I am a 27 year old female and have 2 children. I have gained a significant amount of weight since my second child, mostly in my mid-section, which I have been told can lead to heart problems. I have recently been experiencing numbness on the entire back of my left arm any time I exert myself by walking (slow or fast) more than an hour or so. It doesn't tingle, but feels swollen and numb. My sister suggested it has something to do with my circulation. I am not very active at all, but would like to change this by walking and eventually jogging, but I am scared about the numbness being a symptom of something more serious.