Eccentric loading is the new buzz word in tendinosis (or tendinitis as it was called). Basically it involves loading the problem tendon with a stretch not a shortening movement. With the achillies you hang the heel of the bad leg off the edge of the step, the other foot is on the step. take weight onto the bad leg and lower through your calf stretching the achillies. transfer your weight onto the good leg and lift/push yourself back up onto the step ( circular motion between both legs). The theory in it's basic form is that tendinosis has swelling between the fibers of a tendon eccentrically (stretching) loading it elongates the muscle thus squeezing out the fluid (very bad analogy but you get it!)
You need to start with these reps of 15 3 times a day without fail for 2-3 weeks then return to add basic heel lifts, squats and your normal training programme. See how it goes you should not be in agony but a little discomfort is ok.
If in doubt go and see a physio!! - let me know how it goes