Measuring Exercise Intensity
There are numerous benefits to beginning or continuing an exercise routine. Increased stamina and energy, decreased risks of cardiovascular disease, diabetes, obesity, and osteoporosis are just a few of the potential health benefits. At least 30 minutes of moderate intensity physical activity on most days of the week is recommended by the Center for Disease Control and Prevention (CDC) and the American College of Sports Medicine (ACSM). How do we determine and monitor the proper intensity for our desired health benefits?
Target Heart Rate
During aerobic exercise, your body utilizes more oxygen than at rest. As the exercise intensity increases and more oxygen is needed, your heart rate must increase to meet the demand. One method to estimate exercise intensity is by measuring exercise heart rate. The target heart rate zone for moderate intensity exercise is 65%-85% of maximum heart rate. Maximum heart rate varies depending on the age of the individual. By taking your pulse rate during exercise, you can determine if you are reaching your target zone. Electronic heart rate monitors are also available and can simply the process.
The ACSM recommends that each individual determines their target range based on current fitness levels. A de-conditioned individual may want to start at 50%-55%, while a well conditioned individual may occasionally exercise at 90% of maximum heart rate. Most adults who want to boost their fitness should focus on 65%-85%, for at least 30 minutes, most days of the week.
The Borg Scale
Although target heart rate is a great method for determining exercise intensity, it becomes less reliable as you age. Medications and chronic conditions, such as diabetes and cardiovascular diseases can alter the individual’s heart response to exercise. Others find it inconvenient to stop exercising to measure their pulse.
The Borg Scale relies on the individual’s perception of how hard they are exercising. The scale ranges from 6-20. A Borg Scale reading of 12-16 correlates with a target heart rate of 65%-85%.
The Borg Scale
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6
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20% effort - Very, very light (Rest)
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7
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30% effort
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8
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40% effort
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9
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50% effort - Very light - gentle walking
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10
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55% effort
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11
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60% effort - Fairly light
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12
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65% effort
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13
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70% effort - Moderately hard - steady pace
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14
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75% effort
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15
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80% effort - Hard
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16
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85% effort
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17
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90% effort - Very hard
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18
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95% effort
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19
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100% effort - Very, very hard
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20
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Exhaustion
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Before You Begin
Before beginning an exercise program you may want to consult your primary care physician for a medical evaluation. According to the ACSM, people who should consult a physician prior to beginning an exercise program are:
• Men aged 45 or older
• Women aged 55 or older
• People with 2 or more risk factors for coronary heart disease
• People with any major signs or symptoms of coronary heart disease
• People with disorders of the heart, lungs, or endocrine system (diabetes)
Measuring Your Pulse
1. Stop exercising.
2. Quickly (w/in 5 sec) find your pulse by placing 2 fingers on the thumb side of your wrist over the radial artery, or on the carotid artery in your neck.
3. Exert gentle pressure.
4. Use your watch to measure your beats per 10 seconds.
5. Multiply this number by 6.
6. Compare to your target rate.
7. Resume exercise.
Quick Tip: Determine what your target range should be for 10 seconds. This will help you avoid the multiplication stage. Divide your target heart rate for
1 minute by 6 to get your 10 second target range.
For example: Max heart rate: 190 Target heart rate: 124-161 = 21-27 beats per 10 sec
Calculating Maximum and Target Heart Rates
Age: 30
MHR: 220-age(30) = 190 beats per minute
THR (65%): 190 x .65 = 124 beats per minute
THR (85%): 190 x .85 = 162 beats per minute
THR (65%): 124/6 = 21 beats per 10 seconds
THR (85%): 162/6 = 27 beats per 10 seconds
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