This is a pop quiz. Ready? Here’s the question: When running on a treadmill, how can you adjust the treadmill to make it equivalent to running outdoors?
Don’t congratulate yourself too fast, at least not if you gave this common answer of setting the treadmill’s incline at 1%. Even though this method has been oft-repeated through the years, it turns out to be mostly urban myth. The correct answer can be found in a wonderful treadmill-running blog recently posted by Casey Kerrigan, founder and president of Oesh Shoes.
Kerrigan, a Harvard Medical School graduate with a masters in physical rehabilitation, spent many years doing research into walking and running biomechanics. When one study indicated that high-heeled shoes can lead to knee arthritis among women, she began looking into healthier designs. Several years ago, she left a tenured position at the University of Virginia, U.S., to launch Oesh, which makes running and walking shoes for women only.
In her blog, Kerrigan notes that the widely quoted 1% rule represents an oversimplification of the original investigation by England’s Andrew Jones. Jones is the well-respected exercise physiologist who tested Paula Radcliffe during her career, and recently pioneered work with beetroot juice as a performance-enhancer.
In his famous treadmill study, Jones tested experienced runners at six “per-kilometre” paces (5:44, 5:02, 4:28, 4:01, 3:39 and 3:21) while they ran on a treadmill that was either flat or inclined by various amounts. Setting the treadmill at a 1% incline made the effort equivalent to outdoor running only to those running 4:28 pace or faster. Let’s face it: Most of us are slower than that. You’re correct if you believe that treadmill runners don’t encounter the “cost” of moving through the air around them (because they don’t move; they stay in one place). But it simply doesn’t add up to anything significant unless you’re running 4:28 pace or faster.
What else can Kerrigan teach us about treadmill running? That the biomechanics, contrary to what many believe, are essentially the same as overground running. “We had to do a study on that to convince the U.S. National Institutes of Health to fund some of our other work,” she told Runner’s World. “People have a bias against treadmill running – that real runners don’t do it, or that it changes your leg movements. It’s all garbage. We found some minor changes, but they weren’t the ones people expected, and they don’t affect anyone’s running biomechanics.”
Kerrigan notes that she is often asked about holding onto a treadmill’s handles or side rails while running. Apparently some runners believe this is a good way to reduce ground reaction forces when they are injured. Kerrigan cautions against the approach. “You can really screw yourself up,” she says. “You might think you can push down with your arms to unweight your legs, but it’s almost impossible to get the timing right. Believe me, I’ve researched this.”
When it comes to her own treadmill running, Kerrigan favours simplicity. She selects the “manual” setting and doesn’t bother with any up-or-down inclines. “And I always choose the treadmill in my gym that I know overestimates my speed,” she says.