This exercise is the single leg hamstring curl. Like all hamstring curl exercise, you start with your feet up on top of the ball you’ll gonna first lift your hips up ground get your balance first, then center one leg and take the opposite leg off ball bring it up towards your chest.
Now keeping the hips where they are, bend the knee pulling in the heel in towards your hips and then back out. Its a much more challenging exercise than 2 leg hamstring curl, to make sure you go very slowly, no faster than 2 seconds in and 2 seconds back out. Inhale as you extend, exhale as you pull that ball in. you'll need to do 10 in one leg and then go over and do 10 reps on the other leg. You need 2-3 sets of this exercise. Once you finished all the necessary reps, you gonna move on to the next exercise.