Studies show that a pattern of getting too little sleep is correlated with a higher risk of high blood pressure, heart disease, stroke, and type 2 diabetes. It also throws off your circadian rhythms, the natural cadences set by your internal biological clock. This throws off hormones and your sleep-wake cycle. Sleep is that important.

Unfortunately, many Americans don’t get enough sleep — the Centers for Disease Control and Prevention says about a third of U.S. adults report sleeping fewer than seven hours a night on average.

There’s an old proverb that sums up the implications of lack of sleep in a few words:

“Sleep is half of health”

— Bengali proverb

Keep that proverb in mind when you’re tempted to stay up late.

Sleep Matters if You Strength Train Too

Beyond health, getting enough sleep is important if you strength train and are trying to build muscle strength or size. With strength training, there’s a lot of emphasis on training technique and nutrition, and a lesser focus on other factors that contribute to strength training success, like stress management and sleep.

One reason sleep is so important is that your muscles repair during sleep. When you strength train, it creates micro-tears in the muscle fibers you worked, and your body must repair those tears. With repair, the muscle fibers increase in size and your muscles become larger over time. It’s during the deep stages of restful sleep that growth hormone occurs, a hormone that boosts muscle growth and promotes fat burning.

According to Sleep.org, most growth hormone release occurs during stage 3 of non-REM sleep, one of the deeper stages of sleep. If you don’t get enough sleep, you’ll get less growth hormone release and muscle repair, and hypertrophy will be negatively affected.

Lack of sleep places stress on your body, and that increases the release of cortisol, a stress hormone produced by the adrenal cortex, glands just above your kidneys. One problem with cortisol is it enhances muscle breakdown. That’s not what you want when you’re trying to build muscle. Cortisol interferes with all your hard work! It not only makes it harder to build muscle but also causes muscle breakdown and counteracts your hard work.

Cortisol negatively affects your body composition in other ways too. For example, higher levels change where your body stores fat. Rather than landing on your hips and thighs, it goes to your belly. You may have heard the term “stress belly.” This refers to tummy fat caused by stress and increased cortisol.

Sleep Makes You More Mentally Prepared to Train Too

Another downside of too little sleep is the effect it has on motivation and focus. Strength training requires pushing your muscles to perform a little harder over time. How will you put forth enough effort to grow your muscles when you’re fatigued from lack of sleep? Plus, fatigue increases the risk of training injuries.

Although no study has looked at strength training injuries specifically, a study involving teenage athletes found skimping on sleep boosted the odds of getting injured. In fact, teen athletes who slept less than 8 hours per night had a 68% higher risk of sustaining a sports injury. That’s something you want to avoid, no matter what type of training you do.

How Lack of Sleep Affects Muscle Strength

You might think that not sleeping enough would reduce the amount of force your muscles can generate. One study found that a single night of insufficient sleep didn’t diminish the amount of force muscles can generate, but several consecutive nights of too little sleep did. So, it’s not a productive pattern to get into if you’re trying to get stronger, leaner, and build more defined muscles.

The Bottom Line

High-quality sleep is an essential element of living, and it has many benefits for health and wellbeing. It can even have an impact on how your muscles grow in response to strength training. Most adults need between 7 and 9 hours of sleep per night. There is such a thing as getting too much sleep too.

Some studies show that people who sleep more than 9 hours per night are at higher risk of health problems and increased mortality. It’s unclear whether that’s cause of effect or whether people who sleep a lot already have health risks that cause them to sleep more.

The take-home message? Sleep isn’t only about recharging our batteries. There are profound consequences to lack of sleep. It affects your health, and it makes it harder to build muscle and maintain a healthy body composition. Make sure you’re getting your ZZZZs. You get your diet and exercise right but if you don’t give your body enough rest, you won’t maximize muscle growth or fitness gains.

If you have trouble sleeping, make sure you don’t have a medical problem, like sleep apnea, that’s interrupting your sleep. Look at your medications too and caffeine intake. Some medications can make it harder to sleep. Then work on sleep hygiene. Here are a few guidelines:

Turn off electronics and blue light releasing devices 2 hours before bedtime.
Take a hot bath 30 minutes before bedtime.
Add a source of white noise to your bedroom
Go to bed and wake up at the same time each day.
Make sure you have a comfy mattress and sheets
Remove clutter from your bedroom
Keep your bedroom temperature cool – no higher than 68 degrees F.

References:

Knowles OE, Drinkwater EJ, Urwin CS, Lamon S, Aisbett B. Inadequate sleep and muscle strength: Implications for resistance training. J Sci Med Sport. 2018 Sep;21(9):959-968. doi: 10.1016/j.jsams.2018.01.012. Epub 2018 Feb 2. PMID: 29422383.
“How Sleep Helps Your Muscles Recover and Grow | Sleep.org.” 11 Mar. 2021, sleep.org/how-sleep-adds-muscle/.
O’Donnell S, Beaven CM, Driller MW. From pillow to podium: a review on understanding sleep for elite athletes. Nat Sci Sleep. 2018 Aug 24;10:243-253. doi: 10.2147/NSS.S158598. PMID: 30197545; PMCID: PMC6112797.
“Cortisol and How It Affects Muscle Growth – AST Sports Science.” https://ast-ss.com/cortisol-and-how-it-affects-muscle-growth/.
“Effects of cortisol on muscle proteolysis and meat quality ….” 01 Nov. 2005, sciencedirect.com/science/article/pii/S030917400500207X.
gov. “1 in 3 adults don’t get enough sleep”

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