That's why getting enough sleep is just as important for your training regime as eating the right food or training in the gym.
How sleep deprivation affects your brain first
When you're sleep deprived the first noticeable effect will be on your brain. Researchers from the University of Tehran found that after one night's sleep deprivation the reaction times of college athletes (who were being measured in a cycling task) were adversely affected. But their anaerobic abilities (maximum power when exercising at full pelt) wasn't.
Other effects of sleep deprivation on the brain include:
Mood changes: One study found those who performed five hours of intermittent moderate exercise during 30 hours of sleep deprivation appeared more vulnerable to negative mood disturbances, as well as impaired reaction times, than another group who were just sleep deprived and didn't exercise. This put them at higher risk of accidents because they were less able to respond quickly.
Brain power: Another piece of research, published in Nature Neuroscience, found chronic jet lag could permanently affect brain power in air cabin crew who had the shortest intervals between flights over a five-year period. The researchers noted shrinkage in the temporal lobe region of the brain, which is critical for learning and memory.
Exercise feels harder: A study, published by European Journal of Applied Physiology and Occupational Physiology, found people who performed heavy exercise after 36 hours without sleep had a greater perceived level of exertion during a walk compared to those who slept, even though exercise heart rate and metabolic rate was unchanged. The researchers concluded the psychological effects of sleep loss may make those affected less tolerant of heavy exercise.
Physical effects of sleep deprivation on exercise
These can include:
Interference with tissue repair: A lack of sleep may increase levels of the stress hormone cortisol, and this may interfere with tissue repair and growth. Cognition may also be impaired, making it harder for you to concentrate whilst exercising.
Alters speed and technique: Getting less sleep can affect your athletic performance. A study, published by the American Academy of Sleep Medicine, found extending sleep to 10 hours per day enabled Stanford University swimmers to improve their 15-metre sprint times, reaction times and kick strokes.
Energy levels: Just one disrupted night of sleep can induce insulin resistance, which affects your body's ability to manage sugar and therefore energy levels. A study, found that healthy participants can become insulin-resistant after one night of getting only four hours sleep.
Post exercise recovery isn't as effective: Your body needs rest to restore itself. A study, published in Sports Medicine, found a reduction in sleep quality and quantity could affect your nervous system and may result in symptoms similar to overtraining syndrome, a condition where your body is pushed beyond its natural ability to recover, which can affect the immune system.
Several supplements can support your sleep and help ensure you are well-rested.
5-HTP is an amino acid, which helps the body produce the 'happiness hormone' serotonin. Serotonin is a pre-cursor to the sleep hormone melatonin.
Magnesium reduced mental and physical stress in one study, and the authors said it may help prevent sleep disorders.
Valerian can help promote relaxation and sleep. An overview of 18 studies found people taking valerian were 37 per cent more likely to say their sleep quality had improved compared to those taking a placebo. The researchers concluded valerian could be effective in terms of a subjective improvement in insomnia without the side effects associated with conventional sleeping pills.