Sleep: The ultimate ergogenic aid
Sleep is possibly the most important aspect of your 23-hour post-exercise recovery period, as this is when the real growth process occurs. The link between sleep, performance and muscle growth is a well known, scientifically-proven fact as your body enters an anabolic state during sleep where your muscles are repaired and recover from the exertion and damaged caused by exercise.
Adequate sleep also contributes to the restoration of the immune and nervous systems, and is responsible for maintaining normal levels of cognitive skills such as speech, memory, innovative, and flexible thinking. In other words, sleep is an essential part of life.
Sleep is defined as a state of suspended sensory and motor activity, characterised by total or partial unconsciousness and the inactivity of nearly all voluntary muscles and bodily functions. There are two main types of sleep, namely non-rapid eye movement (NREM) and rapid eye movement (REM) sleep.
The 4 Stages of Sleep
Sleep can be broken down into four stages or phases, with the first three occurring during NREM sleep and the fourth stage during REM sleep. Stage one is a relatively light sleep that lasts around 5-10 min at the start of a sleep cycle. Stage two lasts for approximately 20 min, where the brain begins to produce bursts of rapid, rhythmic brainwave activity known as sleep spindles. Your body temperature and heart rate also begin to decrease during this stage. Deep, slow brainwaves, known as delta waves begin to emerge during stage three sleep, which leads to a deep sleep that lasts for approximately 30 minutes. This is where you enter the fourth and final stage of sleep, known as REM sleep. This stage is characterised by an increased respiratory rate and brain activity. Sleep does not progress through these stages in sequence though and fluctuates through the various levels several times throughout the night.
The REM State
Muscles are most relaxed during the REM sleep state, which is when our bodies enter a heightened anabolic state and results in the rejuvenation and repair of the immune, nervous, skeletal and muscular systems. When you are in a state of deep sleep your body begins the process of specific adaptations to imposed demands (SAID), a training principle that basically means your body starts adapting to the stresses you imposed on it through the exertion, training and exercise you did earlier in the day.
A number of internal processes occur to make this happen, like a release of growth hormone (GH) and testosterone. Over 90% of your daily GH supply is actually released while you sleep, mostly during the first hour, and testosterone levels also become elevated. In fact, some research points to a direct relationship between the length of time you sleep and your circulating levels of testosterone.
Peripheral blood flow to your muscles also increases, as the blood supply demands of your internal organs are reduced. This is done to aid in the repair of damaged tissues. In the case of muscle tissue, increased blood flow shuttles the vital nutrients we assimilate through our diets to repair damaged and fatigued muscles. These nutrients include glycogen and the important building blocks of muscle tissue, amino acids which are derived from digested protein. Amino acids work to repair the micro-trauma caused by weight training or exercise, which enables our muscles to grow back bigger and stronger.
But what happens when you run out of protein and amino acids to fuel this recovery overnight?
After a few hours of sleep your body enters a state called nocturnal post-absorptive muscle catabolism or NPMC. This happens every night when the natural release of GH stops and you run out of digested protein to synthesise. In the past there was not much that could be done to stop or reduce this process, short of waking up and eating periodically throughout the night. Without these re-feeds catabolism would set in as your body would break down muscle tissue as a source of amino acids. However, these days slow release protein supplements are available that contain slow digesting proteins like casein. These products provide an adequate supply of slow assimilating, bioavailable protein throughout the night to ensure an anabolic state is maintained for longer periods during the sleep cycle.
“Losing even an hour of sleep a night will lead to sleep debt and ultimately results in a host of negative effects.”
The central nervous system (CNS) also uses sleep as a time to recover and recharge, allowing your body to function optimally at your next training session. As such, your body needs adequate sleep every night to function and grow optimally.