Author: Horsman, Sarah
About Author: Warden of Sheldon

A user's guide to the innate rhythms of the human body and mind

Original Article created on 11 Jun 2017
Last edited on 10 May 2021
Approved by Moderator not yet
Publish date: 12 Jun 2017


Why do we need to understand the BRAC (Basic Rest Activity Cycle)?

  • Essential information for getting well if we wind up exhausted/knackered
  • Very useful any time we are convalescing
  • Pretty handy in the general life skills tool kit

We are not extractor fans. We are not built to just keep running at a steady pace hour after hour. Human minds and bodies have an inbuilt rhythm. This is the Basic Rest Activity Cycle (also known as the Ultradian* Rhythm).

Key BRAC facts

  • We oscillate between two states
    • Up time = outer function, the ability to give into our commitments of love and work, sympathetic nervous system dominance, feeling energised
    • Down time = inner function, rest, healing, growth and repair, laying down of long term memories, making of meaning, replenishment of energy**, parasympathetic nervous system dominance
  • The rhythm is relatively subtle and for survival reasons it has to be easily overridden by stress – if our threat detector has been activated then we are in high vigilance and we don’t take the risk of down time

How to skip/override down time

If there is an urgent threat or demand to be handled then we automatically override the down time, and that's fine when needed. But these strategies can also become bad habits and we don’t notice we’re misusing the override capacity. Each of the strategies generates a short term energy boost to prolong the up time.

  • Willpower (trying harder generates adrenaline)
  • Drugs’ – typically caffeine or sugar
  • Overbreathing*** generated by any strong emotion like fear or anger

Some of the signs of moving from up time to down time

  • Concentration goes off, silly slips (spelling, sums, finding words), can’t remember what you’ve just read
  • Emotions slightly more labile (less stable) - maybe suddenly a little teary or fed up for no particular reason
  • Tired, yawning
  • Restless, fidgety, want to move, get fresh air, have a change
  • Hungry, thirsty, need the loo
  • (For smokers – want to light up)

Also need to know ...

When we’re in healthy function a cycle is usually roughly 90 minutes up time, 20 minutes down time. At the end of the down time we are naturally re-energised, focused and ready to concentrate again.

We ‘tune in’ to and harmonise our rhythms with the people we share our lives closely with, (psychosocial entrainment). Eating, exercising and resting together in a domestic environment are particularly strong harmonisers, but we also pick up signals from those in our working environment. Being harmonised with someone with a healthy pattern can help us with our own balance, but we can also get dragged into someone else's unhealthy rhythms. 

When we’re exhausted we feel ‘tired but wired’. Every time the body-mind signals for down time we try harder, pull out the willpower stops, reach for the drugs, do whatever it takes to kick in some more adrenaline. But we are failing to replenish our energy supplies naturally and the adrenaline makes us jittery and unable to rest. A nasty vicious cycle.

The more exhausted we are the shorter the up time and the longer the down time. We can end up feeling permanently tired and there is little or no real energy available - physical, emotional, concentration or motivation. 


*Circadian ‘circa dies’ about a day, sleep/wake rhythm. Ultradian ‘ultra dies’ more frequent than daily = basic rest activity cycle.

**phosphorylation of ADP to ATP - the basic molecules of energy at a cellular level in the mitochondria

*** Overbreathing or hyperventilation activates the sympathetic nervous system and release of adrenaline in the short term, but depletes energy reserves in the long term