2 to 1 Stability Ball Hamstring Curl

Lie on your back on an exercise mat with the stability ball in front of you.
Rest your feet and shins on the stability ball. Your arms should be extended out to your sides for support and balance.

Contract your abs, glutes and hamstrings, push through your heels and extend at the hips. Keep your core tight and don’t arch your lower back. Your ankles, knees, hips, shoulder should be roughly in a straight line.
From this position, flex your knees and curl your heels towards your butt. Keep your core tight, do not let your butt to drop down and don’t arch your lower back. If you find yourself getting a pump through your spinal erectors (lower back) then you’re likely substituting spinal extension for hip extension.

When you reach the top position, lift 1 leg off the ball.
Slowly lower back to the starting position with the other leg.

When you reach the starting position, bring your leg back on the ball.

On the next repetition, lift the other leg and switch the working legs on each repetition.
Repeat for the recommended number of repetitions.