infradian and ultradian rhythms

• ultradian rhythms: rhythms that span a period of less than one day
• ultradian rhythm example 1: sleep cycle

  • 4 stages, repeats every 90 to 100 minutes, can be recorded with EEGs
  • stage 1 - light sleep
  • stage 2 - breathing pattern + heart rate slow
  • stage 3 - deep sleep begins
  • stage 4 - very deep sleep
  • stage 5 - rapid eye movement (REM)
• ultradian rhythm example 2: basic rest activity cycle (BRAC)

  • 90 minute cycle
  • human mind can concentrate for 90 minutes but then needs a rest period of 90 minutes
• infradian rhythms: rhythm that is greater than 24 horus
• infradian rhythm examples

  • weekly rhythms: male testosterone levels (elevated on the weekend), blood pressure + heart rates
  • monthly rhythms: human menstrual cycle (23 to 36 days, regulated by hormones oestrogen and progesterone)
  • annual rhythms: seasonal affective disorder
• (+) research support for basic rest activity cycle

  E: study conducted on elite athletes and musicians found that they would out perform their trainers after training for 90 minutes then resting (eating and sleeping) for 90 minutes

  E: this has also contributed to real world applications as professional athletes can create training plans in order to maximise performance through utilising the BRAC

  L: suggests there is a BRAC lasting 90 minutes that can be used to enhance performance, providing support for ultradian rhythms
• (-) issues with sleep studies limit its support for ultradian rhythms

  E: in sleep studies participants ould have had their sleep monitored by an EEG

  E: which could have potentially disrupted their usual sleep pattern, thus lowering the validity of these studies

  L: thus findings of these studies cannot be applied to those not sleeping in these specific conditions and so can't be used as support for ultradian rhythms
• (+) stages in menstrual cycle can influence mate choices

  E: a study found that women prefer men with softer, more caring facial features when not ovulating but a sharper jawline and facial hair when ovulating

  E: could be because they look for a caring man in a long term partner but prefer high testosterone and strong genes when looking for a mating partner

  L: provides support for the different stages of the menstrual cycle and thus the menstrual cycle as an infradian rhythm