To find your MHR, either take a graded treadmill stress test to exhaustion or, with your doctor's blessing, run an all-out two-mile time trial on the track and then take your pulse.
To determine your RHR, count your pulse for a full minute the first thing in the morning (while lying in bed) for several days in a row and average the results.
Then, use the following formula to establish your different levels of workout effort. Subtract half your age from 205, then subtract your RHR from that number. Multiply the result by 0.70, 0.85, and 0.90--the percentages of effort for three different types of workout.
Finally, add your RHR back to these three figures. What you'll come up with is the number of heartbeats per minute you should maintain while running at 70 percent, 85 percent, and 90 percent of maximum.
To apply these numbers, follow a training pattern that separates hard days of 85 to 90 percent effort with easy days of 70 percent and under.
For example, run easy on Mondays, Wednesdays, and Fridays at sub-70 percent effort. On Tuesdays, do 2 to 3 miles of hard intervals at 90 percent effort with easy recoveries at sub-70 percent. Do a fartlek workout on Thursday, setting your monitor between 70 and 85 percent effort and running fast until it beeps at 70 percent. A tempo run on Saturday should include 15 to 20 minutes at 80 to 85 percent effort, and your long run on Sunday should be steady at 65 to 75 percent effort.
Learn more ways to use your heart rate monitor to improve fitness.