My title pretty much says it all. In my current routine, i'm supposed to do leg curls on Tuesday (leg day) and hyperextensions (back day) on Thursday. However, my gym's leg curl machine is broken. In this case, would it be fine to just do straight leg deadlifts on Thursday and remove these two exercises? Also, what is the difference between straight leg and stiff leg and would you recommend keeping your back straight or let it bend (on purpose)?