"You can train for a race [by] doing stairs, but you can’t train for stairs just running," says Rekhviashvili. "Stairs are a whole different ballgame."
"Running can help a little if you do a lot of uphill, or if you’re sprinting. The key is you're driving the knee a lot higher and extending your step and a lot more power. And that's what doing stairs is -- using more power to drive through."
Another benefit? You will tear up flat courses like a total beast.
"If you run a mile on a hill long enough, or run up flights of stairs, your mile on a flat will be a lot faster. Flat feels like nothing after incline."
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Liz Newman is a freelance writer for Thrillist and was actually trained by Nik the same year she ran two long-distance races. She still refuses to unveil the true identity of "Annoying Fit Person." Follow her on Twitter and Instagram at @lizn813.