Sleep and Exercise

Feb 21, 2014

Fitness Handout

Did you know that getting enough zzzzzzs may actually improve your exercise performance? If you regularly cut sleep short, you may want to reconsider this practice.

Why is sleep so important for exercise, and what can you do to sleep longer and more deeply? Mike Bracko, EdD, FACSM, director of Dr. Bracko’s Fitness and of the Institute for Hockey Research, examines these questions.

Why Sleep Helps

During the night, we cycle through five stages of sleep. The stages include non–rapid eye movement (NREM) sleep (stages 1–4) and rapid eye movement (REM) sleep (stage 5).

Stage 3 and stage 4 are the important ones for exercise recovery. Stage 3 marks the beginning of deep sleep and is when human growth hormone (HGH) starts to be released. Stage 4, the deepest slow-wave sleep, helps to replenish physical and mental energy. During this stage, the body does most of its repair and regeneration work, thanks primarily to a continual release of HGH.

Because HGH is being released in stages 3 and 4, some fitness and sports performance trainers call sleep “the athlete’s steroid.” HGH helps maintain and repair muscles and cells, and it is key to improving athletic performance (McArdle, Katch & Katch 2009). As a result, you might argue that sleep is one key to fitness and sports performance. In reality, however, the key may lie in finding the correct balance of training, rest, nutrition and sleep.

How Long to Sleep?

How much sleep we need varies from person to person. Generally speaking, most adults need 7–9 hours of uninterrupted sleep per night (National Sleep Foundation 2013), while most adults get 6.5 per night. Many people think that decreasing their sleep to minimum tolerability is harmless and also efficient because they can get more done. However, sleep loss accumulates into sleep debt. Over a 5-day workweek, a nightly sleep loss of 90 minutes builds into a 7.5-hour sleep debt by the week- end. This equates to losing one full night of sleep during the workweek. Losing 2 hours of sleep a night (sleeping 6 hours instead of 8) significantly impairs performance, attention, working memory, long-term memory and decision making (Alhola & Polo-Kantola 2007).


Alhola, P., & Polo-Kantola, P. 2007. Sleep deprivation: Impact on cognitive performance, Neuropsychiatric Disease and Treatment, 3 (5), 553–67.

McArdle, W., Katch, F., & Katch, W. 2009. Exercise Physiology: Energy, Nutrition, and Human Performance. Baltimore: Lippincott, Williams, & Wilkens.

National Sleep Foundation. 2013. What happens when you sleep?; accessed Sept. 2013.

Rosekind, M. 2008. Peak performance requires optimal sleep and alertness. Olympic Coach, 20 (2), 4–7.

Fitness Journal, Volume 11, Issue 3

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