Two time-honored remedies for injured tendons seem to be falling on their faces in well-designed clinical trials.  he first, corticosteroid injections into the injured tendon, has been shown to provide only short-term relief, sometimes with poorer long-term results than doing nothing at all.

The second, resting the injured joint, is supposed to prevent matters from getting worse. But it may also fail to make them any better.
Rather, working the joint in a way that doesn’t aggravate the injury but strengthens supporting tissues and stimulates blood flow to the painful area may promote healing faster than “a tincture of time.”
Conlcusion:  “The stronger the shoulder muscles are when the tendinopathy calms down, the better shape the shoulder is in to take over movement without further injury,” Dr. Moffat said. “You don’t want the muscles to weaken, which is what happens when you rest and do nothing. That leaves you vulnerable to further injury.”