I have to buy a HRM but until I can get around to doing it...which you never know...may be today, this is what I've figured out.
I am only aiming for 60-70% of my resting heart rate.
Resting heart rate is 14 beats per 10 sec
So would I do this...14 X .70 = 9
14+ 9= 23 ? And that would make 138 beats per min would be 70% of my resting HR?
I just worked the equation out that you gave me and its 135 , which is what I think I figured out. I think I am going to run to wal-mart later to see what they have on the selves.