Get ready to sweat and push your body to its limits with this countdown challenge from Todd Durkin, C.S.C.S., owner of Fitness Quest 10 and author of The IMPACT! Body Plan. You'll perform two combination exercises -- two or more moves blended together -- at high-speed, working a ton of muscle mass and incinerating a bunch of calories in the process. (Turn up your muscle gains outside the gym. These 18 Ways to Build Muscle All Day will help you shed fat, sculpt muscle, and accelerate recovery.)
Here's how it works: Grab a pair of 25-pound dumbbells. Perform 5 reps of the squat to curl and press, then immediately do 5 reps of the pushup and row. That's 1 round. During the next round, do 4 reps of the squat to curl and press, followed by 4 reps of the pushup and row. Continue to decrease the number of reps each round until you perform only one rep of each combo move.
Want to give it a shot? Watch the video above to see how to perform the challenge with perfect form. Durkin completed the countdown in one minute and 47 seconds. However, the best time belongs to Fitness Quest 10 personal trainer Mitch Ryan, who finished the challenge in one minute and 4 seconds. (Boost your gains by downsizing your workout with The One Dumbbell Workout.)