Circadian period and rhythm power across the three shift work-like schedules. Mean (A) period and (B) rhythm power during the phases of the behavioural intervention in the control, Fwd, Bck and Alt groups. LD1 refers to the initial period in a 12:12 LD cycle, SW for the last 3 weeks in under the appropriate shift work protocol, DD for constant darkness following the shift work protocol and LD2 for the 12:12 LD cycle at the conclusion of circadian rhythm monitoring. ** represents P < 0.01, * P < 0.05 compared to the initial LD values for that shift work group (Bonferroni post hoc test, # P < 0.05 compared to corresponding value for the control group (Tukey HSD test). N = 8 for each group.