When you hear the word "cardio," what comes to mind? Maybe pounding the pavement or rides on an uncomfortable bike seat or any form of torture.

But your mindset will change after this countdown challenge from Men's Health Fitness Director B.J. Gaddour, C.S.C.S., because he's about to make cardio a heck of a lot more exciting. (Lose your gut without ever stepping on the treadmill again. Here are 1.)

The routine is simple, but super-effective. You'll grab a stopwatch, and time yourself doing only two bodyweight exercises -- €”the blast-off pushup and the lateral lunge with hop -- €”as a countdown. So you'll perform 20 reps of the blast-off pushup, and then immediately do 20 reps of the lateral lunge. Next you'll perform 18 reps of each. Then 16 reps. As you work your way down the ladder, you'll continue to decrease the number of reps by two until you make your way to zero.

Related: 10 Exercises That Burn More Calories Than Running

"You're cramming a ton of work into a short amount of time with minimal rest, which increases the intensity," says Gaddour, who demos the workout in the video. And he's not kidding. By the time you're finished, you'll have completed 110 fast-paced reps of each exercise or 220 reps total. A good time to shoot for is about 10 minutes, but you should write down your score and compete against yourself every week.

(Wondering how other guys reach their goals? These 6 Insanely Fit Guys Tell You One Thing They Do Each Day. It's practical AND inspirational.)

Find yourself slowing down? Gaddour offers up regressions -- €”removing the pushup and the hop from the exercises -- €”so you can keep barreling forward. You can also start with a lower number, like 12 or 14, and work your way up each week to improve your fitness.

More Men's Health:
-- 5-Pound Dumbbell Exercise That Absolutely Annihilates Calories
-- This Might Be The Craziest Mobility Exercise Ever
-- Best Sex Position For Your Aching Back
-- Why You Should Never Hold In Your Pee

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