Exercise and sleep: Why getting fit requires getting your ZZZs.

If you are serious about exercise, you take steps to maximize your workouts in order to meet your fitness goals. Obviously, what you do for exercise matters. You probably also appreciate that nutrition is important, so you pay attention to what you eat. But there is another important step to achieving your fitness goals you may not be aware of—sleep. This is the topic of my Health & Fitness column in the Aiken Standard this week.


Strenuous exercise can cause microscopic damage within muscles, which leads to inflammation and soreness. This sounds bad, but the damage is an important step in the muscle adapting to get bigger and stronger. Proper recovery is essential for the muscle to repair this damage through protein synthesis. Inadequate sleep decreases the activity of protein synthesis and increases the activity of protein breakdown, favoring the loss of muscle mass and interfering with muscle recovery after exercise. This is due to the balance between hormones that promote muscle growth and hormones that have an opposite effect on muscle.

Sleep is important because it provides a condition under which energy can be directed toward recovery rather than other activities. For example, muscles can rest to some extent when you are awake, but muscle activity falls to its lowest levels during sleep. The focus here is on muscle, but the brain that is also renewed by sleep. Since sensory input and activity are at their lowest during sleep, this is the time that protein synthesis in the brain is enhanced and growth and repair can occur.

The muscle damage that results from exercise, especially if it is strenuous, is necessary to promote muscle growth through protein synthesis. Exercise, particularly resistance training, stimulates the release of hormones important for protein synthesis. Some of these are further elevated at night, so sleep is an important time for adaptations related to muscle hypertrophy—bigger, stronger muscles—to occur. During the day there are high levels of hormones that inhibit protein synthesis. During sleep, these hormones decline and others, like growth hormone, stimulate protein synthesis.

Since the hormones that activate protein synthesis are most active after exercise and during sleep, eating protein before sleep is an effective strategy to enhance muscle mass and strength gains during resistance exercise training. This represents an important interaction between exercise, nutrition, and sleep, suggesting these factors work together to promote exercise adaptations. Since you can’t make up for poor sleep by doing an extra workout or eating more protein, you are wise to pay attention to all three!

Exercise has long been associated with improved sleep. This is thought to be due to that fact that exercise depletes energy stores and elevates body temperature and sleep restores energy, promotes tissue repair, and regulates body temperature. Activity, including exercise, during the day causes changes that promote sleep for the purpose of restoring a “normal” state overnight. For most people, daily exercise can help promote sleep, but you may need to determine the best time of day to work out. Exercise is a healthy, safe, inexpensive, and simple means of improving sleep, potentially replacing sleeping pills. Research also shows that aerobic exercise can improve sleep quality, mood, and feelings of vitality in people with chronic insomnia. 

Sleep is critical to good health and wellbeing as well as a key component in achieving your fitness goals. You probably already spend time tailoring your exercise sessions to meet your goals and make an effort to eat in a way that supports your training. Don’t forget that nutrition and training are most effective when you get enough sleep to maximize your adaptations. The bottom line is that when you are getting fit, make sure you get your ZZZs.

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