What I have recently learned may be useful to some PMR victims who experience shortness of breath on exertion.
I am an almost 82 yr male who has maintained a high fitness level until PMR - diagnosed last August but almost certainly affected as early as the previous August. A typical beginning medrol dosage of 16mg/day brought immediate miraculous relief. My aerobic capability returned completely.
As I began to reduce dosage, I noticed in retrospect a reduction in aerobic "fitness" as some stiffness of my back also increased. Because the stiffness increased but was still tolerable I paid inadequate attention to the aerobic change. As I reduced dosage further (last low dosage was 3.5mg/day) there was drastic shortness of breath with little exertion. It was not acceptable.
I did considerable online research and found a small number of medical papers noting an association of interstitial lung disorder with PMR. I increased my medrol to 12mg/day and noticed a change in aerobic capability almost as dramatic as the initial (miraculous) relief of PMR on first starting medrol.
Had I not increased medrol I am firmly convinced that my lungs would have suffered irreversible damage.
I believe that anyone suffering from PMR should pay close attention to aerobic capability as they try to wean from medrol. While lower doses of medrol may lower the risks associated corticosteroids they may endanger the lungs. For those noticing aerobic insufficiency I suggest serious consultation with their physicians. But it may be necessary to make your own decisions. In my case two rheumatologists told me there was no relation of shortness of breath to PMR or medrol.
PS, I walked today at a rate of 12min40sec to the mile with no distress whatsoever. And I have been down to 10.5mg/day for 10 days.