Sunday, 31 January 2016

The Importance of Sleep for Rowers


Its 6am most of the population are tucked up in bed, meanwhile the average rower has already started the warm up for their morning training session.  Success in rowing requires an almost unparalleled level of hard work, determination and self-discipline.  Early sessions on the water in freezing wet weather, intense land training coupled with the stresses of full time work or studies places an exceptional strain on the mind and body.  A key, and often underappreciated, aspect of maximising athletic performance is sleep. We could be excused for disregarding the importance of sleep, with stories from successful people like Nikola Tesla, Barrack Obama and Marissa Mayer getting by on just a few short hours.  Thomas Edison was notoriously quoted as saying “Sleep is a criminal waste of time and is a heritage from our cave days” and slightly more bluntly Maggie Thatcher simply said “Sleep is for wimps”.  However a disregard for sleep has the potential to derail even the most talented athlete.  As little as 3 hours of sleep restriction for one night has been shown to negatively impact exercise performance, reaction time, decision making, alertness and increase lactic acid and catecholamines (stress hormones) concentration.  Also perhaps in a cruel sense of irony increased training loads are associated with poor quality of sleep.  Elite athletes treat their sleeping habits like they do all other aspects of their training and lifestyle, they seek optimisation so peak performance can be achieved. 

Sleep Infographic credit to YLM Sport Science 


Usain Bolt 8-10 hours  
"Sleep is extremely important to me.  I need to rest and recover in order for the training I do to be absorbed by my body,"


Andy Murray up to 12 hours
"On the days when I am not playing I try to get in and do my work early, deal with ­everything else that has to happen, and then get home and have a nap.  I don’t normally have any ­trouble sleeping. I sleep well. You need rest to make sure you ­recover properly."

Roger Federer 11-12 hours
"If I don’t sleep 11-12 hours a day, it’s not right,"                                      

Larry Fitzgerald
"I always get my rest and I think that's one of the things that people don't talk often about. Your body heals and repairs itself better than anything. Being able to get some sleep really does a great cause for your recovery and helping you wake up with a renewed, fresh mental and physical outlook."

The Importance of Sleep
Sleep is defined as a homeostatically controlled behavioural state of reduced movement and sensory responsiveness.  The underlying mechanisms as to why sleep is so essential boil down to two main aspects. 
  • It has a restorative effect on both the immune and endocrine systems
  • It plays a role in cognition with links to memory, learning and the strengthening of the connections between neurons commonly referred to as synaptic plasticity.


When we sleep we got through multiple 90 minute sleep cycles, these cycles comprise of rapid eye movement sleep (REM) and non-REM sleep. Growth hormone and other anabolic hormones have been shown to be produced during N-REM.  Sleep restriction to 5 hours per night for one week reduced testosterone levels by 10-15% in young healthy males.  These hormones are of course essential for tissue regeneration and growth, but they also mobilise fatty acids to provide energy thereby preventing the loss of muscle.  This process is particularly important for rowers who are require rapid healing and repair, to deal with the intense training schedule.  On the other hand REM sleep is linked to brain activation and emotional regulation.  Both stages of the sleep cycle have been implicated in sleep dependant memory formation, and more specifically has been shown to effect ability in tasks related to physical movement.  Rowing requires a high level of mental discipline and concentration to maintain technique under extreme physical stress, therefore the cognitive benefits of getting enough sleep is just as important as the physical.  

Sleep Duration
So how much sleep do we need?  This is a complex question as there is a huge amount of inter-individual variability especially when it comes to athletes.  Generally a minimum of 8 hours is recommended, however athletes may require more.  Increasing sleep duration to 10 hours per night for 5-7 weeks in basketball players, increased their sprint time, shooting accuracy and reaction time.  A recent study in young men and women preparing for the world junior rowing championships, found that an increase in training negatively impacted sleep quality and duration.   This lead to reduced ratings of overall recovery and greater scores on a test of negative emotional state.  When training was reduced in the second half of camp sleep duration increased to 8 hours and scores of recovery and stress subsequently improved.
Infographic Summary for Study in Junior Rowers credit to YLM Sport Science 

Enhancing Sleep Quality
Getting good quality sleep is just as important as the total duration of sleep or time in bed.  This comes down to two main factors, sleep onset and preventing disturbances.

