This move takes a typical lower-body exercise and adds a twist to engage your core. You'll be working your hips, glutes, and thighs, as well as your obliques (the muscles on the sides of your waist). Hold one dumbbell horizontally at chest level. Take a big step back with your left foot, then twist to the right. Return to center and push through your left heel to stand back up. Repeat the move on the other side. For beginners: You may need to practice the move without holding a dumbbell until you've mastered your form. Aim to do 10 lunges on each leg, rest, and repeat. Advanced: Work up to doing 20 lunges on each leg, rest, and repeat up to two more times. Tips: Move slowly and with control, especially if you're a beginner. Inhale as you step back, and exhale as you twist and return to standing. Keep your core tight and your shoulders down throughout the move. Make sure your back knee doesn't touch the ground as you lunge (it should hover right above the floor).