Keep your core stable, and take a large step back with your right foot.
Plant your back foot and then lower your body until both knees are bent at a 90-degree angle. As you sink into the lunge, twist your torso to the left.
Bring your torso back to centre, and exhale as you straighten your legs and bring your feet back together.
Now step back on your left leg, twisting to the right.
Repeat for 40 seconds, 50 seconds, or one minute, depending on the round you're on.
For an optional challenge, hold a medicine ball or dumbbell at chest level while completing this exercise.