Accession Number:

ADA458153

Title:

In Search of Circasemidian Rhythms

Descriptive Note:

Technical rept. for 1 Apr 2004-30 Jan 2005

Corporate Author:

AIR FORCE RESEARCH LAB BROOKS AFB TX HUMAN EFFECTIVENESS DIR/BIODYNAMICS AND PROTECTION DIV

Personal Author(s):

Report Date:

2006-11-01

Pagination or Media Count:

27.0

Abstract:

There is controversy over the existence of physiological or behavioral circasemidian 12-hour period rhythms. However, a number of reports have shown a circasemidian error pattern in industrial and transportation environments and a circasemidian pattern in body temperature. To help us quantify the effects of fatigue, we hypothesized that body temperature, subjective sleepiness, simple response time and working memory speed would oscillate with a period of 12 hours the circasemidian frequency and that the parameter values describing the circasemidian oscillations of the measures would differ across genders and age groups. Measurements were acquired from 37 male and female subjects at half hourly intervals from 0700h to 1900h in constant conditions. Circasemidian cosine curves were fitted to the data of individual subjects by the least squares method. A statistically-significant, 12-hour pattern was found for body temperature and for subjective sleepiness, but not for simple response time or working memory speed. No differences were found with respect to gender or age group. Body temperature peaked at 1649h and sleepiness peaked at 1740h. Considering the large numbers of field observations of a two-peak pattern in errors and accidents, the failure to detect a circasemidian rhythmicity in task performance was attributed to the nature of task, itself. Future investigations should attempt to replicate our findings, acquire 24 hday body temperature data, combine circasemidian with circadian cosinor estimates, determine which laboratory tasks display a circasemidian rhythmicity, try to determine why only some tasks may display that rhythmicity, and consider models other than the cosine curve.

Subject Categories:

  • Anatomy and Physiology
  • Stress Physiology
  • Statistics and Probability

Distribution Statement:

APPROVED FOR PUBLIC RELEASE