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Sleep deprivation: how does it affect performance?
As a conditioning coach, I am often faced with young athletes who are struggling to balance the pressures of work or study with a sports career. It is not unusual for them to feel that there are just not enough hours in the day to fit everything in. Unfortunately, the first thing to suffer is usually their sleep. Late night revision sessions coupled with early morning practices can result in athletes trying to survive on as little as 4-6 hours sleep per night. If this pattern is extended for a number of weeks, you will very soon be dealing with an athlete who is burnt out, lacking motivation and struggling to find form in his/her chosen event. In order to be able to help an athlete who may have poor sleeping patterns it is important to understand what happens during sleep, how this can affect athletic performance and provide some simple guidelines to help such athletes achieve a good night’s sleep. Fortunately, experts from Wheaton College in the US have provided some basic information that will help coaches and trainers gain a better understanding of what happens during sleep and how it can affect performance.
The US study found that athletes have an increased need for total sleep time, and slow-wave sleep was found to be the most beneficial type. According to Peter Walters, Assistant Professor of Kinesiology at Wheaton College, sleep can be broken down into five stages.
Just before you fall asleep, beta brain waves (the type of brain waves that occurs when you are awake) are replaced by alpha waves. Alpha waves indicate a state of being awake yet deeply relaxed. Once you have been in this state for between 5-20 minutes, the mind and body will be ready for the first stage of sleep.
Stage one: This stage can last between 10 seconds and 10 minutes and is a light sleep. Breathing becomes shallow and your muscles rapidly begin to relax (sometimes giving you a sense of falling, which can result in a physical reflex such as kicking out with your legs).
Stage two: This stage lasts between 10 and 20 minutes and experts believe that it marks the beginning of actual sleep, as most people are virtually blind and deaf to most external stimuli.
Stage three and stage four: You now start to enter the deepest part of your sleep and this is a close as humans get to becoming a hibernating bear or hedgehog! Experts have found that the body’s recoveryprocesses peak during these stages, metabolic activity is at its lowest and the hormonal system increases the release of growth hormone. After about 30-40 minutes at stage four you will retrace stages three and two, but instead of returning to stage one you will move into rapid eye movement (REM) sleep.
REM: A lot happens during REM sleep. Blood flow, pulse, breathing, temperature and blood pressure all rise and your eyes move rapidly as if scanning the environment (fortunately your eyelids remain closed, as it would look a little strange if your eyes were wide open). During this stage dreams often occur, beta brain waves reappear (reflecting an active brain) but the body remains motionless due to the motor cortex blocking neurological activity at the brain stem. This is a very useful mechanism as it prevents us from acting out our dreams.
The cycle of sleep stages is repeated between four and six times a night. As the cycles are repeated, the duration of stages three and four decreases while REM increases.
What it means for athletes
So what happens if athletes don’t get enough sleep? Peter Walters identifies three areas that can be affected by a lack of sleep.
Cardiovascular performance. Cumulative sleep deprivation has been shown to reduce cardiovascular performance by 11%. So how much sleep do you have to miss before this begins to happen? Studies have shown that 30-36 hours of sleep deprivation can result in a loss of performance. If an athlete needs eight hours’ sleep yet only gets six, he/she will accumulate enough sleep debt in 15 days to significantly reduce their cardiovascular performance. Think about an athlete cramming for exams late into the night and getting up for an early morning training session. In just over two weeks his/her athletic performance could be impaired.
Information processing. During sleep our brain has a chance to sort, prioritise and file all the information we have taken in during the day. Mental functioning decreases nearly twice as rapidly as physical performance, so your athlete may feel physically fit but chances are he/she can’t recall the tactical information you gave them yesterday during practice, and they will struggle to make effective decisions during a match or event.
Emotional stability. Even minimal levels of sleep loss result in an increased perception of effort. Your athlete will feel more fatigued, his/her mood will have dropped and clearly they will not be in the type of mental state needed for a top performance.
What to do about it
After supplying an understanding of what happens during sleep and how a lack of sleep can have a negative impact on performance, Walters offers some guidelines to help your athlete achieve a good night’s sleep:
Identify and obtain the amount of sleep you need. The amount of sleep required varies considerably from person to person. You can identify how much sleep you need by answering the following questions:
- Do you frequently fall asleep if given a sleep opportunity (a sleep opportunity is defined as a quiet, dark environment for at least 10 minutes)?
- Do you usually need an alarm clock to wake you?
- Do you tend to catch up on sleep during the weekends?
- Once awake, do you feel tired most mornings?
- Do you frequently take naps during the day?
- When you can get it, do you consistently sleep more than 9.5 hours per night?
- Do you feel lethargic or slow throughout the day?
- Do you sleep longer during times of depression, anxiety and stress?
If an athlete answers yes to two or more of questions a-h, chances are he/she needs more sleep. If so, take the following steps.
Sensible steps everyone can take
Stabilise sleep for one week. Establish a consistent bedtime at which the athlete feels drowsy and can receive 10 hours of uninterrupted sleep. The athlete must go to bed within 30 minutes of the established bedtime.
Once stabilised, the athlete continues to go to bed at the established time but wakes up without the aid of an alarm clock. The amount of sleep is recorded and a nightly average is noted. This provides an indication of the athlete’s genetic sleep needs.
You can now make adjustments to the schedule but adjustments to earlier or later sleep should not exceed 30 minutes per night.
Keep a regular sleep schedule. It is important to establish a consistent sleep pattern. Changing your schedule for more than two days or sleeping more than an hour longer on weekends disrupts your body’s biological clock.
Create an optimal sleeping environment. Four factors help create this:
- Quiet. While we are able to adapt to some types of noise, we can still be disturbed when faced with noisy neighbours, loud traffic or roommates. Do-not-disturb signs, earplugs or a quiet policy may all help to ensure you are not disturbed during your sleep.
- Dark. An evolutionary signal to the brain that sleep should take place. I won’t labour the point.
- Cool. If a room is too hot or too cold it can increase the amount of time it takes to fall asleep and the number of sleep disruptions throughout the night. 65 degrees Fahrenheit has been suggested as the optimal room temperature, although personal preference may be different.
- Comfortable. Since humans shift their body position between 40-60 times per night, we need to have a good mattress and pillow, as well as plenty of room to manoeuvre.
(Strength and Conditioning Journal; Vol 24 No 2, pp 17-24)