Generally speaking, if you move slowly, your muscles will grow faster, but the flexibility and reaction speed of your muscles will be negatively affected. Fast action is not as effective as slow action in increasing muscles, but it can make muscles more flexible and sensitive. Maybe you just entered the gym, and someone told you that if you want to grow muscles, you should first slow down the pace of fitness, learn the movements slowly and feel the stimulation of muscles first, instead of being proud of doing it quickly!