Im on 20 pounds for straight leg lifts and partial leg extensions (im not sure what a curl is).
Physio tells me you can safetly add 1 kilo a week (thats 2.2 pounds to me and you) - but that you should always feel what youre on is 'easy' before going up in weight. Youve gotta be able to perform the exercise slowly, with full control, and no cheating

, before you increase the weight.
At one point in life i was up on 36 pounds for leg extensions, but i was literally getting my leg swinging and then swinging to maximum extension, and letting down by dropping - no control at all - thats how NOT to use weights
