Hello, Your problem may have various different causes. Some of them contribute to your symptoms without each of them being the main cause. Fatigue is a symptom of PMR, so having this symptom may just mean that your PMR has got worse. Taking prednisone is another factor that may come into play as corticosteroids may predispose to muscle weakening. Weak muscles may become fatigued sooner. Heart failure is another disorder that may present with fatigue, particularly after strenuous or prolonged activities. Finally respiratory tract disorders like emphysema reduce the availability of oxygen that your body can use when involved into physical activities, thus making your muscles less capable to maintain anything more than a minor level of activity for long. There are treatments for heart failure and respiratory tract disorders. Muscle wasting due to the corticosteroids is not very easy to deal with but a daily exercise routine may help. Hope I have answered your query. Let me know if I can assist you further. Regards, Dr. Panagiotis Zografakis, Internal Medicine Specialist