By Jonathan Mike, Ph.D. (c) CSCS, NSCA-CPT, USAW
The two most common factors people think about when building muscle are training and nutrition. However, sleep quality and quantity are central to training and performance. And the fact is, most of us don’t get enough quality or quantity.
Sleep is critical to body homeostasis and circadian rhythm, which heavily influence the production of hormones and neurotransmitters. When we don’t sleep, our rhythm gets off-track, our hormones go crazy and we can’t recover as effectively. Loss of sleep impacts a wide variety of physiological outcomes — altered glucose control, abnormal cortisol and, of course, overall hormonal imbalances (such as lower testosterone in men), which impede training and recovery due to decreased protein synthesis and a cascade of other factors.
Most hard-training athletes need about seven to eight-and-a-half hours of sleep each day. A study published in the journal Neuropsychiatric Disease and Treatment showed that both short-term and chronic sleep deprivation led to significant decreases in cognitive function. Sleep also serves as a restorative process for energy resources, tissue recovery and thermoregulation, and deep sleep is vital for maximizing physiological growth and repair.
Testosterone levels are also profoundly affected by sleep. Research has shown that men who sleep between four and six hours have lower testosterone levels than men who sleep more than eight hours. This makes sense, as our bodies secrete more testosterone when we are asleep than when we’re awake. Since adequate sleep does boost testosterone, a lack of sleep can most certainly create a decrease in this muscle-building hormone. According to a study published in The Journal of the American Medical Association, getting three fewer hours of sleep for five days reduced testosterone by over 10%, whereas another report showed a 30.4% decrease. Interestingly, these reductions all happened within 24 hours of sleep deprivation. The good news is that getting enough sleep quickly reverses this loss.
A study published in The Journal of the American Medical Association found that men who suffered from flagging testosterone levels due to sleep deprivation could feel declines in mood and energy as their hormone level dropped throughout the day. Ten subjects (24 years old and healthy) were recruited and passed a series of difficult tests to screen for endocrine or psychiatric disorders and sleep issues. The participants spent three nights in the laboratory sleeping for up to 10 hours, and then eight consecutive nights sleeping less than five hours. Their blood was sampled every 15 to 30 minutes for 24 hours during the last day of the 10-hour sleep phase and the last day of the five-hour sleep phase.
The results showed that five hours of sleep decreased their testosterone levels 10 to 15 percent. It was also found that the men had the lowest testosterone levels in the afternoons on their sleep-restricted days, between 2 p.m. and 10 p.m. Each subject self-reported their mood and vigor levels throughout the study, and it was found that the young men reported a decline in their sense of well-being as their blood testosterone levels dropped. Their mood and vigor actually decreased more per day as the sleep-restriction part of the study continued.
The sleep-testosterone connection becomes that much more important as you age. In a study published in Sleep, testosterone was measured in 12 healthy, non-smoking men between the ages of 64 and 74. Their blood was drawn in the morning, and researchers recorded how many hours per night the men slept, which varied from 4.5 to 7.5 per 24 hours. It was found that the longer the men slept, the more testosterone there was circulating in their blood. Interestingly, the men who slept the least had a testosterone level of 200 to 300 ng/dL, which is fairly normal for this age range, but on the low end. However, the men who slept the most had a testosterone level twice as high (500 to 700 ng/dL), which is more than expected for men of that age.
Low testosterone has a host of negative effects for young men, and not just in sexual performance and reproduction. It’s also crucial in building strength and hypertrophy, as well as bone density. Based on all these results, it’s clear that sleep significantly affects testosterone — in a positive way with more sleep, and in a detrimental way when significant sleep loss occurs.
The bottom line for hard-training athletes is to view the quality and quantity of your sleep as important factors in your performance and physique goals.