INTRODUCTION: Arguments against counterclockwise shift schedules, such as those used in air traffic control, are prevalent in the literature; however, few studies have examined direction of rotation in rapidly rotating schedules. The present study directly compared clockwise (CW) and counterclockwise (CCW) rapidly rotating shiftwork schedules on measures of complex and vigilance task performance.
METHODS: Participants (n = 28) worked day shifts for the first week of the study (0800-1600 h), followed by 2 wk of either a CW (n = 14) or CCW (n = 14) shiftwork schedule. Participants completed three 1.5-h sessions on the Multiple Task Performance Battery (MTPB) on each shift. Each session contained active- and passive-task components. In addition, participants completed a 0.5-h Bakan Vigilance Test at the beginning and end of each shift.
RESULTS: A three-way, rotation condition by shift by session interaction (F (8,19) = 3.0, p < 0.05) for the active task composite scores and a rotation condition by shift interaction (F (4,23) = 6.2, p < 0.05) for the Bakan Vigilance Task indicated that effects of rotation condition were modulated by shift type, such that on particular shifts, performance in the CCW rotation was actually better than in the CW rotation.
DISCUSSION: These data do not support the hypothesis that a CW rotation will result in better outcomes on complex or vigilance task performance. The results of this study indicate that two problem areas in both CW and CCW rapidly rotating shift schedules are early morning and midnight shifts.
