The Effects of 'Jet-Lag' on Exercise Performance,
ARMY RESEARCH INST OF ENVIRONMENTAL MEDICINE NATICK MA
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The behavioral and cognitive changes resulting from crossing multiple time zones are well known. Amongst the symptoms usually observed are fatigue and lassitude which suggests that exercise capacity may also be altered. Yet no controlled experimental studies have been reported of the effect of transcontinental flights on either athletic or occupational physical performance. Because of the obvious application to military deployment, a study was conducted Wright, et al 24 which assessed physical exercise capacity and performance in eighty one soldiers five days before and five days immediately after crossing six time zones by jet aircraft. Measures of aerobic and anaerobic capacity and muscle strength were made as well as several physical performance tasks. Aerobic capacity as measured by treadmill maximal oxygen uptake was unaltered. Dynamic strength and endurance of the elbow flexors muscles declined significantly while isometric strength of upper torso, trunk and leg muscle groups was unchanged. Performance times increased after the trans-continental flight for a 270 meter sprint, 2.8 kilometer run and a 110 meter lift and carry while no alteration was observed in a 6.5 meter rope climb. These observations suggest that certain physical capacities are affected by multiple time zone translocation but they may be due to sleep loss induced fatigue rather than biorhythm disruption of physiological mechanisms. The specific mechanisms, duration, magnitude and ultimate impact of these effects on actual physical performance remain to be explored.
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