How Does Sleep Improve Workouts?

If you've ever gone on a morning run or hit the gym after a poor night's sleep, you might have noticed a drop in your fitness.

Sleep and fitness are inherently linked. Sleep is the only time your body can devote maximum energy to repairing and healing muscles, regulating metabolism, and maintaining cardiovascular health with low blood pressure.

A lack of sleep undermines your body and exercise efforts, knocking your fitness out of sorts and making it hard to perform.

This article explores how sleep affects your fitness.

Let's jump in!

Physical Activity & Sleep: How Sleep Affects the Body

During sleep, your body enters a relaxed state where your sympathetic nervous system dials down and your muscles relax.

Total energy expenditure drops, and your pituitary gland releases growth hormone, which helps your body repair itself.

Many nocturnal processes, including growth hormone release and metabolism regulation, can't happen while awake. Sleep is intricately connected to hormonal and metabolic processes that affect fitness.

Sleep is also critical to energy modulation, with sleep impairment giving you less energy during the day. This will significantly reduce your performance during exercise and make you reach for sugar and caffeine to get through it.

Here's how sleep affects fitness in more detail:

Stunted muscle repair and regeneration

Sleep helps muscles release protein-building amino acids into the bloodstream and triggers the release of human growth hormone. Cellular regeneration increases, and your body creates new cells to repair and build.

Without sleep, you can't build or repair muscle effectively. Therefore, it takes longer to heal when you have broken/disrupted sleep.

Lower metabolism and energy levels

Sleep and Caffeine. How Does Sleep Improve Workouts?

Studies show that a lack of sleep diminishes the body's ability to convert fat into energy, which increases the risk of unwanted weight gain.

During sleep, your metabolism slows down by around 15%, a necessary process to balance energy reserves. Without this, your body can experience metabolic dysregulation, where it struggles to produce energy during the day.

Losing sleep reduces your total energy output, making it harder to beat your running times or personal best deadlift.

Lower immunity (getting sick more often)

You can't get in a good workout when you're poorly, so having a robust immune system is critical to maintaining fitness levels. Unfortunately, a lack of sleep is terrible for immunity, with sleep-deprived people more likely to get sick.

When we sleep, our immune system powers up, boosting cytokine production (associated with inflammation) and antibody release to fight disease.

Insufficient sleep makes you more likely to catch a common cold and upper respiratory tract infections – illnesses that will keep you away from the gym.

Common Cold, woman blowing her nose, covered with a blanket.

Reduced willpower and workout desire

Another way sleep affects fitness is by reducing your willpower. A lack of sleep reduces willpower, making it harder to drag yourself outside for a run or hit the gym. This can impact your fitness over the long term.

Thanks to research, we know our pre-frontal cortex (the part of your brain we use to exert willpower) is impaired with poor sleep, and it also reduces impulse control, making it hard to resist junk food and leading to bad dietary choices.

The bottom line on sleep and fitness

Science tells us that improving sleep duration and quality improves endurance and exercise performance. If you are serious about your fitness and health, getting better sleep is one of the best things you can do for better results.

Fitness, sleep, and mental health also have deep links, with more sleep and exercise known to improve anxiety and depression outcomes. If you are anxious or depressed, more sleep + exercise could be the answer.

Simply put, sleeping more, and exercising more, gives you double goodness. Look for ways to get more of each to supercharge your health.

If you enjoyed this article, read our strength training and sleep piece.