I have recently tried adding a cardio workout to my day. The trouble I am having is anything to strenuous causes a great deal of pressure in my skull. I try to keep going but it just becomes to much. When i stop the activity I am extremely tired. I could just fall asleep right then. I have noticed this over the last few years. Any kind of exertion leaves me feeling weak. Activities that I enjoy, like biking, leave me feeling very tired and sick but I could walk for miles and not feel tired. It does pass within a few minutes of resting but at my age it is embarassing and frightening. Does anyone know if this is due to my low BP? Any solutions to giving my heart a workout?