The age charts are crap and are built for the lowest common denominator. Your fitness level is what really counts. It's all based on your maximum heart rate and also the level (anaerobic threshold AT) where you go from aerobic to anaerobic. That the point where you shift to burning sugar exclusively for fuel. The simple math is to decuct your age from 180 but if you are fit you can't deduct as much. My AT at 52 should be around 130 but my at actually runs around 150-160.
I'm attaching a link for a chart that will help you help yourself. The second page discusses the various ways to determine your AT. It's alos important to understand that your AT can change 15-20 bpm from day-to-day depending on how much rest you've had, etc.
http://www.lifetimefitness.com/modul...ning_chart.pdf
And a few good articles:
Finding Your Maximum Aerobic Heart Rate : trifuel.com
Mark Allen on Heart Rate Training