There was a time, in my younger days, when I thought I would never walk during a run. I abandoned that philosophy about two-thirds of the way up a mountain in Slovenia, where I was competing in the 2010 World Mountain Running Championships. The course climbed a little over 4,000 feet in 7.5 relentless miles. During one particularly steep section, I finally gave in and started to walk. To my surprise, I didn’t lose any ground to the runners around me. Lesson learned, and I’ve been less dogmatic ever since.
I’m not alone, though. Even among serious trail runners, there’s sometimes a tendency to keep running at all costs, according to Jackson Brill, a Salomon-sponsored trail runner and graduate student in Rodger Kram’s Locomotion Laboratory at the University of Colorado. But when the hills get steep enough, walking becomes inevitable—and the decision about when to switch back and forth between gaits is among the key tactical choices trail competitors have to make. As it happens, Brill and his colleagues have been researching this problem for several years, and a pair of recent studies offer some interesting new insights. The bottom line: “Our research,” Brill says with tongue in cheek, “gives people permission to walk if they want.”
To understand the transition between running and walking, you have to start with a simpler question: is there really any difference between them on the steepest slopes? Under normal circumstances, one of the key distinctions between the two gaits is that you always have at least one foot on the ground when you’re walking, whereas you leave the ground between each step when you’re running. But that rule of thumb breaks down on steep hills: even when you’re “running,” you never fully lose contact with the ground.
Not convinced? Take a look at this 2015 video of former Locomotion Lab researcher Wouter Hoogkamer running on the world’s steepest treadmill, which is jury-rigged to go all the way up to 45 degrees (i.e. a 100 percent grade). He looks to me like he’s running, but he always has one foot on the ground.
Kram and his team broke out this same treadmill, which has been used for a bunch of previous uphill running research, for a study published over the summer in the European Journal of Applied Physiology. Led by first author Clarissa Whiting, a former Penn track star, the researchers recruited ten elite trail runners and had them run or walk on level ground and with the treadmill set to 30 degrees. That’s steep: typical gym treadmills only go up to about nine degrees, and black diamond ski runs tend to be around 30 degrees.
Sure enough, even though the runners always had one foot on the ground, there were distinctive differences between uphill running and walking. One clue was the stride pattern: on the slope, cadence was 40 percent quicker for running than walking, and feet stayed on the ground for 40 percent less time—a similar pattern, though less pronounced, to what you’d see on level ground.
But the smoking gun came from an accelerometer clipped to the subjects’ waistbands, which measured the rise and fall of their center of mass. On level ground, walking produces two distinct acceleration peaks, one as you land and one as you push off. Running, in contrast, is a series of hops from one leg to the next, producing just one acceleration peak as you land and take off. The accelerometers found exactly the same patterns on the inclined treadmill, confirming that steep uphill running really is running, and not just some sort of bouncy fast-walk.
Read more at: https://www.outsideonline.com