Often when arguing about the Leg Curl Machine being bad (eg. hurt your knees in many cases), people refer to the Glute-Ham-Raise as a way better (less harmful) alternative.
To me, the movements of the Machine Leg Curl and Glute-Ham-Raise look very alike. The arguments of Machine Leg Curls being bad for your knees can also partially applied to the Glute-Ham-Raise:
- knees are fixed -> sheer forces on the knees
- hip is not involved in the movement (stays straight in the case of the lying Leg Curl)
The only noticable difference to me personally is, that in the Glute-Ham-Raise you lift your body and in the Leg Curl you pull the arm of the machine towards your butt. So, again to me, they look very similar.
Where excactly is the difference between these two, and why are the Glute-Ham-Raises often told to be a way better option?