CHALLENGING YOURSELF during a workout doesn't have to be complicated. You don't need much time or equipment, just a plan and the determination to push yourself. Coach Milo Bryant has designed a tough but simple routine consisting of two matrices – a series of exercises targeting one muscle group, done circuit-style with no rest. You repeat these matrices as many times as possible in just five minutes. The first matrix focuses on squats, while the second is all about pushups. The goal is to complete as many rounds as possible within the time limit. Are you up for the challenge?