Sleep; it takes up approximately a third of our lives, has important biological functions and processes such as endocrine function, learning, memory and cognition. It alters how the body works , and can be an athlete’s best friend, or worst enemy.
It’s generally accepted that sleep helps to promote recovery from the tasks undertaken when previously awake and helps to prepare the body for the following day. Therefore it can be said that sleep has a marked impact on an individual’s day time functioning as sleep restriction, or deprivation over consecutive nights can lead to a decline in cognitive function, mood, appetite, glucose metabolism and immune function. Sleep in non athletic populations is well documented, with guidelines suggesting that ~8 hours of sleep per night is adequate to overcome any neurobehavioral deficits caused by sleep deprivation. However, there is less evidence and guidelines for the athletic population. Since sleep has been reported to promote recovery, it can be speculated that athletes who partake in high volumes of training may require longer sleep cycles. Therefore, the question remains; is longer better?
Interestingly, under periods of high stress and training volume load, more sleep appears to decrease subjective markers of stress in 55 junior national rowers during a four week training camp. As athletes have intensive training schedules, i.e. multiple training sessions per day with the first sessions starting ~6.30-7am and final sessions finishing ~8pm; sleep restriction is a common theme. It has been reported that sleep issues arise the night before competition, of which over two thirds of German athletes reported sleep problems such as the inability to fall asleep, waking up early and frequently awakening during sleep. Anecdotally, it has also been reported that athletes who compete in the evening struggle with falling asleep – potentially due to the psychological strain of competition such as, self analysis and criticism alongside caffeine use.
Research into methods of aiding sleep is saturated; from pharmaceuticals, to meditation, routines on sleep hygiene and even taking your own bedding to different hotels when travelling (as does Team GB Cycling). However, this article aims to tackle sleep issues from a nutritional stand point in order to improve; the time taken to fall asleep, sleep quality and sleep duration.
Here’s what you need to know.
- Chronic sleep deprivation of 24-64 hours has mixed findings on performance parameters. Twenty-four hours of sleep deprivation appears to not influence anaerobic power, however impaired performance is seen after being awake for 36 hours. Suggesting that there may be a dose response. Furthermore, it is suggested that sleep deprivation is task specific. This has been demonstrated with 64 hours of sleep deprivation where it was found that vertical jump and knee extension strength was significantly affected – However isometric strength and 40m sprint performances were not. Interestingly, performance in strength sports such as weightlifting that requires a high level of skill and concentration was not affected with 24 hours of sleep deprivation. However mood states, fatigue, vigour and level of confusion were observed.
- As chronic sleep deprivation is rare amongst athlete, most athletes will experience periods of partial sleep deprivation of only a few hours per night – Interestingly, this appears to not affect maximal effort performances. The negative effects of short term sleep restriction on consecutive nights are fund to influence submaximal exercise, and mood disturbances such as; depression, tension, confusion, fatigue, anger, and decreases in vigour- More so during the latter days suggesting a cumulative effect.
- If inadequate sleep is experienced – Try taking a 30 minute nap. The reduced 20m sprinting performances displayed after only four hours of sleep deprivation was improved by having a 30 minute nap at lunchtime. Other improvements seen were in the level of sleepiness and alertness, and in other instances shown to improve cognitive performances which are paramount in strategy and tactical phases of competition. As there appears to be little, if any negative issues with napping, if you’re tired – sleep it off.
- If you can, sleep longer. Increased sleep time to ~10 hours per night improved sprint times, free throw accuracy, reaction time, mood, vigour and reduced fatigue in basketball players and swimmers.
Several neurotransmitters have been identified to regulate sleep; Serotonin, gamma-aminobutyric acid (GABA), orexin, melanin-concentrating hormone, cholinergic, galanin, noradrenaline, and histamine.
Nutrition guidelines to improve sleep are aimed to interact with these neurotransmitters.
- Melatonin is a hormone that controls your sleep and wake cycles primarily through light and dark exposure, i.e. day and night. The amino acid; Tryptophan plays a fundamental role in increasing melatonin’s pre-cursor Serotonin when crossed the blood brain barrier. Increasing Tryptophan uptake into the brain can be done in several ways….although, carbohydrate intake appears to be key.
- Consuming a high carbohydrate meal (130g) compared to a lower carbohydrate meal (47g) and a zero carbohydrate meal 45 minutes prior to sleeping improved REM sleep, decreased light sleep, and wakefulness. However, it should be noted that consuming this quantity of carbohydrates prior to sleep if in a calorie/carbohydrate restricted diet may decrease performance due to reduced carbohydrate availability to sustain exercise performance. I.e. balance and distribute carbohydrate intake wisely to get the best of both worlds; sleep quality and performance.
- Favouring higher glycemic index (GI) carbohydrates appears to be superior than lower GI carbohydrates when consumed 4 hours prior to sleep. Furthermore, consuming the meal 4 hours prior compared to 1 hour prior improved how quickly sleep occurred (sleep onset latency).
- Diets high in carbohydrate may result in a shorter time to fall asleep, diets high in protein may result in improved sleep quality, and diets high in fat may negatively influence total sleep time . In other words, what is generally recommends for athletes with a high(er) training load and frequency.
Emptying the kitchen sink:
- Tryptophan in a low dose of 1g appears to improve sleep quality and decrease the time taken to fall asleep. This can be achieved without supplementation by eating ~300g of turkey prior to sleep. This will also complement improved rates of recovery from exercise as higher doses of protein consumed prior to bed appears to be superior than lower doses, or nothing at all.
- Melatonin appears to be safe for short-term use, however there was no evidence that melatonin was effective for most primary sleep disorders although may decrease the time taken to fall asleep if experiencing insomnia. Seek medical advice prior to usage as melatonin in supplement or pharmacological form may have side effects such as headaches, nausea, daytime sleepiness, and vivid dreams and nightmares.
- Tart Cherry Juice may also increase melatonin concentrations, and when supplemented for two weeks improvements in sleep time and subjective sleep quality were noticed.
- Valerian is a herb that reduces the activity of the nervous system by binding to GABA receptors. It is thought to have calming effects and subjectively improves sleep quality. However individuals may experience side effects such as; drowsiness, dizziness and allergic reactions.
Many popular sleeping aids remain on the market with little evidence to suggest how well they work – such as; passionflower, kava, St. John’s wort, lysine, magnesium, lavender, skullcap, lemon balm, magnolia bark, 5-hydroxytryptamine, and GABA. Furthermore, if an athlete wishes to experiment with these supplements, it is advisable that they seek HFL tested products for contaminated substances – Always look out for the Informed Sport logo on products.
There you have it, your ‘go to’ nutrition hacks that can be used to troubleshoot your sleep.