“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.
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. Amongst teenage athletes studies show that a lack of sleep is associated with higher incidence of injury. 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. Sleep and exercise are both stimuli for growth hormone release from the anterior pituitary, which mediates some of these adaptive effects.
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. 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.
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. In a fascinating recorded lecture delivered by Professor Jim Horne at the Royal Society of Medicine, 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 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 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. Recent research demonstrates that protein intake before bed can support skeletal and muscle adaptation from exercise and also recovery from tendon injury  . Conversely there is recent report that low levels of serotonin synthesis may contribute to the pathogenesis of autoimmune inflammatory disease 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.
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.
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
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