Here are are some ways to understand and measure the intensity of aerobic activity: relative intensity and absolute 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. In general, 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.
Moderate Intensity
- Walking briskly (3 miles per hour or faster, but not race-walking)
- Water aerobics
- Bicycling slower than 10 miles per hour
- Tennis (doubles)
- Ballroom dancing
- General gardening
Vigorous Intensity
- Race walking, jogging, or running
- Swimming laps
- Tennis (singles)
- Aerobic dancing
- Bicycling 10 miles per hour or faster
- Jumping rope
- Heavy gardening (continuous digging or hoeing)
- Hiking uphill or with a heavy backpack
https://www.cdc.gov/physicalactivity/basics/measuring/index.html