Short sprints of five to 15 seconds develop speed and power. Sprints of between 20 and 30 seconds improve fatigue resistance. Sprints longer than 30 seconds can improve your fitness, as they did for Agassi, but shorter sprints work your anaerobic system better. "The point is to get benefits you're not already getting from slow-steady cardio," says Snideman.
Credit: Mike Harrington / Getty Images
The 2014 Adventure Issue
From Iceland's Highway 1 to Utah's Canyonlands, an epic itinerary for modern explorers.
Plus: Building a Bigger Action Hero
ON NEWSSTANDS NOW
The Interpreters We Left Behind
The Rise of Cyclocross
Sign up to receive the Men’s Journal newsletter and special offers from MJ and its marketing partners.