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
Powered By ZergNet
The Best Tools, Tech & Toys for 2015
Plus: The World's Most Efficient Workout
ON NEWSSTANDS NOW
Martin Short's Life Advice
Sign up to receive the Men’s Journal newsletter and special offers from MJ and its marketing partners.