SLEEP CY­CLE

Runner's World (UK) - - Train While Your Sleep -

A sleep cy­cle takes 90 mins. The stages alternate be­tween REM (rapid eye move­ment) and NREM (non-rapid eye move­ment).

NREM

As we fall asleep, we en­ter NREM, ac­count­ing for 75 per cent of a night’s sleep. This com­prises:

N1: This is where you’re be­tween be­ing awake and fall­ing asleep – light sleep.

N2: The on­set of sleep; you be­come disen­gaged from your sur­round­ings. Breath­ing and heart rate are reg­u­lar; body tem­per­a­ture drops.

N3: The deep­est, most restora­tive sleep, blood pres­sure drops; breath­ing is slower; mus­cles re­lax; blood sup­ply to your mus­cles in­creases; tis­sue re­pair oc­curs.

REM

REM ac­counts for the other 25 per cent; it be­gins about 90 mins af­ter you fall asleep and re­curs roughly ev­ery 90 min­utes there­after; the pe­ri­ods grow longer later in the night. This pe­riod sup­ports op­ti­mum day­time per­for­mance and is when the brain is most ac­tive (most dreams oc­cur), and your body is im­mo­bile as your mus­cles are ‘ turned off’.

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