The Scientific Reason Behind Why Night Running Feels So Much Harder

With the end of daylight savings and winter firmly upon us, most of us tread to the office only to watch the sun begin its descent from our desks. Few things are as upsetting as bidding farewell to nature’s light source before you’ve even had a chance to clock off and enjoy it, but when it comes to exercise and fitness, there are only so many hours in a day. Not ones to roll over and give up on our fitness goals and those resolutions cast in the early hours of the New Year, we turn to night running, logging miles under the blanket of darkness. 

For those who profane at early mornings and running on an empty stomach, the evening run can be something of a welcome substitute. But if you’ve ever found yourself out of breath and profusely sweating, only to look down at your watch and find you’re running slower than normal, there might just be a scientific reason as to why your perceived effort outweighs your pace. 

According to a recent study conducted by researchers at Sweden’s KTH Royal Institute of Technology and published in the European Journal of Applied Psychology, running in the dark is actually harder. Researchers had 15 volunteers do a series of ten-minute treadmill walks in four conditions: with and without a 25kg pack, and with and without a blindfold on. The treadmill was set at a comfortable pace of 30 minutes per mile, and soldiers also received a laser warning system should they be about to fall off the back of the treadmill. 

Researchers discovered that oxygen use, breathing, and heart rate all increased substantially when wearing the heavy pack. Interestingly though, these factors also increased by nearly the same amount when adding a blindfold. While the weighted backpack increased oxygen consumption by 20 per cent, wearing a blindfold also saw oxygen consumption increase by 19 per cent. It turns out that walking with a blindfold took as much extra effort as walking with a 25kg pack. 

It might sound strange that a blindfold could increase exertion – or at least perceived exertion – in such a way, but researchers noted that when subjects were blindfolded, they were forced to adjust their strides. Steps got 11 per cent shorter and 6 per cent wider, and they also lifted their feet 18 per cent higher. Given that it was on a flat treadmill, this change in stride was purely instinctual. 

While walking is different from running and it’s worth noting that a blindfold is more disruptive than simply running in darkness, it bears keeping in mind the findings from the study which suggest that similar mechanisms are at work when pounding the pavement in the dark hours of the evening. 

Ultimately, your perceived exertion when running in the dark will significantly outweigh – in most cases, anyway – your actual pace. Your times will likely be far slower than if you were running during the day, simply as a result of having to adjust to your surroundings and lack of vision. But at the end of the day, this is the body’s instinctive response and we’d take a slower Strava segment over tripping and falling flat on our face any day.