I've been a casual bike commuter for a few months now
but would like to start getting the best exercize from my ride.
I recently bought a HRM and use it to stay between 70% and
85% of my max heart rate (measured by 220 - age).
Can you tell me if there's a 'rule of thumb' about measuring
recovery rates? I think my HRM will do this but I have no
idea what it would mean to return to a given rate in a given
time. How do you know if your recovery time is good or bad?