hi, thank you for providing the brief history of you. since you mentioned the stress test was normal and you are a regular exercises. it is really good to hear that you are really conscious about your health. I appreciate your indulgence. I think this pectoral pain can be a muscular one. I see most of the geriatric cases and look forward will all small and big things and never ignore even a single complain by them. why don t you look ahead to get the Pulmonary Function test as to check the lungs. usually due to inefficiecy of the lungs at times the pectorals function little up and down without a symptoms at times. doing regular breathing exercises like focussing on the costal breathing exercises should provide a good strength in the muscles or respiration as well as it will give exercise for the lungs with individual lobe as focussed. also it will be good if you meet a physical therapist he might help you to modify the regular exercises you are performing and also guide the new program which will be of help. getting a cardiac clearance from a cardiologist will put am additional benefit here. seeing your attitude towards the health and working out regularly I am highly impressed from you. with the grace of God I wish you a good health and a best future.