Running in the dark is sometimes unpleasant, but does it slow you down or make you move faster? Peta Bee heads to the dark side to find out

‘Dark’ races can get filled well ahead of deadline, and more events spring up by the month. Organisers might claim it is more fun to run at night, but not everyone agrees. Among athletes, opinion is divided as to whether darkness is a help or hindrance in the winter months. So what do the scientists say?

Fewer distractions

Scientists are beginning to understand more about how the mind adjusts to night running and why it might even give us a psychological boost. With less to look at, darkness certainly provides fewer distractions.

In a study at the University of Essex Human Performance Unit, the triathlon coach and sports scientist Dave Parry examined whether speed increases in certain environments are all in the mind. His results could explain why some people feel they are changing their usual speed at night.

Optical flow

To test his theory, Parry put cyclists on indoor bikes and had them perform a 20km time-trial ride and then three more over several days in which they aimed to match that first time. During the trial, subjects watched a video of a virtual road. What they didn’t know was that Parry was manipulating levels of ‘optical flow’, the visual sensation of moving through an environment, by altering the ‘speed’ of the projected road. His results, published in the Journal of Sport and Exercise Physiology, found that exercisers felt they were moving faster when the scenery was going by 15% faster than they were actually travelling.

Altered perception

When passing scenery that had been slowed, their perceived rate of effort and speed was lower. This is relevant, because we gauge speed by the movement of the scenery both near and far away – distant objects appear to move more slowly, while we appear to breeze past the nearby street lamps.

According to Parry, ‘Running in the dark alters your perception of speed. Because objects further away aren’t as visible and you only have close-by objects like trees and road signs to use as reference, you get a greater sense of speed, and potentially effort, compared with running during the day.’

In reality, of course, you are running no faster (or slower) than normal. It just feels like you are.