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Bright light and thermoregulatory responses to exercise
G Atkinson1, D Barr, N Chester
1Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom. G.atkinson@ljmu.ac.uk
International Journal of Sports Medicine
|November 9, 2007
Summary
Morning exercise in heat is less taxing when participants are exposed to evening bright light. This chronobiologically-based light schedule lowers core body temperature before and during exercise.
Area of Science:
- Chronobiology
- Exercise Physiology
- Thermoregulation
Background:
- Bright light exposure influences circadian rhythms and thermoregulation.
- Morning exercise in hot environments poses significant physiological challenges.
Purpose of the Study:
- To examine the effect of different bright light exposure schedules on thermoregulatory responses during morning exercise in the heat.
Main Methods:
- Six males performed 40-minute exercise bouts at 60% maximal oxygen uptake in a hot environment (31.4°C).
- Participants were exposed to bright light (10,000 lux) either from 22:00-23:00h (BT (low)) or 06:00-07:00h (BT (high)), with dim light (<50 lux) otherwise.
- Melatonin levels, core body temperature, mean skin temperature, and perceived exertion were measured.
Main Results:
- Evening bright light (BT (low)) suppressed melatonin and delayed the core temperature minimum.
- Core body temperature was lower before and during exercise in the BT (low) condition compared to BT (high).
- Mean skin temperature was higher during the initial phase of exercise in BT (low), and perceived exertion was attenuated.
Conclusions:
- A chronobiologically-informed light schedule, specifically evening bright light exposure, can effectively lower core body temperature before and during morning exercise in hot conditions.
- This strategy may mitigate physiological strain and improve exercise tolerance during morning workouts in the heat.
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