Everyone has different goals in the weight room. Some want to slim down, be more explosive/faster, or to put on size. You have to structure your training around your goals. I’m gonna tell you how to do that.
If you are trying to gain weight, you need to be lifting to gain weight. Lift heavy for low reps but focus on form. Do not lift light weights for 10-15 reps. That won’t do anything for your muscle mass. That is what people who want to slim down should do.
Like I just said, if you want to cut weight, you need to lift for it. High reps and high intensity. You should be taking very little rest in between sets to stay in a fat burning zone. Don’t take long gaps in between each set.
Now lets say you want to improve your speed, you need to be doing explosive lifts. Power cleans, squats, jump squats, and plyometrics are great for athletes trying to develop their speed. Anything explosive. It will activate your fast twitch muscle fibers and those are activated when you sprint.