It’s a quite common sight to see a person go for his bag after exercise and have his post-workout shake packed with protein. By a recent review article (Morton et al. 2018) protein supplementation combined with strength training boosts your muscle growth which is pretty well-known fact among fitness community. You don’t hear too often someone being worried about their sleep but rather their nutrition. If an athlete, keen on maximizing her strength results, forgets her shaker at home she might be seen acting troubled and heard ranting something about “losing her gains”. Should she be equally concerned if she loses her sleep?

Sleep restriction has only negative effects on your performance

Sleep restriction (SR) means that the duration of your sleep is purposely made shorter. It can be done either by delaying the bedtime or waking up earlier than normal.
Fullagar et al. (2015) investigated effects of sleep loss on their review article and found out that SR might decrease sport specific skill performance (e.g. accuracy of tennis serves), submaximal strength (e.g. weight on sets), muscular power (e.g. standing long jump) and anaerobic power (e.g. 400m sprint). In contrast, SR doesn’t appear to decrease aerobic or maximal strength performance, although mixing results exists.

Even minor SR has been shown to increase reaction times which is quite critical for athletes relying on this component (e.g. goalkeepers and sprinters). SR has also negative effect on mood states, like decreased vigor and increased depression and sleepiness. These negative effects have been linked to a harmful state of over-training. You can also imagine that feeling sleepy and depressed, it can be hard to motivate you to push through a hard exercise or even get up from the couch!

Staying up late disturbs hormonal function

Growth hormone (GH) is a hormone which is produced in human body throughout life, with highest values during puberty. Most of the GH is produced during night but exercise causes the release of GH as well. It has a major role regulating growth of human being but it also helps to maintain normal metabolism. GH plays also a part on the repair process of muscle after a workout. Therefore, combined with strength training, GH helps your muscles grow. (Godfrey et al. 2003.)

50 years ago, Takahashi et al. (1968) demonstrated the release of GH into blood flow during sleep and that the highest peak in the GH levels occurred in the early hours of sleep. If bedtime was delayed, the GH peak during night was lower and it lasted a shorter period of time.

Growth hormone levels in blood during normal and delayed sleep (Takahashi et al. 1968).

If you stay up late you might miss that GH peak! You don’t want that to happen if you want to maximize your strength and muscle mass gains.

Sleeping habits of elite athletes

National Sleep Foundation (2015) recommends 7 – 9 hours of sleep for 18 – 64 years old adults and often athletes are recommended to sleep even more. Fullagar et al. (2015) summarizes findings on sleep behavior among athletes on their review article. A survey of 890 elite South African athletes demonstrated that about 75 % of them slept between 6 and 8 hours. Comparison of Olympic athletes and non-athletic controls showed that athletes had slightly shorter objectively measured sleep time than controls (6 h 55 min vs. 7 h 11 min) and they also had poorer sleep quality. Early morning training was shown to dramatically restrict world-class swimmers sleep duration compared to their normal sleep (5.4 h to 7 – 8 h). Additionally, high intensity exercise late in the evening delayed bedtime by 14 minutes and increased heart rate at bedtime by 25.7 bpm compared to controls.
By this information it appears that even all elite athletes aren’t getting enough sleep! Also, athletic lifestyle itself with stressful competitions and early morning or late evening exercises might disturb their sleeping. Could these athletes improve their performance by sleeping longer?

Sleeping more

Mah et al. (2011) extended sleep time of varsity level basketball players from 6.6 hours to 8.4 hours for 5 – 7 weeks. Sleep extension improved athletes sprint and reaction times and shooting accuracy of various throws. Subjective sleepiness also decreased and overall mood increased. Sleep was objectively measured with a device attached to wrist.

Athletic performance before sleep extension and after it

Athletic performance before sleep extension and after it (Mah et al. 2011).

Similar study was conducted by Schwartz & Simon (2015) with varsity tennis players. Sleep time was extended from 7.14 hours to 8.85 hours for one week. Accuracy of tennis serves improved significantly after the sleep extension (35.7 % to 41.8 %) and subjective sleepiness also declined. On this study sleep was reported subjectively by athletes themselves.
Extending sleep to match the recommendations clearly increased performance of these athletes and also reduced the subjective feeling of sleepiness!

To answer the question raised in the beginning of the article, yes, she should be concerned about losing her sleep. Duration of sleep does affect your athletic performance. Restricted sleep appears to decrease sport specific skill performance, submaximal strength and muscular and anaerobic power. Also, reaction time is decreased easily and negative effect of sleep restriction on your mood might influence your training motivation. You should aim close to 9 hours of sleep per night to avoid any negative effects on your athletic performance. Keep in mind though that time in bed doesn’t fully represent the actual duration of sleep! Some time passes by before you fall asleep and you might wake up few times during the night.

References:

Fullagar, H. H. K., Skorski, S., Duffield, R., Hammes, D., Coutts, A. J. & Meyer, T. 2015. Sleep and Athletic Performance: The Effects of Sleep Loss on Exercise Performance, and Physiological and Cognitive Response to Exercise.

Godfrey, R. J., Madgwick, Z. & Whyte, G. P. 2003. The Exercise-Induced Growth Hormone Responses in Athletes. Sports Medicine 33 (8), 599 – 613.

Mah, C. D., Mah, K. E., Kezirian, E. J. & Dement, W. C. 2011. The Effects of Sleep Extension on the Athletic Performance of Collegiate Basketball Players. Sleep 34 (7), 943 – 950.

Morton, R. W., Murphy, K. T., McKellar, S. R., Schoenfeld, B. J., Henselmans, M., Helms, E., Aragon, A. A., Devries, M. C., Banfield, L., Krieger, J. W. & Phillips, S. M. 2018. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. British Journal of Sports Medicine.

National Sleep Foundation. https://sleepfoundation.org/press-release/national-sleep-foundation-recommends-new-sleep-times. Refered 25th of February 2018.

Schwartz, J. & Simon, R. D. 2015. Sleep extension improves serving accuracy: A study with college varsity tennis players. Physiology & Behaviour 151, 541 – 544.

Takahashi, Y., Kipnis, D. M. & Daughaday, W. H. 1968. Growth Hormone Secretion during Sleep. The Journal of Clinical Investigation 47, 2079 – 2090.