Just when we think we've heard it all about the beloved kettlebell—Whittles your belly! Boosts balance! Sculpts from calves to tris!—science hands us another reason to reach for the iron orb. In a new study, women who followed a specific 20-minute kettlebell interval workout three times a week for a month amped their VO₂ max (a measure of aerobic fitness) by 6 percent (sounds minor, but it's actually pretty impressive). Those who did a circuit routine of pushups, situps, and two-minute sprints saw no such improvement. So: This strength-training tool is also a cardio dynamo.
(Looking to gain muscle and a sexy, toned body? In her book, Lift to Get Lean, Holly Perkins, certified strength and conditioning specialist, explains how you can score a slim figure in four weeks.)
"The kettlebell's design makes it easy to swing and move quickly between exercises," says certified strength and conditioning specialist Tony Gentilcore, who created this cardio-rich sesh. "That keeps the intensity high and allows for shorter rest breaks, which elevates your heart rate for a cardio effect that improves aerobic conditioning." Add the fat-torching, body-shaping perks you typically get with the bell and bam!—fast results.
The workout: Do the moves in order without stopping in between. At the end, rest 60 to 90 seconds, then repeat the circuit at least twice more. Complete this routine two or three times a week.
Check out the pinable graphic below, and then scroll down the page for a play-by-play of each move.