Ultradian rhythms are recurrent periods or cycles repeated throughout a 24-hour circadian day. What the article is talking about is called Basic Rest Activity

Ultradian rhythms are recurrent periods or cycles repeated throughout a 24-hour circadian day. What the article is talking about is called Basic Rest Activity Cycle. Don't know much about if there is much or any scientific support for it. http://en.wikipedia.org/wiki/Basic_rest_activity_cycle http://en.wikipedia.org/wiki/Basic_rest_activity_cycle http://en.wikipedia.org/wiki/Ultradian http://en.wikipedia.org/wiki/Ultradian