Wednesday, June 18, 2008

Heart Rate Monitors

A while back Laura was given a heart rate monitor at work. "A new piece of technology? I gotta try it!" I ran with it for awhile and then used it in Bloomsday.
I find that once I get the settings tweaked just right it will pace me at my fastest sustainable speed.
The basic adjustments consist of a high alarm and low alarm. These tell you when your heart rate is outside the specified range. A good starting range is between 50% and 90% of your maximum heart rate. Below 50% and it doesn't really feel like exercise. Above 90% and it will be difficult to keep at it for long. Too much time above 90% produces dizziness and poor judgment. Keep this in mind when finding your MHR. Below 50% and it won't feel like real exercise.
There are two ways of finding your maximum heart rate (MHR).
-Run your brains out wearing your monitor and note the largest number you can attain (more accurate, doesn't require math)
-Subtract your age from 220 for men or 226 for women
Calculate the 50% and 90% heart rates. Here's where it gets interesting. Instead of just taking 50% & 90% of your MHR the Resting Heart Rate (RHR) is also used in the equation. RHR is best measured before you get out of bed in the morning.
BPM = Beats Per Minute
90% bpm = (MHR-RHR)*.9+RHR
50% bpm = (MHR-RHR)*.5+RHR
My Example:
I am 30.
My calculated max heart rate is 190 bpm. My run-my-brains-out max heart rate this morning was 192 bpm. (I actually measured it for this post!) My resting heart rate is about 70bpm.
90% bpm = (192-70)*.9+70 = 180bpm
50% bpm = (192-70)*.5+50 = 131bpm
In my months of playing around before I found these formulas online I decided that the highest heartrate I could sustain was 177 bpm and what I call the slacker alarm comes in at 133 bpm. Math people are too smart.
Tips and Tricks:
Until you get up a good sweat, the chest strap will have a hard time picking up your pulse. They sell special goo to help make the connection between the strap and your chest. I found that a dab of hand lotion on the sensor works just as well.
When exercising first thing in the morning, my heart behaves differently than the rest of the day. Normally it will increase slowly as the intensity of exercise increases. In the early mornings however, at the first sign of exercise it will quickly jump to around 120bpm and then very slowly creep toward my 90% rate.
Avoid exercising above 85% for 2 days in a row. Take it easy every other day and let your body rest and recover.

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