Every time I went to the gym, I was exhausted, but the last two groups did their best to finish with almost no sense of tearing and pain. Why?

If you want to exercise explosive power, it is absolute strength. Can't do it according to the number of groups. You need to do heavy weight-bearing exercises, one or two or three at a time. Of course, you need someone to help you That weight is basically close to your limit. For safety reasons.

In fact, sometimes a small weight can further increase your explosive power. There is a saying that muscles and nerves can be adjusted with a small weight, so that when exerting force, they can exert force together, instead of some muscles not exerting force, and even some muscles hinder beneficial exertion.