Add some dumbbells to your fitness routine and build some metabolism-boosting muscle while toning your entire body. We leave no muscle untouched with this workout, so grab a set of dumbbells between two and 10 kilos. Better yet, grab two sets — so you can challenge yourself on a few of the moves with heavier weights. The more often and consistently you lift, the more you will be able to lift! Directions: Warm up with five minutes of light cardio, then repeat each three-exercise circuit three times. Start with 10 reps of each exercise, building up to 15 reps of each move as you get stronger.