Relative IntensityThe 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.