“Sleep.. chief nourisher in life’s feast,” Macbeth.

By Dr Nicky Keay

A recovery strategy vital to support both health and sport performance, during all stages of the training cycle is sleep. In this blog I outline the importance of sleep for athletes of all ages and calibres.

Young athletes

Sufficient sleep is especially important in young athletes for growth and development and in order to support adaptive changes stimulated by training and to prevent injury[1]. Amongst teenage athletes studies show that a lack of sleep is associated with higher incidence of injury[2]. This may be partly due to impaired proprioception associated with reduced sleep. Sleep is vital for consolidating neurological function and protein synthesis, for example in skeletal muscle and in the longer term bone mineral density[3]. Sleep and exercise are both stimuli for growth hormone release from the anterior pituitary, which mediates some of these adaptive effects[4].

Sufficient sleep quality and quantity

Sufficient sleep is especially important for athletes in heavy training. Lack of sleep can interfere with functioning of the immune system due to disruption of the circadian rhythm of secretion in key areas of the Endocrine system[5]. Athletes in heavy training, with high “stress” loads and associated elevated cortisol can also experience functional immunosuppression. So a combination of high training load and insufficient sleep can compound to disrupt efficient functioning of the immune system and render athletes more susceptible to illness and so inability to train, adapt and recover effectively. In overreaching training, lack of sleep could be either a cause or a symptom of insufficient recovery. Certainly sleep deprivation impairs exercise performance capacity (especially aerobic exercise) although whether this is due to a psychological, physical or combination effect is not certain[6].

Sufficient sleep quality and quantity is required for cognitive function, motor learning, and memory consolidation. All skills that are important for sport performance, especially in young people where there is greater degree of neuroplasticity with potential to develop neuromuscular skills [7] . In a fascinating recorded lecture delivered by Professor Jim Horne at the Royal Society of Medicine[8], the effects of prolonged wakefulness were described. Apart from slowing reaction time, the executive function of the prefrontal cortex involved in critical decision making is impaired. Important consequences not only for athletes, but for doctors, especially for those of us familiar with the on call system in hospitals back in the bad old days. Sleep pattern pre and post concussive events in teenage athletes [9] is found to be related to degree and duration of concussive symptoms post injury. The explanation of how sleep deprivation can cause these functional effects on the brain has been suggested in a study where subtle changes in cerebral structural neuronal structure[10] were recorded. It is not known whether these changes have long term effects.

Strategies to maximize positive benefits of sleep

So given that sleep is essential not only for health and fitness, but to support sports performance, what strategies maximise this vital recovery process? Use of electronic devices shortly before bedtime suppresses secretion of melatonin (neurotransmitter and hormone), which is not conducive for sleep. Tryptophan is an amino acid precursor in the synthesis of melatonin and serotonin (neurotransmitter) both of which promote sleep[11]. Recent research demonstrates that protein intake before bed can support skeletal and muscle adaptation from exercise and also recovery from tendon injury [12] . Conversely there is recent report that low levels of serotonin synthesis may contribute to the pathogenesis of autoimmune inflammatory disease[13] such as rheumatoid arthritis. This highlights the subtle balance between degree of change required for positive adaptation and a negative over-response, as in inflammatory conditions. This balance is different for each individual, depending on the clinical setting. So maybe time to revisit the warm milky drink before bed? Like any recovery strategy, sleep can also be periodised to support exercise training, with well structured napping during the day as described by Dr Hannah Macleod, member of gold winning Olympic Hockey team[14].

In conclusion, when you are planning your training cycle, don’t forget that periodised recovery to compliment your schedule should be factored in, with sleep a priority recovery and adaptation strategy.

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If you want to read more about short and long term strategies to improve sport performance read my blog (on my personal page): Balance of recovery and adaptation for sports performance

Dr Nicky Keay BA, MA (Cantab), MB, BChir, MRCP, Clinical and research experience in Endocrinology applied to Sport and Exercise Medicine

[1] Milewski MD, Skaggs DL, Bishop GA, Pace JL, Ibrahim DA, Wren TA, et al. Chronic lack of sleep is associated with increased sports injuries in adolescent athletes. Journal of pediatric orthopedics. 2014 Mar;34(2):129-33

[2] Luke A, Lazaro RM, Bergeron MF, Keyser L, Benjamin H, Brenner J, et al. Sports-related injuries in youth athletes: is overscheduling a risk factor? Clinical journal of sport medicine : official journal of the Canadian Academy of Sport Medicine. 2011 Jul;21(4):307-14

[3] Keay N, Dancing through adolescence. Editorial, British Journal of Sports Medicine, vol 32 no 3 196-7, September 1998.

[4] Keay N, Logobardi S, Ehrnborg C, Cittadini A, Rosen T, Healy ML, Dall R, Bassett E, Pentecost C, Powrie J, Boroujerdi M, Jorgensen JOL, Sacca L. Growth hormone (GH) effects on bone and collagen turnover in healthy adults and its potential as a marker of GH abuse in sport: a double blind, placebo controlled study. Journal of Endocrinology and Metabolism. 85 (4) 1505-1512. 2000

[5] Lange T, Dimitrov S, Born J. Effects of sleep and circadian rhythm on the human immune system. Annals of the New York Academy of Sciences. 2010 Apr;1193:48-59.

[6] Hausswirth C, Louis J, Aubry A, Bonnet G, Duffield R, Le Meur Y. Evidence of Disturbed Sleep and Increased Illness in Overreached Endurance Athletes. Medicine and science in sports and exercise. 2013 Oct 1.

[7] Myer GD, Faigenbaum AD, Ford KR, Best TM, Bergeron MF, Hewett TE When to initiate integrative meuromuscular training to reduce sports-related injuries and enhance health in youth? Curr Sports Med Rep 2011 May-June:10(3):155-66

[8] “Sleepiness and critical decision making”. Recorded lecture Professor Jim Horne, Royal Society of Medicine 16/11/16

[9] Sufrinko A, Pearce K, Elbin RJ, Covassin T, Johnson E, Collins M, et al. The effect of preinjury sleep difficulties on neurocognitive impairment and symptoms after sport-related concussion. The American journal of sports medicine. 2015 Apr;43(4):830-8.

[10] Bellesi M, Pfister-Genskow M, Maret S, Keles S, Tononi G, Cirelli C.

Effects of sleep and wake on oligodendrocytes and their precursors.

J Neurosci. 2013 33: 14288–14300. DOI: 10.1523/JNEUROSCI.5102-12.2013

[11] Hartmann E. Effects of L-tryptophan on sleepiness and on sleep. Journal of psychiatric research. 1982;17(2):107-13.

[12] Jorn Trommelen, Luc J. C. van Loon Pre-Sleep Protein Ingestion to Improve the Skeletal Muscle Adaptive Response to Exercise Nutrients 2016, 8(12), 763

[13] Yasmine Chabbi-Achengli, Tereza Coman, Corinne Collet, Jacques Callebert, Michelangelo Corcelli, Hilène Lin, Rachel Rignault, Michel Dy, Marie-Christine de Vernejoul, Francine Côté

Serotonin Is Involved in Autoimmune Arthritis through Th17 Immunity and Bone Resorption

The American Journal of Pathology, 2016; DOI: 10.1016/j.ajpath.2015.11.018

[14] “Science in Elite Sport” Dr Hannah Macleod, University of Roehampton, 6/12/16

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