When we work out, you can either use momentum....or you can utilize muscle activation. When you go fast, as many do in the gym thinking they are really doing something, you are more prone to injury. Think about it! You have a 60lb weight in your hand and you are pulling it up and down towards your shoulders to work the bicep. Your mission is to get that weight up as fast as you can and down right? WRONG..... If you want to tear your bicep, certainly, but if your goal is developing a beautiful muscle, your goal should be on speed (tempo) and form.
You may hear 4/4, which is up, up, up and up....then, down, down, down and down, not just up and down. When you concentrate on tempo, usually 2/2, 3/1, 1/3.....you get a much better workout. Happiness to you on this beautiful Monday.