What happens to your body while you sleep?
Sleep runs in cycles of lighter sleep, deep (slow-wave) sleep and REM sleep. Each does a different job.
Deep sleep is the physical repair shift. In adult men, much of the day's growth hormone is released during slow-wave sleep, and growth hormone drives tissue repair and protein synthesis. REM sleep is more about the brain: memory, learning and the motor skills you practised that day.
The largest pulses of growth hormone secretion in healthy men occur shortly after sleep onset, closely linked to slow-wave sleep.
Source: Van Cauter E, Plat L (1996). Journal of Pediatrics.What does short sleep cost an athlete?
A review of sleep and athletic performance found sleep loss hurts endurance, prolonged and repeated efforts most, along with reaction time, mood and decision-making. Effort feels harder, motivation drops, and the risk of mistakes rises.
After one week of sleeping 5 hours a night, healthy young men had 10–15% lower daytime testosterone levels.
Source: Leproult R, Van Cauter E (2011). JAMA.Testosterone and growth hormone are central to building and repairing muscle. Cutting sleep cuts into both.
What happens when athletes sleep more?
College basketball players aimed for 10 hours in bed each night for 5–7 weeks. Their sprint times got faster, free-throw and three-point shooting accuracy each improved by about 9%, and they reported better mood and less fatigue. Sleep was the only thing changed.
Source: Mah CD et al. (2011). Sleep.It was a small study, but the message has been repeated across sport: many athletes carry a sleep debt they do not realise, and paying it back shows up on the scoreboard.
The best recovery tool costs nothing. It only asks you to switch off.
GritxLabs Editorial Team
A simple sleep protocol for better recovery
Extra tips for athletes
- Late games and sessions raise heart rate and alertness. Build a 30–60 minute wind-down: shower, light snack, low light.
- Travel and early starts eat into sleep. Bank extra sleep in the nights before.
- Food matters too. A balanced dinner, not too heavy and not too late, helps. Sports nutrition reviews also point to protein and some carbohydrate in the evening as reasonable choices.
- Track how you feel, not just the hours. Waking refreshed is the real test.
What we are working on
Sleep is the foundation of everything we make, which is why GRIT. Sleep is in development: an effervescent tablet you drop in water before bed. We will share the full formula and the research behind it at launch. No added sugar and 100% vegetarian, like every GRIT. product.
What this means for you
- Aim for 7–9 hours, and more in heavy training blocks.
- Protect deep sleep with consistent times, a caffeine curfew and a dark, cool room.
- Treat sleep as training. It is where the adaptations happen.
Frequently asked questions
How much sleep do athletes need?
Adults need 7–9 hours. Many athletes benefit from more, especially in heavy training, and studies of sleep extension show performance gains.
Does sleep help muscle recovery?
Yes. Much of the body's growth hormone is released during deep sleep, and sleep loss lowers testosterone, both of which matter for repair.
Are naps good for athletes?
Short naps of about 20–30 minutes in the early afternoon can help after a short night, without disturbing the next night's sleep.
Does using my phone before bed affect sleep?
Yes. In one study, reading on a light-emitting device before bed delayed melatonin, made it harder to fall asleep and reduced next-morning alertness.
References
- Van Cauter E, Plat L (1996). Physiology of growth hormone secretion during sleep. Journal of Pediatrics, 128(5 Pt 2), S32–S37.
- Fullagar HHK et al. (2015). Sleep and athletic performance: the effects of sleep loss on exercise performance, and physiological and cognitive responses to exercise. Sports Medicine, 45(2), 161–186.
- Leproult R, Van Cauter E (2011). Effect of 1 week of sleep restriction on testosterone levels in young healthy men. JAMA, 305(21), 2173–2174.
- Mah CD et al. (2011). The effects of sleep extension on the athletic performance of collegiate basketball players. Sleep, 34(7), 943–950.
- Hirshkowitz M et al. (2015). National Sleep Foundation's sleep time duration recommendations: methodology and results summary. Sleep Health, 1(1), 40–43.
- Chang AM et al. (2015). Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. PNAS, 112(4), 1232–1237.
- Halson SL (2014). Sleep in elite athletes and nutritional interventions to enhance sleep. Sports Medicine, 44(Suppl 1), S13–S23.
This article is for general education and is not medical advice. Talk to a doctor or registered dietitian before changing your diet or supplements, especially if you are pregnant, nursing, under 18, taking medication or have a health condition.