Hi; I'm new to this forum but I've been getting Dr. Mirkins Ezine for some time.  At 66 I have never been able to achieve any level of aerobic fitness in my life to now.  That is, I have never been able to jog let alone run.  Without going into my health, let me say it is excellent & at 6'0" I weigh 155lbs. & feel good physically & mentally.  My problem is that my heart rate comes up fast with minimal exertion but it also drops off fast when the exertion ceases.  No angina, not even a stitch, but even wearing a HRM to make sure I don't over speed the heart after a few weeks bicycling I become exhausted & require weeks to recover.  I have yet to find a Physician/Trainer with an answer/solution.  I can walk >3.5 mph with no problems & I live a normal life but I would (still) like to be able to improve my aerobic fitness or are my slow twitch so slow they can never achieve any fitness.

Thanks Claire; Not age related; always been this way.  Dr. Mirkin was kind enough to answer my question with some "exotic" suggestions which I have not pursued because I feel that even if I found an answer & I believe that to be unlikely there would be no "cure".  My RHR is in the 50s & returns after exercise to <100 quickly; all my numbers are good.  I believe I just don't have "jock genes" but I continue to do aerobic (bicycling) & anaerobic strength training because it make me feel so good.  I just have to control my desire to exceed 85% MHR for extended periods which overtires me for extended times. being type "A", that's hard.  Thanks again.  Bob