The Circadian Rhythm

  • Have you wondered why you feel sleepy at about 3pm each day?
  • If you ever stayed up all night at a party, did you notice having a “second wind” at various points?
  • Have you ever gone to bed really early to catch a morning flight, only to find you can’t sleep?
  •  Why do sportsmen and women go “off the boil” for a period in a match?
  • If you’ve ever experienced a mental block, did the answer come to you about 45 minutes later?

As you’re probably aware, human beings and all animals have body clocks.  These body clocks operate on a cycle of 24 hours and 15 minutes and are primarily governed by the rising and setting of the sun.  Throughout the day, there are plenty of other regular events (known as “Zeitgebers,” meaning “time givers”), discretely guiding our body clock.  These include when you eat your meals, when you go to work, take your exercise and so forth.

This cycle is known as the circadian rhythm and, within the 24 hour period, it operates in smaller cycles of 90 minutes (for adults).  Throughout the day it ticks along continuously, giving control and influence over many of our body’s functions, including hunger, thirst, urine production, alertness and many other functions.

Within each 90 minute cycle we have a peak of energy and a trough of fatigue.  Working in tandem with this cycle is a key element in overcoming insomnia.  If we chose or are compelled to ignore it, we are simply fighting our own natural cycle. 


Severn Sleep is the first dedicated CBTi sleep clinic in Shropshire, Powys and Worcestershire. Appointments are available at our clinics in Brecon, Ludlow, Shrewsbury and Malvern.  Alternatively, we offer appointments via Skype to clients across the UK and rest of the world.

Please Call Severn Sleep on: 07799 625628