By Casey Jones (@CaseyMAJones)
Are You Getting Enough Sleep?
If you’re among the 60% of Canadians that report fewer than eight hours of sleep, you likely need to get to bed sooner.
Under a threshold of seven hours of sleep, we can suffer from worsened mood, confusion, depression, and overall impaired cognitive function. At a chronic level of sleep loss, risk of health problems like cardiovascular disease and obesity greatly increases. Sufficient sleep is needed to keep our nervous, immune, and many other systems of your body healthy. For athletes, lack of sufficient sleep can be the reason for decreased performance and increased injury risk.
Sleep Biology 101
Our sleep-wake cycle is regulated by what is called the circadian rhythm, a biological clock that resets approximately every twenty-four hours. This cycle is synchronized to the daily light-dark cycle and the appearance of natural light. When the sun rises, light hits specialized cells in the retina of your eye that have a direct neuronal connection to your brain.
Your brain sends messages to the rest of your body to increase blood pressure, stimulate testosterone secretion, and alertness when your eyes detect light. As a result, we are generally at our most alert in the late morning after a good night’s sleep. The circadian rhythm takes a small dip in the afternoon for most, resulting in a drowsy feeling that tends to populate coffee-shop lines around 3:00 PM.
The master clock managing our circadian rhythm is called the suprachiasmatic nucleus (SCN). This area sends signals to other parts of the brain to regulate how awake we feel based on the light entering our eyes. Once the sun sets, the lack of light penetrating the eyes signals to the brain to release melatonin, a hormone associated with sleep onset. If our body regulates our sleep cycle in such an elegant manner, why don’t we always sleep enough?
Sleep deficits are caused by a multitude of reasons: commitments to our family, friends, careers, and studies commonly cause us to sleep less than our bodies desire. Social jet lag refers to the clash between the amount of sleep that our body needs and the activities that our lives demand that interfere with sleep. The researchers who coined the term found that there is approximately a one-hour disconnect of sleep times on weekdays versus weekends, which leads to a further dysregulation of the circadian rhythm in those who have trouble sleeping (Roenneberg et al., 2013).
Sleep and Performance
Research has shown that a lack of sleep hinders performance not only in daily life, but also plays an enormous role in athletic performance. Some of the world's best athletes get over ten hours of sleep a night, like NFL MVP JJ Watt and three-time Super Bowl winner Tom Brady.
When athletes suffer from sleep restrictions due to reasons like travel schedules, stressful competitions, and inappropriate caffeine intake, performance often suffers. A recent look at 47 Olympic athletes showed that they slept less on average compared to non-athletic individuals (Leeder et al., 2012). In general, a lack of sleep contributes to decreased cognitive and physical performance - depending on the sport you participate in.
A 2007 study of olympic-weightlifters that were deprived of sleep for 24 hours showed that although fatigue, confusion, and motivation deteriorated after sleep loss, maximal performance in the snatch, clean and jerk, and front squat was unaffected (Blumert et al., 2007). However, when a group of weightlifters were restricted to only three hours of sleep for three successive nights, their performance in bench press, leg press, and deadlift suffered (Reilly & Piercy, 1994). Other studies that have imposed increased levels of sleep on athletes show that sleeping 10 hours per night increased sprint and reaction time in a group of swimmers (Mah, 2008). Studies in athletes often involve extreme levels of sleep restriction or total sleep deprivation, which may not be reflective of the real sleep problems that athletes face.
Many studies with respect to athletic performance and sleep have been conflicting; however, what is consistent is that cognitive performance declines with sleep. Reaction time, alertness, memory and decision making have been reported to decline with less than 7 hours of sleep per night (Fullagar et al., 2015). For example, reaction time is slower with only one hour of sleep restriction over two nights (Bonnet, 1986).
Slowed reaction time can lead to reduced performance for sprinters coming out of the blocks, goalkeepers reacting to a shot, and defensive linemen reacting to the snap of a football. Even losses to short-term memory caused by sleep loss can affect recall of predetermined plays in sports like hockey, basketball, and soccer. Many athletic disciplines involve critical decision making and concentration, therefore sleep losses should be minimized as much as possible for athletes.
Sleep & Genetics: Not Everyone is the Same
While the general guideline recommends 7-9 hours of sleep per night, this does not apply to everyone. Ever wonder why your co-worker or teammate needs only six hours of sleep to function at the same level you do with eight or more? The answer may lie within your DNA.
Dozens of genes have been associated with difficulty falling asleep, amount of sleep required, and even being a “morning person.” Your circadian rhythm is tightly controlled by your genes, like the CLOCK gene that plays an important role in regulating the signals critical for a normal circadian rhythm. Variation in the gene is associated with shorter sleep duration, increased insomnia, and impaired dietary intake. Other genes like PDE4D play a role in communicating when it is time to sleep, and variation may result in some individuals having increased daytime drowsiness.
Since your genes may play a role in how much sleep you need, find an amount that’s right for you within the 7-9 hour recommendation and follow our tips for getting a good night’s sleep. Your performance on the track, gym, court, and in the office depends on it.
Casey Jones is a Research & Marketing Assistant at Athletigen. He is completing his honours degree in Microbiology & Immunology from Dalhousie University in Fall 2016, and is one of the captains on the Dalhousie Tigers Football team.
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