The Optimal Slope for Running Uphill

There is an obscure, but cool-sounding, type of race called a “vertical kilometre,” where the idea is to race uphill as fast as possible until you gain 1,000 metres of elevation. The current men’s record is 29:42, set on a course in Switzerland that is 1,920 metres long with an average slope of 27.5 degrees; the women’s record is 36:04.

The question is: what type of course is best for such races (or, more generally, for gaining elevation as quickly as possible)? Should you find a relatively gentle slope where you can go fast? Or a steep slope where your progress will be slow and difficult, but you’ll gain lots of elevation with each step? Where is the sweet spot?

That’s what researchers at the University of Colorado in America wanted to find out in a study just published in the Journal of Applied Physiology. The team of Nicola Giovanelli, Amanda Ortiz, Keely Henninger, and Rodger Kram jerry-rigged a treadmill to be able to reach a slope of 45 degrees. For context, a typical gym treadmill can reach about 9 degrees, while a black diamond ski run is about 25 degrees. (In practice, runners had a hard time balancing at 45 degrees, so the study only went up to 39.2 degrees.)

The subjects—15 experienced mountain runners—ran and walked on the treadmill for five minutes at a time at seven different angles between 9.4 degrees and 39.2 degrees. The speed of the treadmill belt was adjusted so that they were always gaining vertical elevation at 0.35 metres per second (slightly slower than both the men’s and women’s vertical kilometre records, which correspond to 0.56 and 0.46 metres per second). That meant the treadmill belt was moving fairly fast at the gentle slopes, and very slowly at the steepest slopes.

Here’s what the energy expenditure looked like:

At the flattest angle, which is equivalent to the steepest angle most gym treadmills can reach, running is more efficient than walking. But for all angles above 15 degrees, walking was actually more efficient than running. The sweet spot with the lowest energy expenditure was between about 20 and 35 degrees—which puts the 27.5-degree angle of the course where the record was set perfectly in the middle.

Of course, these findings are specific to the rate of vertical ascent tested, but they give some idea of the energy involved in going uphill, with a surprising edge for walking. Or perhaps it’s not all that surprising.

The first time I competed at the World Mountain Running Championships, I remember feeling completely demoralised when I had to walk on a particularly steep section. Then I realised that I wasn’t actually losing any ground to the people around me, even though they were running.

Interestingly, even though walking was clearly more efficient than running at most angles, the subjects in the study still said they’d prefer to alternate between walking and running. I asked Rodger Kram whether that’s an error on their parts, not realising that walking is more efficient, or whether there might be some benefits to switching up which muscles you’re using periodically.

His answer was “the latter for sure.” We’re very good at sensing what feels easiest, so it pays to trust your instincts about what feels easiest.

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