I am 47 y/o male in reasonably good health. I work out at the gym 4-5 times per week, treadmill, weight machines. I have a very active job, as I do not sit at a desk all day, but work on HVAC equipment. I have begun experiencing a prickly, tingling sensation in my feet, both top and bottom; not always on both feet or same side, intermittent in nature. Not diabetic, no known heart problems. Had a cardiac workup year and a half ago which was normal in all respects. Eat a healthful diet, keeping saturated fats at a minimum. Could this be caused by back strain, lumbar disc problems, or something more serious like circulatory problems?