The relationship between sleep and recovery after exercise, particularly relating to performance, is receiving more attention as the link between sleep cognitive function and metabolic function becomes better understood.
To fully understand the role that sleep has in the training process, and in particular during recovery, one needs to understand the different phases of sleep.
Stages of sleep
There are five distinct states of consciousness associated with sleep - stages 1, 2, 3, 4 and rapid eye movement (REM).
Stages 1 to 4 are often grouped together and referred to as non rapid eye movement sleep (NREM) (81). During the day, beta brainwaves dominate and reflect a mental state that is actively aware of the surroundings. As one lies down in preparation for sleep, beta waves are replaced by alpha waves. These are associated with a mental state of being awake yet relaxed.
After about five to 20 minutes of alpha brainwave activity, the mind is prepared to enter stage 1 of sleep. This first stage can last from 10 seconds up to 10 minutes and is defined by theta brainwaves.
During this stage, respiration becomes shallow and muscle relaxation occurs. The stage is also associated with the feeling of falling, and accompanied by a reflex response such as jerking of the arms or legs.
As the person progresses into stage two, the theta waves become intermingled with sleep spindles and K-complex waves. Sleep spindles, which can be measuring by EEG signals, arguably define the beginning of actual sleep since the person is oblivious to most external stimuli. This stage lasts from 10 to 20 minutes.
Stage 3 is defined by a combination of theta and delta brainwaves, with the delta brainwaves becoming more dominant. Stage 4, which is the deepest stage of sleep, is defined as the period when the theta waves disappear.
Stage 3 and stage 4 together are called slow wave sleep. During slow wave sleep, metabolic activity is at its lowest. Growth hormone is secreted during this phase so muscle repair and growth can be maximised.
After about 30 to 40 minutes of the delta sleep, the stage is reversed, reverting back to stage 3 and stage 4.
REM sleep begins after this step. During REM sleep there is an increase in blood pressure, body temperature, breathing rate, heart rate and blood flow. Even though the eyelids are closed the eyes move backwards and forwards. Dreams usually occur during REM sleep.
There is also a return of beta brainwaves, suggesting that the brain is more active. The cycling between the stages of sleep is repeated between four and six times a night with each cycle lasting about 90 minutes.
As the duration of the sleep increases (i.e. after a few cycles) the duration of stage 3 and stage 4 decreases, while REM sleep increases.
If sleep is disturbed before slow wave and REM sleep is achieved, the whole process restarts. It is known that disturbances in sleep (insufficient and poor quality, circadian rhythm disturbance) are the main factors that affect the restorative ability of sleep.
It has been recommended that athletes should have at least seven to nine hours of sleep a night.
Based on the understanding of sleep and how it contributes to recovery and restoration, there is reason to believe that “power naps” during the day will be beneficial for a rugby player.
Research has shown that “power naps”, defined as a brief period of daytime sleep lasting less than an hour, improves alertness, productivity and mood, and may contribute to consolidating learning and improved performance of tasks involving visual discrimination.
Practical guidelines for enhancing sleep are shown below. These guidelines become more relevant with travelling, as maintaining good quality sleep becomes a particular challenge with touring teams, particularly when time zones are crossed.
• identify your sleep requirements and try to get this amount daily
• develop a pattern of sleeping and waking times
• practice relaxation techniques before going to bed
• try to avoid worrying about anything before going to bed
• make the bedroom as dark as possible (use a mask if necessary)
• try to maintain a quiet environment (use ear plugs if necessary)
• use a bed that is at least 15 cm longer than the body
• maintain a cool environment within the bedroom
• keep your head cooler than your body
• if you do not fall asleep within 30 minutes, get out and do some relaxation work
• avoid ingesting high-protein meals, caffeine or alcohol in the few hours before going to bed.
This is an extract of Recovery techniques and practical guidelines by SA Rugby. For the full article click here.
Source: SA Rugby: Recovery techniques and practical guidelines by Mike I. Lambert and David Van Wyk; MRC/UCT Research Unit for Exercise Science and Sports Medicine.
(Health24, August 2011)