The aims of this study are to compare 3 different treatments for circadian adjustment to a laboratory protocol which will mimic westward air travel across 8 time zones. One treatment will involve simply following the new schedule for 3 days. Another treatment will also involve exposure to bright light for 1 hour per day. A third treatment will involve exposure to bright light + exercise for 1 hour per day + consuming a melatonin tablet. Adjustment to the shifted schedule will be assessed by comparing measures of sleep, mood, mental performance, physical performance, and timing of melatonin across the 3 treatment conditions.

Design Overview. Following a 1 week home baseline, N=36 young adults will spend 6 days in the laboratory (Figure 3 and Table 1). Following am 8 h baseline polysomnographic recording (PSG) on Night 1, participants will undergo a 26 h baseline circadian assessment via an ultrashort sleep-wake protocol involving 2 h wake intervals and 1 h sleep intervals, repeated throughout the protocol. Following baseline circadian assessment, participants will be placed on a 16 h wake-8 h sleep schedule in which the wake-sleep and light-dark schedule is delayed 8 h for 3 days (analogous to traveling 8 time zones west). Participants will be randomized to one of 3 treatments (n=12 per treatment) administered each of the 3 days of the shifted schedule: (1) placebo control, (2) bright light, and (3) bright light + exercise + melatonin. PSG recording will occur on the last night of the shifted schedule, followed by an end-of-study 26 h ultrashort sleep wake schedule. On baseline Day 1 and Days 2-3 of the shifted schedule, sleepiness, mood, and mental performance will be assessed every 3 h during wake. During all four 8 h sleep periods, sleep will also be recorded with the Z-machine, which assesses sleep stages from 3 EEG electrodes. During the ultrashort sleep-wake schedules, mental performance, physiological performance, urinary aMT6s, mood, and sleepiness will be measured around-the-clock.

Inclusion Criteria:

1. age 18-45 years
2. At least moderate level of habitual physical activity (twice per week, 20 min of aerobic exercise at 60% of maximal effort or higher

Exclusion Criteria:

(1)Having more than one risk factor for coronary artery disease: (2) having any symptom or sign of cardiopulmonary disease; (3) recent shift-work experience (previous 2 months) or travel across multiple time zones (previous 4 weeks); (4) having an abnormal sleep-wake schedule (i.e., reported bedtime before 9:00 pm or after 2:00 am; wake time before 5:00 am or after 10:00 am); (5) being an extreme night owl or morning lark, as assessed by the Horne-Ostberg Mornngness-Eveningness Scale;70 (6) having a high risk sleep apnea or another sleep disorder; (7) depressed mood [Center for Epidemiologic Studies-Depression Scale (CES-D) > 16];71 (7) use of medications likely to distort melatonin excretion or cardiovascular responses to exercise; (8) use of sleeping pills more than 1 night per week; (9) having high sensitivity to light; (10) abuse of alcohol or drugs (amount per week; related problems such as missing work); (11) any physical or mental health condition that would contraindicate participation in exercise or other rigors of the experiment.

None. We will only share mean data which are de-identified

Participants are informed that we are exploring different types of stimuli (including exercise, melatonin, and light) to help adjust to simulated jet lag.