The Connection between Sleep & Muscle Growth

When you are deep in your fitness journey, it can feel frustrating, discouraging, and super disappointing when you plateau. A fitness plateau happens when you stop making progress, despite doing everything “right.” For example, you may stop getting stronger, losing weight, or toning up. If you are working on strength training and muscle growth, you may find that you can no longer increase your weights and stop noticing changes in your appearance.   

man making no progress working out

When you are sure your diet and workout routine are still top-notch, you need to evaluate your sleep quality. A lack of sleep is a common cause of a fitness or weight loss plateau as sleep is one of the most important (but often overlooked) factors contributing to your fitness goals and whether or not you reach them.    

When you aren’t sleeping enough, or your sleep quality is poor, it can cause you to gain weight which you can read more about in our blog post entitled The Studies Are In – Sleepless Nights Can Lead to Weight Gain.   But in addition to causing weight gain, sleep can affect muscle growth.

Athletes, weightlifters, and those with ambitious fitness goals must prioritize sleep. When you sleep, your body is able to repair and restore, contributing to growth and recovery. Your body also releases critical hormones needed for more significant gains.

A study published in the Journal of Musculoskeletal and Neuronal Interactions found the relationship between muscle size and sleep to be very important. The study consisted of over 10,000 university students between 16 and 30 years old. First, the strength of the students was tested using a handheld digital dynamometer, measuring handgrip. Then, their sleep quality and sleep duration were measured using a self-reported questionnaire. Upon collecting the data and adjusting for confounding factors, the researchers discovered a positive association between sleep quality and muscle strength. The men in the study who slept for less than six hours had less muscle strength than men who slept for seven to eight hours. Interestingly, the researchers found little difference in the female students. Yet, the researchers still concluded that “good sleep quality is associated with greater muscle strength, while short sleep duration may be a risk factor for decreased muscle strength in university students.”

man working out with ropes

Research has also revealed that poor sleep quality can reduce muscle mass. A 2011 study examined how sleep deprivation affected muscle gains by following individuals for 72 hours. The participants were split into two groups; one that slept for only 5.5 hours a night and another that slept for 8.5 hours a night. All individuals were put on the same calorie-regulated diet and workout routine, with the only difference being the amount of sleep they had over three days. The researchers discovered that those who slept for only 5.5 hours had 60% less muscle mass, and those who slept 8.5 hours had 40% more muscle mass.

The year before, in 2010, a study completed by the America College of Physicians looked at the same sleep quantities of 5.5 and 8.5 hours in addition to calorie deficits over two weeks. After two weeks, both groups had lost the same amount of fat; however, the group that only slept 5.5 hours had lost 60% more muscle, whereas the group that slept 8.5% preserved 60% more muscle.

studies about sleep and muscle growth

Another study compared the effects of 24-hour sleep loss on weightlifting performance with national-caliber male collegiate weightlifters. During the study, nine weightlifters completed 24-hours with no sleep, followed by a night of normal sleep. Their testosterone and cortisol levels were taken throughout, including mood levels and sleepiness. They then completed a resistance training protocol, and the researchers measured their performance. The researchers did not note a significant decrease in performance; however, a lack of sleep negatively impacted their mood and caused fatigue, sleepiness, and confusion. Although the researchers didn’t see a direct impact on performance, the decline in mood could adversely affect fitness goals in normal circumstances. According to Dr. Bert Jacobson, one’s emotional state affects athletic performance. You need to be motivated and have a positive mindset to get in that next rep, push your muscles to fatigue and even get yourself to the gym. When you haven’t had enough time on your millet pillow at night, you will be more inclined to skip the gym and hit the couch instead.  

Glycogen is another reason sleep affects muscle growth. Glucose is the only type of sugar your body can break down and use for energy. We ingest it through food, and then it is broken down and turned into glucose, which is stored and used for energy. The process of breaking down glucose and turning it into muscle glycogen occurs during sleep. Although glucose is also located in your blood and liver, muscle glycogen will produce more energy and is preferred for strenuous workouts and muscle building.

glucose breakdown process diagram

Nick Ebner, N.A.S.M. – C.P.T., P.I.C.P., told Men’s Journal that during sleep, our body is able to use the food we’ve eaten during the day to build muscle. In addition, when we sleep, growth hormone is released that improves regeneration and recovery.

While muscle glycogen will provide muscles with the energy to lift heavy, human growth hormone is critical for repair. Human growth hormone (HGH) is a naturally occurring hormone needed for cell reproduction, regeneration, and muscle growth. It helps maintain, build and repair muscles and healthy tissue, including the brain and vital organs. Studies have shown that poor sleep reduces the amount of HGH in your body. Therefore, you can enhance your HGH production by getting enough sleep, specifically deep sleep.

Sleep also affects testosterone levels. Testosterone is an anabolic hormone that plays a critical role in muscle growth. A 2015 paper found that when young men underwent a week of just 5 hours of sleep a night, their daily testosterone levels decreased by 10 to 15%! Despite its importance and how hard you push your body, sleep may be challenging. It isn’t uncommon for weightlifters to experience insomnia which negatively impacts their fitness goals. This can be caused by having caffeine or pre-workout too late in the day or scheduling your workouts close to bedtime. When you work out, you can activate stress-responsive systems that release adrenaline and cortisol, making it difficult to fall asleep. The longer your workout is, the longer you have been in an aroused state, and the longer it takes to come down from it. If possible, it is best to schedule workouts earlier in the day. Sleep experts generally recommend at least a few hours of wind-down time after a workout, to maximize the relationship between sleep and muscle growth.

testosterone levels in men by age comparison

To help you fall asleep, you can also take a natural sleep aid. Natural sleep aids that contain melatonin will tell your body it’s time for bed. Shawn Stevenson, an author and sleep expert, has described melatonin as the master switch that helps your body get the sleep, recovery, and rest it needs. The bright lights in the gym will inhibit melatonin production, so when you get home from a late-evening workout, take melatonin, and it will help you get the sleep you need.

Working out late at night can also leave you feeling hungry. This is because your body has used a lot of energy and will continue to use energy while you sleep to repair your muscles. To prevent yourself from waking up in the night from hunger, have something light that will also aid in muscle repair.

have a light protein packed salad before bed

In 2012, a study looked at the effect of eating protein before bed. In the study, 16 young, healthy males completed a weightlifting workout and then had 20 grams of protein immediately after. Later, half of the men were given a protein drink consisting of 40 grams of casein. The study revealed that protein synthesis rates increased in those who had the protein drink before bed, which increased post-exercise overnight recovery. A similar study had 44 men complete a 12-week resistance training program. Again, they were all put on a high-protein diet, but half the group received a protein drink before bed with 27.5 grams of protein, and the other half received a placebo drink. The group that had the protein drink had more significant improvements in muscle size, strength, and muscle fiber size.

Lastly, to ensure you don’t wake up from hunger, you need to get enough calories during the day. According to the U.S Department of Agriculture, a moderately active woman should have 2000 calories a day, and a moderately active man should have 2600 calories a day. Of course, if you are doing strenuous or multiple workouts a day, you will need more.

We’ve all heard the saying “no pain, no gain,” but when it comes to muscle growth, it’s a lack of sleep that will prevent gains. So if you are serious about muscle gains and your fitness goals, you need to prioritize the time you spend on your millet pillow at night. A strict diet and 5 AM workouts are great but are only effective if you are getting 8 hours of sleep at night! Sleep and Muscle Growth are as important as protein and recovery.

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