The scientific reason why running at night is so much harder


There are only a limited number of hours in a day, but for those who have to pound the pavement in the evening, the race is infinitely more difficult.

With DST and winter time ending, most of us head to the office only to watch the sun begin its descent from our desks. Few things are as heartbreaking as saying goodbye to nature’s source of light before you’ve even had a chance to stop and enjoy it, but when it comes to exercise and fitness, there are only a limited number of hours in a day. Not one to turn around and abandon our fitness goals and those early New Year’s resolutions, we turn to running at night, logging miles under the cover of darkness.

For those who profane early in the morning and run on an empty stomach, the evening run can be a welcome substitute. But if you’ve ever found yourself gasping for breath and sweating profusely, only to look at your watch and find that you’re running slower than normal, there may be a scientific reason why your perceived exertion outweighs your your pace.

According to a recent study conducted by researchers at the Royal Swedish Institute of Technology KTH and published in the European Journal of Applied Psychology, running in the dark is actually more difficult. The researchers asked 15 volunteers to do a series of ten-minute treadmill walks under four conditions: with and without a 25 kg bag, and with and without a blindfold. The treadmill was set at a comfortable pace of 30 minutes per mile, and soldiers were also given a laser warning system if they were about to fall off the back of the treadmill.

The researchers found that oxygen consumption, respiration, and heart rate increased significantly while carrying the heavy bag. Interestingly though, these factors also increased by almost the same amount when adding a blindfold. While the weighted backpack increased oxygen consumption by 20%, wearing a blindfold also increased oxygen consumption by 19%. It turns out that walking with a blindfold on took just as much extra effort as walking with a 25kg bag.

It might seem odd that a blindfold could increase exertion — or at least perceived exertion — in this way, but the researchers noted that when subjects were blindfolded, they were forced to adjust their strides. The steps became 11% shorter and 6% wider, and they also lifted their feet 18% higher. Considering it was on a flat treadmill, this change in stride was purely instinctive.

Although walking is different from running and it should be noted that a blindfold is more disruptive than just running in the dark, it is worth keeping in mind the study results which suggest that similar mechanisms are at work when pounding the pavement during the dark hours of the evening.

In the end, your perceived effort when running in the dark will – in most cases, dramatically outweigh your actual pace. Your times will likely be much slower than if you were running during the day, simply because you have to adapt to your surroundings and your lack of vision. But ultimately it’s the body’s instinctive response and we’d take a slower Strava segment to stumble and fall flat on our face any day.

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