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Light Exposure and Physical Performance

21 Sep 2015
Randall Cooper
Athletic performance varies over the course of each day, with peak physical performance usually occurring for most people in the late afternoon or early evening. This shift in peak performance is primarily governed by a person’s circadian rhythm, a component of the internal body clock, which regulates physical, mental, and behavioural changes over a 24-hour cycle. But what can you do if you have a sporting event in the evening? Can you shift your body clock so that you peak at the right time?

Our circadian rhythm is influenced by exposure to light. When it get’s dark, a group of nerves near the optic nerve in our brain known as the suprachiasmatic nucleus, or SCN, relay information to the brain to produce more melatonin, so you feel drowsy and ready for bed. If you’ve got a sporting event in the evening this is not ideal.

A recent study published in the Scandinavian Journal of Medicine and Science in Sports (2) looked into the effect of bright light (4420 lx) or moderate light (230 lx) exposure on a 40 minute cycling time trial performance in a randomised cross over design. The durations of light exposure were 120 minutes before and during exercise, 60 minutes before and during exercise, or only 60 minutes before exercise. It would have been good for the authors to include a control group in study, but this was not done.

Illuminance Examples


Surfaces illuminated by:

50 lx

Family living room lights

320-500 lx

Office lighting

1000 lx

Overcast day, typical TV studio lighting

10,000 – 25,000

Full daylight (not direct sun)

The cycling time trial was conducted at each individual’s chronotype, a calculation on when each individual will naturally fall asleep (using the Munich Chronotype Questionnaire). There was a statistically significant dose-response relationship between light exposure and time trial performance, with the 2 hour bright light cohort performing better (527 kJ) than the 2 hour medium light exposure group (512 kJ). There weren’t significant differences between groups in all 60 minutes groups.

The authors concluded that long exposure (2 hours) to bright light is an effective tool to improve athletic performance in a 40-minute exercise session in the late evening. In other studies bright light exposure in the late evening has been shown to improve alertness and cognitive performance (3,4) and delay circadian rhythm, so bright light exposure will assist in both physical and mental performance.

The application of this research mainly applies to elite athletes. As many sporting events now take place in the evening to gain maximum television exposure, athletes can find themselves competing in important events at unfavourable times. Bright light exposure may help athletes adjust better to these situations.

For recreational athletes, this research highlights the importance and influence of circadian rhythm and light exposure on physical and mental performance. It’s worth considering if you do play sport in the evening, or if you’re crossing time zones to compete in an event.


  1. Reilly T, Waterhouse J. Sports performance: is there evidence that the body clock plays a role? Eur J Appl Physiol 2009: 106: 321–332 
  1. Knaier, R., Meister, S., Aeschbacher, T., Gemperle, D., Rossmeissl, A., Cajochen, C. and Schmidt-Trucksäss, A. (2015), Dose–response relationship between light exposure and cycling performance. Scandinavian Journal of Medicine & Science in Sports. doi: 10.1111/sms.12535
  1. Winkler D, Pjrek E, Iwaki R, Kasper S. Treatment of seasonal affective disorder. Expert Rev Neurother 2006: 6: 1039–1048.
  1. Rastad C, Ulfberg J, Lindberg P. Light room therapy effective in mild forms of seasonal affective disorder – a randomised controlled study. J Affect Disord 2008: 108: 291–296.

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