Guys I did leg press for the first time yesterday,the machine looks like this: Leg Press Machine I think it was the way I sit,but after doing a few sets of 10 reps,my lower back sort of hurts and is a bit stiff.I only did 20 kg(10 kg plate on each side) and it felt very easy to do.So I don't know why my lower back can hurt. Is it because this machine stresses the lower back a bit?What should I do now?