A lot of training guides I consult for my running and cycling training talk of heart-rate "zones." I have been looking at the wide range of heart-rate monitors and wondering if you could suggest one that's reasonably priced and good for running and cycling? Michael Providence, Rhode Island

I'm dumbfounded by all the choices with regard to heart rate monitors. Should I stick with the well-respected Polar or try other brands? Tracy Los Angeles, California

Calling all fitness Luddites and low-tech aerobic warriors—it's time to change your ways. Let us unlock the mysteries of heart-rate training and help you maximize your workouts.

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