Talk to any swimmer, and they'll insist that their workouts are harder than any other athlete's. They're probably right: Swimming laps for just 30 minutes can burn 400 calories. Plus, you're working just about every muscle in your body, says Jamie Grigas, a coach at EVF Performance in New York City. This workout was designed for a 25-yard pool (each lap is equal to 25 yards).
Warm Up: 300 yards freestyle, 100 yards kick (use a kickboard or perform a side kick), 200 yards freestyle, 50 yards kick.
Workout: Do 25 yards of kicking, followed by 50 yards of freestyle swimming, followed by 25 yards of kicking. Repeat 10 times, then swim an easy 50 yards to recover. Perform ten 25-yard pool lengths without breathing. Take as much time as you need to between 25-yard laps. (If you are not making the whole 25 yards, just try to make it longer than the previous one.)
Cool down: Perform a low-intensity backstroke for 100 yards.
