The effects of silmulated jet lag on sleep, exercise and cognitive performance in male athletes
Goldin, Tamar Shira
Jet lag results in a temporary mismatch between the body‟s internal clock and local time cues. Travel across time zones negatively alters the sleep-wake cycle, body temperature, psychological status, cognitive performance, and athletic ability of the traveller. I was interested in investigating the impact of a laboratory simulated six hour phase advance shift in the sleep-wake cycle on core body temperature, sleep patterns, mood, cognitive and athletic performance in 10 male athletes (age, 23.8 + 3.2 years; Mean + SD). The athletes were studied over two randomized weekends; a local time (“home” weekend) and a six hour phase advance shift (“away” weekend). In the six hour phase advance shift (“away”) weekend, all sleep-wake times, meal times, exercise tests, and cognitive tests were advanced by six hours. Body temperature, objective sleep parameters, subjective sleepiness, mood states, cognitive performance (reaction time), and athletic performance were measured over both weekends. Physical measures of athletic performance such as muscular strength, abdominal muscular endurance, flexibility, anaerobic ability, hand grip strength, and aerobic performance were measured. On both weekends, the results showed a circadian rhythm in body temperature; however, body temperature rhythm was significantly disrupted after the phase shift (p<0.05). After the phase shift, a significant decrease in total sleep time, percentage of rapid eye movement sleep, sleep efficiency, and increased time awake during sleep was observed (p<0.05). There was a significant decrease in muscular strength, abdominal muscular endurance, and anaerobic ability after the phase advance shift (p<0.05). Simple reaction time, a measure of cognitive performance, was not affected after the phase shift (p>0.05). The six hour phase shift resulted in altered mood states and elevated subjective daytime sleepiness (p<0.05). To conclude, a six hour phase advance shift of the sleep-wake cycle impaired sleep, anaerobic athletic performance and mood which may be problematic for athletes travelling across time zones.