Sweat spot

This article appears in the August 8 issue of ESPN The Magazine.

THE JOCK: Mark Weir, mountain biker

THE WORKOUT: Slack-line walking

THE BENEFIT: Improved balance and body control

When Mark Weir first strung a slack line across the backyard of his Marin County, Calif., home, he was more concerned with being mocked by friends than being clocked by a fall.
"Now it's like, who cares?" says the 36-year-old mountain biker. "I'm an idiot anyway." Weir first got his circus on two years ago, when he was stuck in the woods with nothing to pass the time until his rescue except the towline tied between his immobile jeep and a nearby tree. Since then he's spent at least an hour, three or four times a week, walking his backyard line. When he does, he holds a set of handlebars to simulate a riding position. Balance on the line originates from his core, and increased core strength means more control when he's hunched over his wheels. At first the biggest challenge was just staying put; it was two weeks before he could stand without having to hold onto a tree. These days, it's not if he can stay vertical, but how long. "I like to see how many seconds I can stay on," Weir says. "It's like rodeo, except the 2,000-pound bull is a one-pound rope."