What that means is that in order to ascend a slope most efficiently, you should choose trails that keep you between 20 degrees and 35 degrees. For reference, Kram notes that an average treadmill’s max incline is about 9 degrees. He explains how these finds can help you to select a route which, while longer in terms of actual distance, are actually quicker because of the difficulty in climbing the slope.
Kram summarized the findings via an analogy: “Imagine that you are standing in Colorado at a trailhead where the base elevation is 9,000 feet. Your friend challenges you to race to the summit of the mountain, which tops out at 12,280 feet, i.e. 1,000 meters of elevation gain. (Remember, one meter is about 3.28 feet.) There are several different trails that go to the summit. They are all pretty steep and some are extremely steep. One trail averages 10 degrees incline and the sign says it is 3.6 miles long. A second trail averages 30 degrees, but is only 1.25 miles long. A third trail averages 40 degrees, but only 1 mile long. To get to the summit the fastest, which trail should you choose and should you walk or run? Based on our research, we now know that choosing the second trail (30 degrees) and walking as fast as you can within your aerobic capacity is the fastest way to go.”
The study focused on a vertical rate of ascent of just over 1 foot per second, a pace that the high-level athletes could sustain aerobically during the testing. At that speed, walking used about nine percent less energy than running. So, sub-elite athletes can ascend on very steep uphills faster by walking rather than running.
The study examined 15 competitive mountain runners as they ran and walked on a custom-made treadmill, able to be set to an incline up to 45 degrees, at seven different angles ranging from 9 to 39 degrees. The treadmill speed was set so that the vertical rate of ascent was the same. Thus, the treadmill speeds were slower on the steeper angles. The athletes were unable to balance at angles above 40 degrees, suggesting a natural limit on the feasible slope for a VK competition.
“Very few people walk or run up such steep slopes, but by going to extremes, we broaden our horizons and investigate the limits to human performance,” said Kram.
As for amateur runners who aren’t planning to try a VK race anytime soon? “These findings indicate that you can still get a good aerobic workout simply by walking up very steep inclines,” Kram said.
So the next time you are out on a run, turn a corner on the trail or round a building to find a giant climb in front of you, remember that there are “hills” and there are “walking hills.” I’m a big fan of walking hills, because I frequently can still feel my heart pounding and my muscles working even though my breathing gets a bit of a break. It’s definitely still a challenge, but I’m ready to pick up the pace again at the summit.
Nicola Giovanelli, a visiting scholar from the University of Udine, Italy; Amanda Ortiz, a CU-Boulder cross-country runner and undergraduate student in the Department of Integrative Physiology; and Keely Henninger, who now works for Nike, co-authored the study. All three are competitive mountain runners and Ortiz was the 2013 Junior World Mountain Running champion.
The University of Colorado Boulder Undergraduate Research Science Training (BURST) and Undergraduate Research Opportunity Program (UROP) supported the research.
If you happen to live in the Boulder/Denver area and are interested in being a participant in future uphill running experiment, contact email@example.com.