Hold a dumbbell in each hand, or use one dumbbell and hold one end of the dumbbell in each hand. Plant both feet on the floor shoulder-width apart. This is your starting position.
Bend your left knee slightly. Without changing the angle of your left knee, hinge forwards from your hips until your torso is parallel to the floor, extending your right leg behind you. At the same time, extend your arms towards the floor. Ensure that you keep your hips level, maintain a proud chest. You
should feel tension in your left hamstring (back of your leg).
Push through your left heel and, using your glute and hamstrings, extend your hips to return to the starting position.
Continue reps on the same side for half the specified time (about 22.5 seconds) before completing the remaining reps on the other side for the remaining 22.5 seconds (45 seconds of movement total.) Then rest for 15 seconds.