Evening light improves morning cycling performance

More research has just been published showing how light can be used to gain a sporting advantage.

It's well-known that light is just about the most important factor in controlling our body clock and regulating our circadian rhythms. Depending when you switch on, bright light can be used to phase delay or phase advance circadian rhythms - this is the theory behind scheduled light therapy for jet lag. The Research Institute for Sport and Exercise Sciences at Liverpool John Moores University wanted to take things a step further and find out if shifting circadian rhythms with light could impact on sports performance.

Temperature is a relatively simple thing to monitor and is a good indicator of the state of your body clock. If you monitor core body temperature (CBT) over 24 hours, it typically dips to its lowest a few hours before waking up. Light therapy before this will create a phase delay, i.e. the next low CBT point will occur later. Distance cycling and running events are often scheduled for the morning to minimise 'thermal stress' on the athletes, the relatively low CBT helping to balance out the impact of exercise and/or warm conditions. So would it make a difference if you could shift circadian rhythms prior to an event?

Eight healthy, sporty men visited the Institute's specialised lab to familiarise themselves with the equipment and to take part in a baseline tests (e.g. heart rate, blood pressure, oxygen consumption with exercise). The experimental part of study involved two overnight stays roughly a week apart; subjects arrived at 7:30pm and either spent the whole evening relaxing in very low light or had a 30-minute burst of bright light from Lumie lights around an hour before bed. In the morning, they did some warm-up cycling followed by a 10km time trial... all in a 35degC 60% humidity chamber! CBT was monitored the whole time.

Bright light was found to shift minimum CBT by an average of 1.75 hours, from around 02:45 to 04:30. CBT was lower (only fractionally - body temperature changes can't be huge!) at this point and remained consistently lower than the non-light treatment during the warm-up. The gap widened significantly as the time trial progressed in these very hot conditions. And performance? Cyclists that had been exposed to bright light completed the 10km in 18:40 minutes, 1:26 minutes faster than those that hadn't!

Low CBT prior to and during exercise is important to athletes and many use 'pre-cooling' techniques such as cold drinks and rooms, cooling vests, cold packs and splashing with cold water. These have been shown to improve time trial performance by up to 15% (cold drinks) and so the 7.2% improvement in this study is pretty impressive.

It was only eight people but this study does suggest that even a 30-minute bright light session the night before an event could make a big difference. If you want to conduct your own experiment, check out any of our bright lights; we no longer make the model used in this study but Zest is very similar and small enough to take to with you when you're competing. Stay cool!

Download full research article

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October 09 2014

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