HOW: Begin by sitting on the edge of a table or bed. Place a weight around the foot of the leg you are working. Lean back while pulling the knee of the leg without the weight to your chest. Engage your core by gentle flattening the back against the surface you are laying on. Raise the weighted leg up and then slowly lower it all of the way down in a controlled manner while keeping your core engaged. Repeat for the prescribed amount of reps.
FEEL: You should feel your hip flexor muscles working on the weighted leg.
COMPENSATION: Keep your back flat during the entirety of the motion, do not arch it. Slowly lower your leg down in a controlled manner, do not let the weight pull your leg down quickly.