When you're short on time, it's a great idea to focus on your legs and butt, because that's where about 60 percent of your body's muscle is. This five-minute routine will work your lower half hard.

The key to this routine? Efficiency. For each of the five moves, go as hard as you can for 50 seconds, rest for 10, then go right into the next one. All you'll need is a pair of dumbbells (and a heavier set if you plan to make any of the moves more challenging).

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Sweat along in real time to the routine in the video below, and for instructions and a list of the moves, and how to make them harder, keep reading.

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The Moves:

1. Glute Bridge
How to make it harder: Raise one leg, and switch legs after 25 seconds. You can also raise your arms so they're pointing straight up or lift your toes off the ground.

2. Swing with Dumbbells
How to make it harder: Hold the heavier-weight dumbbells as you swing your arms forward.

3. Alternating Curtsy Lunge
How to make it harder: Hold the heavier-weight dumbbells as you lunge.

4. Low Sumo Squat
How to make it harder: Hold the heavier weight as you squat.

5. Iso-Explosive Squat

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