The Eric Cressey Blog welcomes a guest entry by Maki Riddington:

Even though we spend a third of our lives sleeping, scientists are still trying to learn exactly why people need sleep. In animal studies it has been shown that sleep is necessary for survival. For example, while rats normally live for two to three years, those deprived of REM sleep survive only about 5 weeks on average, and rats deprived of all sleep stages live only about 3 weeks. In humans, those who had been deprived of just one night’s sleep were shown to have a reduction in mental exertion. In real life situations, the consequences of being sleep-deprived are grave. Some speculation has linked sleep-deprivation to certain international disasters such as the Exxon Valdez oil-spill, Chernobyl, Three Mile Island and the Challenger shuttle explosion.

Taking this into the gym can mean that the ability to concentrate and focus can become compromised which means less of an effort and intensity in the workout (9). Hopefully it’s not leg day.

Athletes who suffer from sleep-deprivation have been shown to see a decrease in cardiovascular performance (10), that is, their time to exhaustion is quicker. Sleep-deprivation in studies has been shown to occur around 30-72 hours. For an athlete who has a full course-load, studies, mid terms, and trains, sleep-deprivation can accumulate very rapidly.

Another study looked at cortisol and performance levels after staying up for an 8-hour period overnight. Performance declined and cortisol levels increased. For someone looking to pack on muscle and increase strength, this is bad news since the main focus is to minimize cortisol release since it is a catabolic hormone (11).

From a fat loss perspective, sleep deprivation can impair fat loss through a decrease in levels of the satiety hormone leptin, and increases in the hunger hormone ghrelin. According to Dr. Van Cauter a professor of medicine at the university of Chicago, “One of the first consequences of sleeplessness is appetite dysregulation.” “Essentially, the accelerator for hunger [ghrelin] is pushed and the brake for satiety [leptin] is released.” “The leptin levels are screaming ‘More food! More food!’” What this means is that the hormone leptin is responsible for telling the body when it is full. However, with decreased production of this hormone, the body will crave calories (especially in the form of carbs) even though its requirements have been met. For someone trying to diet, good luck!

Voluntarily sleeping less than 6 hours per night has been associated with an increased incidence of impaired glucose tolerance, according to a cohort analysis of the Sleep Heart Health Study (SHHS) reported in the Archives of Internal Medicine. (12) This may mean that a chronic lack of sleep can impair glucose tolerance, which can make body recomposition a difficult task. Most people have a hard enough time trying to regulate their carbohydrates and time them so that the body metabolizes them efficiently.

So, if you’re getting the required 8 hours of sleep, are you ok? Well, if this sleep is broken up, then its value decreases as the sleep cycle is interrupted. Deep sleep appears to be connected with the release of growth hormones in young adults. Many of the body’s cells also show increased production and reduced breakdown of proteins during deep sleep. Since proteins are the building blocks needed for cell growth and for repairing bodily stress (muscle damage from strength training), uninterrupted deep sleep plays an important role in recovery and regeneration of the body.

Finally, adequate sleep and a properly functioning immune system are closely related. Sleep-deprivation compromises the immune system by altering the blood levels of specialized immune cells and important proteins called cytokines. These chemical messengers instruct other immune cells to go into action. As a result of being compromised, greater than normal chances of infections are likely to occur. And we all know that being sick can be a big setback both in and out of the gym.

Maki Riddington