Final answer:
Most people may benefit from aerobic activities when intensity reaches at least moderate intensity, where one can talk but not sing during activity.
Step-by-step explanation:
The U.S. Department of Health and Human Services recommends that aerobic activities reach at least moderate intensity to be beneficial. The 'Talk Test' is a simple method to gauge this: during moderate-intensity activities, you can talk but not sing, and during vigorous-intensity activities, you can say only a few words without stopping to breathe.
For adults, engaging in at least 150 minutes per week of moderate-intensity aerobic activity, or 75 minutes per week of vigorous-intensity activity, or a combination of both, is recommended for substantial health benefits. Moreover, muscle-strengthening activities of at least moderate intensity should be done on 2 or more days per week.