With me, it was just that I was increasing in strength fast and was putting myself under a lot of stress. I think also that you physicologoy push yourself harder cos you want to get the max benefit from the cycle. I was pushing the leg press hard and so buggered my knee a little also I have 3 prolapse disks and a warped spinal column so I am susceptible to back injuries moreso that others. :shock:
I would say loads of stretching and warmups and good form is the key
Will pm a mod to answer your questions cos I wanna know myself
cheers