Natural Leg Curls

Starting from a kneeling position and with the assistance of a partner, keep your hips flat and start lowering your torso to the floor as slowly as possible. You may support yourself with the tips of your fingers in the beginning. When you go back pull your hamstring to go back to kneeling position.

Half Glute Ham Raises

Start this variation as a normal leg curl and with a partner securing the ankles , tilt you hips forward as far as you can while maintaining a straight body and keep a FLAT back. Lower the forehead to the ground and return back to the straight body tilted position. Do not return to the upright position till you have completed all the desired repetitions. You may also hold a plate or any weight to make this variation more challenging.

Single Leg

Use just one leg instead and the switch to other leg. afterward, you may hold a weight to make the already-challenging variation more challenging. All the stress will be diverted to your hamstring instead of the lower back.

Glute Ham Raises

Use a plyo box or GHR unit or a bench for this variation. Your feet should be secured firmly and your hips should be on the edge of whatever support you have chosen. Drop your chest forward untill you are hanging vertically upside down and while utilizing the lower back lift the torso up to horizontal and then sraise yourself to vertical by
contracting your hamstrings till you end up sitting completely upright. Pause then repeat.

You may use speed to make this variation easier. When you progress reduce the mementum and try straighten your body during the whole movement.