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.
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.