Speed is a game breaker in football. Todd Durkin, C.S.C.S., the owner of Fitness Quest 10 in San Diego and trainer for Saints running back Darren Sproles and a cadre of other elite NFL players, created the Terrible Treadmill 10 challenge to forge quickness.

"Running uphill at a high incline forces you to drive your legs and knees up, extend your hips back, and explode off the balls of your feet -- all skills that increase your ability to propel your body forward in an all-out sprint on flat ground," says Durkin. (Turn up your muscle gains outside the gym. These 18 Ways to Build Muscle All Day will help you shed fat, sculpt muscle, and accelerate recovery.

The Sproles Standard: 13.5 mph

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Here's how it works: Set the treadmill at a 10 percent incline. Sprint as fast as you can for 30 seconds, and then rest for 30 seconds. That's 1 round; do 10 rounds total. Your goal is to maintain your fastest speed for all 10 sprints. (Be careful: Hold the rails when getting on and off the treadmill.)

(Beat your workout plateaus with this 5-move The Total-Body Muscle Assault.)