For example, practicing chest muscles with dumbbells generally requires three actions, which can be:

Push-ups, dumbbell bench presses, dumbbell birds

These three movements are divided into four groups, each group is 8 to 12, and each group is 20 to 30 push-ups.

8 to 12 means that when the weight of the dumbbell you choose reaches 8 to 12, it will run out, then take a rest for about a minute, and then do the next group, a ***4 group.

Push-ups are easier to do, so the number is between 20 and 30, and so are the four groups.

So the numbers from 8 to 12 are a group, because you have to rest for a minute after you finish.