"Moderate activity" is any activity that allows you to talk while doing it while a "vigorous activity" is any activity that <u><em>doesn't allow you to talk while performing it.</em></u>
An example of a moderate activity is <em>"walking."</em> You may have noticed that most people with friends talk while they walk. This is because their <em>heart rate</em> <u>is not that fast</u>, and it doesn't affect much of their breathing.
An example of a vigorous activity is <em>"running."</em>People who run don't have the energy to talk, or if they ever do, <em>they pause for a bit</em>. This is because their <em>heart rate</em><u> is very fast</u>, and this affects their breathing. Thus, it is not common to see people running side-by-side while talking.
