%A L. J. Crepeau %A J. D. Bullough %A M. G. Figueiro %A S. Porter %A M. S. Rea %T Lighting as a Circadian Rhythm-Entraining and Alertness-Enhancing Stimulus in the Submarine Environment %X The human brain can only accommodate a circadian rhythm that closely follows 24 hours. Thus, for a work schedule to meet the brain?s hard-wired requirement, it must employ a 24 hour-based program. However, the 6 hours on, 12 hours off (6/12) submarine watchstanding schedule creates an 18-hour ?day? that Submariners must follow. Clearly, the 6/12 schedule categorically fails to meet the brain?s operational design, and no schedule other than one tuned to the brain?s 24 hour rhythm can optimize performance. Providing Submariners with a 24 hour-based watchstanding schedule?combined with effective circadian entrainment techniques using carefully-timed exposure to light?would allow crewmembers to work at the peak of their daily performance cycle and acquire more restorative sleep. In the submarine environment, where access to natural light is absent, electric lighting can play an important role in actively entraining?and closely maintaining?circadian regulation. Another area that is likely to have particular importance in the submarine environment is the potential effect of light to help restore or maintain alertness. %D 2006 %K circadian, alertness, melatonin, lighting, spectrum, intensity, psychophysics %I Naval Undersea Warfare Center %L cogprints6574