By Andrea Hargraves 
- author, Emma Sweeney and Ian Walsh
- roll, Conversation*
When we ask ourselves what makes a great athlete, few people imagine that sleep can play an important role.
But many of the world’s best athletes claim sleep is an essential part of their training routine—and key to helping them perform.
Serena Williams, for example, strives to get eight hours of sleep every night. NBA star LeBron James aims to get eight to 10 hours of sleep, while football legend Tom Brady says he goes to bed earlier and sleeps at least nine hours.
No wonder, because sleep plays a major role in metabolism, tissue growth and repair (such as our muscles) and ensures that memory, reaction time and decision making function optimally. All of these processes affect athletic performance.
But it’s not just performance athletes that can benefit from an adequate night’s sleep.
Even amateur gym-goers can maximize the health and fitness benefits of working out by getting enough sleep each night.
Here are some of the ways sleep improves your fitness:
Aerobic energy
The exercise is great for improving aerobic fitness. It improves aerobic capacity (the ability to run or cycle faster with a heavier load) and efficiency (which means your body requires less oxygen to run or cycle at the same pace).
One factor that contributes to better aerobic capacity is the function of the body’s mitochondria.
Mitochondria are small structures within muscle cells that are responsible for generating the energy that muscles require during exercise.
Research shows that a lack of sleep (only four hours a night for five nights) can reduce mitochondrial function in healthy people.
High-intensity interval training has been shown to alleviate these deficiencies in the short term (over five days).
However, it is currently unclear how these impairments will affect long-term exercise adaptations.
So it’s best to get a good night’s sleep if one of your goals is to improve your aerobic capacity.
muscle growth
Sleep is also important if you want to build strength or muscle.
Muscle growth occurs when new proteins are added to the muscle structure – a process known as “muscle protein synthesis”.
This process is triggered by exercise and food intake (particularly protein) and can continue for at least 24 hours after training.
Serena Williams’ goal is to sleep eight hours a night
Research shows that even a few nights of inadequate sleep reduces the muscle protein synthesis response to nutrient intake.
This indicates that lack of sleep can make it more difficult for the body to gain muscle mass.
anabolic hormones;
Hormones act as chemical messengers that contribute to a range of functions throughout the body, such as tissue growth and development.
The hormones involved in these building processes can be called “anabolic” hormones.
Two anabolic hormones — testosterone and growth hormone, which are released during sleep — may also be important for recovery and adaptation to exercise.
These hormones play different roles in the body and are associated with better body composition (less fat, more muscle mass).
More muscle mass and less body fat can be beneficial for exercise and health.
When sleep is restricted to just five hours a night (the amount of sleep is comparable to that of many working adults), testosterone levels drop in healthy young men.
Restricting sleep for a similar duration also alters the release of growth hormone during sleep.
While more research is needed, there is a possibility that these hormones may play a role in mediating the relationship between sleep and physical fitness, given their connection to better body composition.
Refuel after your workout
Normally, exercise uses glucose (sugar) as a fuel source. Muscles store glucose from the food we eat in the form of glycogen to meet the demands of exercise.
Replenishing glycogen stores after exercise is an essential part of the recovery process. It can take up to 24 hours to fully replenish reserves with the right intake of nutrients.
The hormone insulin may be necessary for muscles to absorb glucose to produce glycogen.
A number of studies show that lack of sleep reduces the effectiveness of insulin.
This can affect the body’s ability to replenish glycogen stores. One study revealed a decrease in muscle glycogen stores after a night of sleep deprivation.
Low glycogen stores can impair post-workout performance in the short and long term, so it is important to ensure that glycogen stores are replenished post-workout.
How do you sleep well
Sleep is obviously important to physical fitness, so here are some ways to make sure you get a good night’s sleep:
- Develop a consistent bedtime routine: Do things before bed that help you relax and unwind — like reading a book or listening to relaxing music. Taking a warm bath before bed can also be beneficial, as the subsequent drop in body temperature can help you fall asleep faster.
- Create a good sleep environment: Exposure to light during the night can reduce sleep quality, so try to block out as much light as possible. Try to keep the room well ventilated, but not too cold. An environment that is too hot or too cold can interfere with sleep quality.
- Be physically active during the day: Research shows that physical activity is good for sleep quality, so try to include some exercise or physical activity in your day.
- Maintain a consistent sleep schedule: This will help regulate your sleep-wake cycle, which has been linked to improved sleep quality.
If you’re trying to improve your fitness, make sure you’re getting enough quality sleep — aim for at least seven to nine hours of sleep each night.
* Emma Sweeney is Professor of Exercise, Nutrition and Health at Nottingham Trent University in the UK.
Ian Walsh is Professor of Health and Exercise Science at Northumbria University in Newcastle, UK.
This article originally appeared on the academic news site The Conversation and is republished here under a Creative Commons license. Read the original version here (in English).