Wrist motion rhythm phase shifts in travelers may differ from changes in time zones

Wrist motions (223-471)/5 min were measured during 17-32 days of continuous recordings made from human passengers as they traveled across zero to five time zones for business and pleasure. The travelers all exhibited daily cycles of activity and rest. The duration of daily activity, alpha, was 1.1 h less at the destination; the mean was 63 wrist motions/5 min less at the destination. Phase shifts of the daily rhythm (e.g., acrophases, 0.0 to 5.3 h) advanced or delayed in the direction expected from time zone changes. However, the magnitude of the phase shifts differed (e.g., as much as 2.3 h) from the expected changes because of transmeridian travel and there were phase shifts even when there was no change in time zone. Differences were observed in phase shifts assessed by different methodologies of determining phase (waveforms, onsets, offsets, acrophases).