Sleep in endurance sports – Part 1: Sleep duration and phases

We start today’s #ScienceFriday with our new series: Regeneration in sports by sleep. In the coming weeks, we will summarise the most important information on the topic briefly and concisely. 


„Not simply the absence of waking, sleep is a special activity of the brain, controlled by an elaborate and precise mechanism.“
„Not simply a state of rest, sleep has its own specific, positive functions.“

  • A distinction is made between rapid eye movement (REM) and non-REM stages 1-3 (NREM).
  • NREM sleep is divided into three stages and is associated with a progressive increase in sleep depth (Carskadon & Dement, 2011).

Sleep duration

Source: National Sleep Foundation (https://www.sleepfoundation.org/articles/how-much-sleep-do-we-really-need)

NREM-Phase 1

  • Start of the sleep cycle
  • Transition period between wakefulness and sleep
  • Light sleep phase
  • Duration: 5-10 minutes

NREM-Phase 2

  • People become less aware of their surroundings
  • Body temperature decreases by 0.4 – 1.0 degrees Celsius (1)
  • Breathing and heart rate become more regular
  • Duration: 20 minutes (2)

NREM-Phase 3

  • Muscles relax
  • drop in blood pressure and respiratory rate
  • Deepest sleep occurs (3)
  • Distribution of growth hormones (4)
  • Healing of micro-damages is accelerated


  • The brain becomes more active
  • The body is relaxed and immobilised
  • You start to dream
  • The eyes move fast
  • Muscular atony (lack of normal muscle tone)

Contemporary studies

  • Optimal conditions for anabolism (5)
  • A valuable resource for psychological and physiological well-being (6)
  • More deep sleep means increased regeneration
  • In the middle of the night, the melatonin release reaches its maximum
  • Melatonin: antioxidant and radical scavenging capacity → Cell repair (7)


  1. Murphy, P. J., & Campbell, S. S. (1997). Nighttime drop in body temperature: a physiological trigger for sleep onset?. Sleep, 20(7), 505-511
  2. Brinkman JE, Sharma S. Physiology, Sleep. StatPearls Publishing. Updated March 16, 2019.
  3. Singh S, Kaur H, Singh S, Khawaja I. Parasomnias: A Comprehensive Review. Cureus. 2018;10(12):e3807. doi:10.7759/cureus.3807
  4. Siegel JM. REM sleep: a biological and psychological paradox. Sleep Med Rev. 2011;15(3):139-42. doi:10.1016/j.smrv.2011.01.001
  5. Shapiro, C.M., R. Bortz, D. Mitchell, P. Bartel, and P. Jooste (1981). Slow-wave sleep: a recovery period after exercise. Science 214:125 3-125 4
  6. Caia, J., Kelly, V. G., & Halson, S. L. (2018). The role of sleep in maximising performance in elite athletes. Sport, recovery, and performance: Interdisciplinary insights, 151-167.
  7. Reimer, J., Feld, M., & Froböse, I. (2016). Schlaf & Sport–Feder und Nut der Fitness. Schlaf, 5(02), 64-66.