The No-Weights Workout: Push-Ups
Push-ups ignite more than 100 muscles, but few guys do them with proper form. Be sure to keep your back and neck straight, and glutes and core engaged. Always lower yourself slowly, bringing your chest almost to the floor before pushing up.
Make it Hard
Place one hand on a basketball and roll from hand to hand on each rep.
Try a one-handed push-up by putting one hand behind your back and spreading your legs wide.