Hold a dumbbell in each hand (or a kettlebell in both) and lift your left foot slightly off the ground. (You can also do this as a bodyweight exercise.)
Keep your back neutral and lean your entire torso forward while raising your left leg, which should stay in line with your body. The dumbbells will lower toward the ground.
With your back straight, return upright, coming to your starting position. This completes one rep. Maximise this move by keeping your left foot off the ground as you move through your reps.
Complete the same number of reps on the other side.