We have all suffered a sleepless night and have experienced the impact this has in the short term on our mood and productivity. Whilst some people have the occasional episode (normally due to disruption in routine- travel, socialising, children) , some can have more regular periods of poor sleep. We all hear about optimal sleep time and the importance of sleep on daily function, but what is the real impact of poor sleep on the body?
While asleep your body alternates between two forms of sleep: rapid eye movement (REM) and non-REM sleep. This cycle repeats several times throughout the night. REM sleep is associated with learning new information and maintaining important neural pathways. It is proposed that this stage of sleep is important for our memory -the kind that helps us to know how to do things, as well as “creative problem solving and motor skills.” It is during this period that we dream and the stage that results in us feeling refreshed when we wake from sleep. Unfortunately if we do not get an adequate amount of sleep it is the REM sleep that is sacrificed.
Non-REM sleep, known as slow-wave or deep sleep, is essential for restoring the body. It is broken up into 3 stage N1, N2 and N3.
When a person gets drowsy, we are drifting into N1 sleep. This is a relatively light form of sleep that lasts about 5 to 10 minutes. During this stage, heart and breathing rates begin to slow, eye movements also slow, and muscles relax. Body temperature decreases, and brain waves. You can easily wake someone from N1 sleep. N1 sleep is the first stage entered when taking a nap. The 2nd second stage of non-REM sleep typically lasts 10 to 25 minutes. During this stage, eye movement stops, heart rate slows, brain waves become slower and muscles relax even further. A person spends more time in stage N2 sleep than in any other sleep stage. Non-REM sleep then progresses into the ”slow wave,” “delta” or “deep” sleep. This is a period of deep sleep that is needed for an individual to feel refreshed for the next day. This typically lasts 20 to 40 minutes, N3 sleep is when the brain becomes less responsive to external stimuli, and as a result, it is most difficult to wake a person up from this stage. When you wake someone from this stage they will often be groggy and disorientated. This is why napping for more than 20-30mins is discouraged as any longer and there is a risk that you will enter N3 stage and not feel refreshed. Slow-wave sleep occurs for longer periods in babies and young children, and the time spent in N3 sleep decreases gradually as we age. We typically spend about 15 percent of their total sleep time in stage N3.
So what is the effect of a lack of sleep?
The odd sleepless night in reality is unlikely have to have any long term effects, however consistent sleep deprivation can have bigger repercussions on injury risk, illness risk and mental health.
As your body enters into the non-REM deep sleep stage, your pituitary gland releases growth hormone that stimulates tissue growth and muscle repair. Lack of sleep and changes in sleep quality cause a sharp decline in growth hormone secretion. Growth hormone deficiency is associated with increased obesity, loss of muscle mass and reduced exercise capacity. Sleep is not only an important aspect of recovery from day to day tasks but also imperative for recovery from intense training. A reduction in sleep volume and/or quality does increase you risk of injury. A study by Van Rosen et al. (2016) demonstrated that athletes that slept for less than 8 hours had a 1.7 times greater risk of injury and Prather et al (2015) found those that slept for less than 5 hours a night were 4.5 times more likely to suffer with the common cold than those that slept for 7 hours.
So what can you do to improve your sleep quality? Improving your sleep routine or sleep hygiene can have excellent effects on your quality of sleep. Below are a list of key tips for getting that good night’s sleep.
- dark and quiet rooms
- cool room temperature
- reduce physical and mental activity within the few hours before sleep
- restrict use of blue light devices (iPhones, iPads, computers) which suppresses melatonin production
- use dim lights 2 hours before bedtime
- maintain a consistent routine-even on weekends
- avoiding caffeine and alcohol in the afternoon/evening
So we can see there is a strong relationship between sleep and muscle recovery and this highlights how important high quality sleep is in maximising training effects and preventing illness/injury. Ensuring you get a good night’s sleep could help you to recover faster, or prevent you from the injury in the first place!