Hi, I need help on the leg curls. I work them by doing 3 sets of 10. The problems im having are bad cramps. Whenever i do the second or third sets, i get really bad cramps in my hamstrings. It usually happens when i fully flex them. I don't know what to do. All the other things i do i have no problem with, like leg extensions, bench press, etc. I even try to stretch them for a couple minutes before doing them, but still same. It makes me hate working the hamstrings. Please help. Also, is it safe to work the quads and not the hams?