No confusion there right? Not surprising since there are multiple variables involved. Not to mention the sticker shocks. Run 50 miles a week in $150 shoes and every two and a half months your gear-and-apparel budget is getting some serious drainage.
"Here are some fun facts," says Jay Dicharry, author of Runner's Anatomy: Unlocking Your Athletic Potential for Health, Speed, and Injury Prevention. Dicharry is a physical therapist and biomechanics expert, and is a key advisor to Ironman champion Linsey Corbin. Reports Dicharry, "One well designed research study shows that shoes lose about 40 percent of their cushioning by the time they've reached 200 miles. So the old adage to 'throw them out at 500 miles' isn't really an an all-or-nothing thing. Shoes break down with use, starting from the first step. And research shows that the body adapts slightly to adjust to these changes."
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It's the last part that spurs Dicharry to let us know what can be done to take more control of the situation. Including the likes of Corbin, Dicharry essentially conducts research experiments with his clients and their biomechanics, studying the patterns of movement in fine detail to look not just for injury-inducing flaws that can be corrected, but for real-time, intricate adaptations that can help him better see opportunities for increased power flow.
"In general, people make small adjustments in their motion to minimize the mechanical work they are doing. It's kind of a self-preservation strategy to maintain efficiency."
Dicharry adds that sometimes these minute changes in range of motion are harmless. They allow a triathlete or runner to keep on trucking just fine in lifeless, broken down shoes.
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"I had a previous runner that had excellent biomechanics," Dicharry says. "He wasn't really dependent on the shoe for anything, and routinely got 1200 to 1400 miles out of a single pair of shoes."
Right: Dicharry is talking about those runners like Dean Karnazes, who apparently have such perfectly-spun mechanics that they can run across the country and back with nothing more damaging than blisters.
As for the rest of us, one of the ways we know a shoe has lost it's cushioning is that nagging injuries start lighting up in the way of a pinball machine.
"There runners are more sensitive to the small changes in gait—either due to their structural needs as a runner or their biomechanics—and begin to feel symptoms brought on like clockwork every time they hit 'X'-number of miles."
What can we do? Dicharry encourages the latter-type of athlete (most of us, as suggested by injury data) be more like Karnazes and other seamless runners.
"One strategy to prolong the life of your shoes is to improve you," he says. "Make yourself less dependent on the shoes by relying more on your inherent foot stability." This is done, Dicharry says, by strengthening your feet. "Shoes do matter, and make a difference, but 100 percent co-dependent relationships are never a good thing."
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