Adjustment of the diurnal rhythm in body temperature by a transposition across the longitudes with a moderate speed.

Abstract

Diurnal rhythm in body temperature and heart rate of 12 healthy athletes were recorded during a TransPacific voyage from Japan to the west coast of the United States. The speed of the ship was 14-16 knots which caused shortening of the actual length of a day by 32 minutes. The ratio of the lag of change in diurnal body temperature rhythm did not seem to be constant throughout the voyage. The adjustment of the rhythm to a new local time seemed to occur slowly during the first few days but fairly fast after the second week on the ship. During the voyage the rhythm was approximately 2 hours behind the typical temperature rhythm of the local time, and the rhythm could follow the new environmental routines in 3 or 4 days after arrival in USA. The results obtained suggest that the intrinsic biological rhythm formed during a longer period of time resists greatly distortion by a new environmental rhythm even with moderate speeds in trans·position. The diurnal rhythm in body function appears to adapt fairly rapidly to new environmental routines, although there are some literatures showing that the rhythm is hardly disturbed by a displacement or an inversion of the daily routines of living 1 ' 2 '· Sasaki 3 ' reported that there was apparently no difference between the diurnal change in body temperature and the external periodicity of living with a slower transposition across the longitudes, but with a faster speed of transposition which resulted in change of a day by approximately 30 minutes one could see a disparity between the external periodicity and the diurnal rhythm. In this latter case, apparently three days seem to be neces­ sary before the subjects' diurnal body rhythm is adjusted to the new environmental routine. Data observed for quickest transposition by a jet flight