Sports Coach Logo Sports Coach Training Principles Fitness Components


Link Between Fitness and Sleep

Jackie Kepler looks at the link between fitness and sleep, which you should not ignore.

Sleep has to be a full partner in any fitness/health plan. Because, as it turns out, sleep affects most of your body's systems, including appetite control, muscle strength, and the immune system. However, a staggering 28% to 44% of adults in the United States get less than the recommended seven to nine hours.

Here is how sleep impacts your fitness and how you can improve your sleep cycle.

Hunger and Food Cravings

Sleep deprivation is anytime you get less than seven hours of sleep, which causes the body to release more of the hunger hormone ghrelin. While you are dealing with extra hunger, the lack of sleep also causes less of the satiety hormone, leptin, to enter the bloodstream. Essentially, when you are tired, you are hungrier than usual, and it takes you longer to feel full.

But, the changes extend beyond hunger. When sleep-deprived, the brain receives higher "rewards" from high-fat, sugary foods, which intensifies cravings. Consequently, you are far more likely to reach for potato chips, cookies, and other unhealthy foods with high calories and more fat.

Muscle Strength and Recovery

More than your appetite changes when you are running without sleep. Muscle recovery, whether from daily use or intense workouts, takes place while you sleep but not until the deep sleep stages. It is here when the brain waves slow that the body releases human growth hormone (GH) and triggers muscle repair. A shortened or irregular sleep cycle limits the amount of time the muscles are exposed to GH and, consequently, slows recovery.

Along those same lines are the effects of sleep deprivation on muscle strength. As you may have guessed, without that adequate recovery time, muscle strength goes down, too. It does not matter whether you are maxing out or running on a treadmill; lack of sleep will slow you down.

Immune System Health

When you are feeling good, it is easy to stay on top of a healthy diet and exercise. But how many of us struggle once we are hit with a cold or, even worse, the flu? The immune system recharges itself and sends out antibodies to the lymph nodes while you sleep. If you find yourself sleep-deprived more often than not, you are more likely to get sick. Not only that, without adequate sleep, it takes longer to fight off infection because the immune system is not functioning at 100%.

You Can Improve Your Sleep

On the bright side, your sleep cycle is responsive to habits and behaviours, which means there is a lot you can do to improve the quality (and quantity) of your sleep.

  • Take Comfort Seriously: The comfort of your bed and the conditions in your bedroom can make or break your sleep. The mattress should support your weight and preferred sleep position. A cool, dark, quiet environment helps the body fall and stay asleep. Keep comfort items nearby like a weighted blanket or a cool glass of water, so you do not have to get out of bed during the night.
  • Be Predictable: Your body loves predictability, and the brain will alter your sleep cycle to accommodate your preferred schedule. By keeping a regular bedtime, you allow the brain to recognize when to release sleep hormones. You can further help this process by establishing a regular bedtime routine to give your brain some lead-in time to the actual start of the sleep cycle.
  • Eat Regularly Spaced and Times Meals: Meals should be healthy, but they should also be spaced at regular intervals and eaten around the same time each day. You can also help by eating foods that have nutrients used to make sleep hormones such as bananas, dairy products, sour cherries, and almonds.


Sleep, along with a healthy diet and regular exercise, supports an active lifestyle. Adequate sleep gives you the best possible chance of making and achieving all of your fitness goals. Move it up your priority list, and you will feel the difference after one night of high-quality sleep.

Page Reference

If you quote information from this page in your work, then the reference for this page is:

  • KEPLER, j. (2019) Link Between Fitness and Sleep [WWW] Available from: [Accessed

About the Author

Jackie Kepler is a sleep professional. She enjoys sleeping with her cats but sleeps on a king-size bed because she needs her space, too.