Leg day doesn't have to consist of copious sets of squats at the gym. You can target this major muscle group and feel the burn in the pool, too. Whether you're using a kickboard or simply kicking on ...

Sweating and breathing in controlled spurts, like boxers, each kick-boxer extends a leg and lands a sweeping kick to the side of a heavy bag. Blam! Then they all dance backward on their toes, reset ...