I had a pacemaker placed 5 weeks ago for sick sinus syndrome. I am back to normal activity, but I am worried that my sensor is pacing too slowly because the rate has not gone above 110 when I am exercising, and today I had symptoms post-exercise that I had pre-pacemaker (lightheaded and shaky legs). I do not understand how the sensor works and maybe the symptoms are normal for a 70 year old woman exercising too much. However, I thought maybe they could adjust my sensor so my hr will go to 120 or so. Anybody understand this stuff?