Hamstring curl progression on stability ball

The first hamstring curl with a stability ball that I did was shortly after completing knee rehab.  My personal trainer knew I was ready for more and that I had a stability ball at home already.  This video goes thru a progression from 2-legged to single.

Hand placement can be used to change difficulty starting with the hands out to the side, then going to elbows only bracing, finally arms up for the hardest.

Stability Ball Hamstring Curl Progression:

1. (Easiest). 2 Legged
2. 2 Legs on Up (concentric), 1 Leg on Down (eccentric); no alternating
3. 2 Legs on Up (concentric), 1 Leg on Down (eccentric); alternating
4. (Hardest). Single Leg