MEASURING PHYSICAL ACTIVITY INTENSITY

Relative Intensity

The level of effort required by a person to do an activity. When using relative intensity, people pay attention to how physical activity affects their heart rate and breathing.

The talk test is a simple way to measure relative intensity. As a rule of thumb, if you’re doing moderate-intensity activity you can talk, but not sing, during the activity. If you’re doing vigorous-intensity activity, you will not be able to say more than a few words without pausing for a breath.

Absolute Intensity

The amount of energy used by the body per minute of activity. The table below lists examples of activities classified as moderate-intensity or vigorous-intensity based upon the amount of energy used by the body while doing the activity

TARGET HEART RATE AND ESTIMATED MAXIMUM HEART RATE

One way of monitoring physical activity intensity is to determine whether a person’s pulse or heart rate is within the target zone during physical activity.

For moderate-intensity physical activity, a person’s target heart rate should be 50 to 70% of his or her maximum heart rate. This maximum rate is based on the person’s age. An estimate of a person’s maximum age-related heart rate can be obtained by subtracting the person’s age from 220. For example, for a 50-year-old person, the estimated maximum age-related heart rate would be calculated as 220 – 50 years = 170 beats per minute (bpm).

The 50% and 70% levels would be:

• 50% level: 170 x 0.50 = 85 bpm, and
• 70% level: 170 x 0.70 = 119 bpm

Thus, moderate-intensity physical activity for a 50-year-old person will require that the heart rate remains between 85 and 119 bpm during physical activity.

For vigorous-intensity physical activity, a person’s target heart rate should be 70 to 85% of his or her maximum heart rate. To calculate this range, follow the same formula as used above, except change “50 and 70%” to “70 and 85%”. For example, for a 35-year-old person, the estimated maximum age-related heart rate would be calculated as 220 – 35 years = 185 beats per minute (bpm). The 70% and 85% levels would be:

• 70% level: 185 x 0.70 = 130 bpm, and
• 85% level: 185 x 0.85 = 157 bpm

Thus, vigorous-intensity physical activity for a 35-year-old person will require that the heart rate remains between 130 and 157 bpm during physical activity.