A substantial consideration for onset of sleep is light exposure, or rather exposure to particular wave lengths of light.  The circadian rhythm is a daily cycle of biological activity which includes sleep, controlled by the suprachiasmatic nucleus within the hypothalamus, and it is heavily influenced by exposure to light and dark.  The modern era has brought with it a number of technological advances including laptops, tablets and smart phones.  These devices emit a short wavelength enriched light, meaning they have a higher concentration of blue light than natural light.  Blue light has been shown to reduce levels melatonin, a hormone secreted by the pineal gland that is associated with the onset of sleep.  Over exposure to blue light from our devices can upset the sleep wake cycle and delay the onset of sleep.  This can be avoided by reducing exposure to these devices later in the day or by using blue light filters such as FLUX.  Making the bedroom as dark and quiet as possible can also help with the onset of sleep and reducing sleep disturbances.

Nutritionally there is some evidence to support strategies for preventing disturbance and enhancing onset of sleep.  The neurotransmitter 5-hydroxytryptophan is a metabolic intermediate in the biosynthesis of serotonin and melatonin.  Production of this neurotransmitter is dependent on the availability of the amino acid tryptophan.  Tryptophan needs to be transported over the blood brain barrier (a semipermeable membrane separating the blood from the cerebrospinal fluid), however the branch chain amino acids are preferentially transported ahead of tryptophan.  Branch chain amino acids play an important role in muscle growth and recovery, therefore athletes are recommended to consume foods rich in these amino acids (Meat, dairy and legumes).  Transport of tryptophan across the blood brain barrier can be enhanced by consuming a carbohydrate rich meal, stimulating insulin secretion which facilitates the transport of branch chain amino acids into muscle tissue resulting in increased free tryptophan.  A study conducted investigating this theory comparing high and low glycaemic index (GI) carbohydrate ingestion.  Consuming a high GI meal 4 hours before going to bed was found to be optimal compared to 1 hour before bed and low GI feedings at identical time points.  So judging by this evidence it would appear that consuming a meal containing high GI foods (e.g. white rice, potato and pasta) could enhance sleep quality, as long as it is consumed more than 1 hour before going to bed.  This is great news for rowers as if there is one thing rowers love its carbs.   

Summary


To conclude sleep is essential for performance and recovery in rowing.  It impacts both physiological and cognitive aspects and can be influenced by a number of environmental factors such as light exposure, training load and nutrition.  Optimising sleep environment, reducing blue light expose and imposing proper nutritional strategy could positively impact sleep onset, duration and quality and thereby positively influence training environment and competitive performance. 


References

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Fullagar, H., Skorski, S., Duffield, R., Hammes, D., Coutts, A. and Meyer, T. (2014). Sleep and Athletic Performance: The Effects of Sleep Loss on Exercise Performance, and Physiological and Cognitive Responses to Exercise. Sports Med, 45(2), pp.161-186.

Halson, S. (2014). Sleep in Elite Athletes and Nutritional Interventions to Enhance Sleep. Sports Med, 44(S1), pp.13-23.

Harrison, Y. and Horne, J. (2000). The impact of sleep deprivation on decision making: A review.Journal of Experimental Psychology: Applied, 6(3), pp.236-249.

K├Âlling, S., Steinacker, J., Endler, S., Ferrauti, A., Meyer, T. and Kellmann, M. (2016). The longer the better: Sleep–wake patterns during preparation of the World Rowing Junior Championships.Chronobiology International, pp.1-12.

Leproult, R. (2011). Effect of 1 Week of Sleep Restriction on Testosterone Levels in Young Healthy Men. JAMA, 305(21), p.2173.

Mah, C., Mah, K., Kezirian, E. and Dement, W. (2011). The Effects of Sleep Extension on the Athletic Performance of Collegiate Basketball Players. SLEEP, 34(07), pp.943-950.

Takahashi, Y., Kipnis, D. and Daughaday, W. (1968). Growth hormone secretion during sleep. Journal of Clinical Investigation, 47(9), pp.2079-2090.

Weitzman, E. (1976). Circadian Rhythms and Episodic Hormone Secretion in Man. Annual Review of Medicine, 27(1), pp.225-243.