There are a lot of different movements when it comes to working out. A Concentric movement is when the muscle you are working out is shortening, for example a biceps curl. Eccentric contractions are when the muscle lengthens in response to a greater opposing force. Isometric contractions are when you generate force with no change in the length of the muscle. When you are working out it is important to incorporate these movements into your workout. Eccentric movements are what is going to benefit you the most in building muscle due to the stress put on the muscle. I have recently started to incorporate eccentric movements by slowing bringing down each repetition instead of quickly and I felt the difference almost instantly. Instead of rushing through your workouts and sets, take your time and really feel the contraction of the muscle you are trying to work.