## Heart Rate During Exercise

When you begin to exercise, your heart rate increases rapidly in proportion to your exercise intensity. When the rate of work (intensity) is accurately controlled and measured (for example, on a cycle ergometer), the oxygen uptake can be predicted. Thus, expressing the rate of work or exercise intensity in terms of oxygen uptake is not only accurate but is appropriate for comparing either different people or an individual under different circumstances.

Your heart rate increases directly as you increase your exercise intensity, until you are near the point of exhaustion as in Olympic cross-country skiing. As that point is approached, your heart rate begins to level off. This indicates that you are approaching your maximum value. The maximum heart is the highest heart rate value you achieve in an all-out effort to the point of exhaustion. This is a highly reliable value that remains constant from day to day and changes only slightly from year to year.

Estimates of maximum heart rate can be made based on your age because maximum heart rate shows a slight but steady decrease of about 1 beat per year beginning at 10 to 15 years of age. Subtracting your age from 220 provides an approximation of your average maximum heart rate. However, this is only an estimation - individual values vary considerably from this average value. To illustrate, for a 40 year old, maxi-mum heart rate would be estimated at 180 beats per minute (HR max = 220 - 40). For all 40 year olds, however, 68% will have actual maximum heart rate values between 168 and 192 beats per minute (mean ± 1 standard deviation), and 95% will fall between 156 and 204 beats per minute (mean ± 2 standard deviations). Knowing your maximal heart rate values has application in estimating your target heart rate. The target heart rate (THR) helps you to train at the appropriate intensity to maximize performance benefits of your training efforts.

To determine your target-zone heart rate, you must first estimate your maximal heart rate. It can be measured by:

220 - Age(in years) = ___________ (MHR)

Now you can estimate your target-zone heart rate:

Lower level = 0.60 x MHR = _____________
This is your target zone for 60% of your maximum heart rate

Upper level = 0.85 x MHR = _____________
This is your target zone for 85% of your maximum heart rate

 One Olympic x-c skier reported that he has recorded his resting heart rate at 29 beats per minute!

Determine your resting heart rate by lying down for one minute while listening to calming music, and then check your pulse. Count the number of heart beatws that occur in 10 seconds. Multiply that number by 6.

Example: 12 beats in 10 sec. = 12 x 6 = 72

Complete the target heart rate worksheet.

 Start with 220 and subtract your age Example: 220 - 40 For you: Equals maximum times the heart should beat per minute. Subtract resting heart rate. 180 - 72 Multiply by 60% 180 X 0.60 Add resting heart rate 64.8 + 72 Equals target heart rate (THR) Divide by 6 (Note: 6 increments of 10 seconds per minute) 137 beats per minute 137 ÷ 6 = 23 23 beats for 10 seconds Your THR for 10 seconds

Do a 12-minute walk/run at 4-minute intervals. At these itnervals, find your heart rate and check to see if you are in your range that you calculated. * Remember, count the number of heart beats that occur in 10 seconds.

© April, 1998, Montana State University-Bozeman