Athletes perform better in the afternoon after exposure to bright light, if they are morning people at least, write researchers at the Technical University of Munich in PLoS ONE. If you're a night bird, light treatment in the morning is not such an interesting proposition.
Exposure to bright light helps people who do shift work to perform better. [Ind Health. 2005 Jan; 43(1): 34-48.] You'd expect that exposure to light would also help athletes, but so far no convincing studies have been done. One study looked at whether bright light helped subjects to cycle faster, but the results were inconclusive. [Med Sci Sports Exerc. 2000 Feb;32(2):439-47.]
The researchers at the Technical University of Munich also looked at the effects of light on sports performance. They exposed their test subjects – 43 male students – to low light [230 lx] or bright light [4400 lx] for 160 minutes. For their experiment the researchers used HF3309 PL-L 36 W Philips EnergyLights. During the last 40 minutes of the exposure time, the students had to cycle as fast as they could.
The researchers also ascertained from the students whether they were morning or evening people. Morning people go to bed early and get up early; evening people go to bed late and often get up late too.
The experiment took place at 14.00. The evening people had been awake for less time at that point ["earlier"] than the morning people ["later"]. The figure below shows that the light treatment had an effect on the morning people – who had been up for longer – but not on the evening people.
kJBL = energy expenditure under bright light; kJDL – energy expenditure under low light.
"Although more studies are needed for a more detailed cost/benefit estimation of different bright light interventions on physical performance, our results indicate that we will in future be able to recommend tailored and optimally timed training sessions for individuals with different chronotypes", the researchers conclude.
PLoS One. 2012;7(7):e40655.