Bored of your usual interval workout? Keep things fresh, literally, by hopping in the pool. Known to help reduce belly fat [1], intervals can be practiced beyond the bike or treadmill. Although this swim workout has a little bit of everything, the middle portion includes a few short bursts where you play with stroke and speed. This workout is great for days in between lengthy endurance runs. And don't skip the always-important long warmdown [2] to finish the workout.

Interval Workout: Swimming

Warmup: 350 yards
50 yards freestyle — easy
100 yards backstroke
200 yards freestyle

Endurance: 600 yards
2 x 100 yards pull* freestyle
2 x 100 yards kick** freestyle
2 x 100 yards freestyle

Intervals: 500 yards
4 x 50 (1 of each stroke) — strong (rest: 30 seconds)***
2 x 25 freestyle — sprint (rest: 15)
—Rest 1 minute, repeat the set—

Warmdown: 400 yards
4 x 100 yards — 50 yards freestyle, 50 yards backstroke (rest: as needed)

Total: 1,850 yards.

*Pull: Hold a buoy [3] with your legs and use only your arms to swim
**Kick: Use a kickboard and use just your legs to power yourself across the pool
***Rest the listed amount between reps/laps