Muscle Size vs Strength
Many bodybuilders get confused between training for size and training for strength. We all know that strength training involves low reps with a heavy weight as we try to increase our central nervous system (CNS) reaction to lifting a weight which takes time and patience.
The difference between strength training and size training can be described as your strength training is like upgrading the software (CNS) that recruits the muscles you need to lift a weight. Size training can be described as upgrading your hardware so that it is able to recruit more muscle fibers for each movement.
When training for size we want to upgrade our hardware which means our bones, our connective tissue and our muscles. Obviously there is a lot of overlap between these two concepts as you will increase the strength that you have when you are able to lift a weight with good form no matter how many reps you use.
The point is that most bodybuilders will at some time in their training get confused between training for size and training for strength. Lifting for size requires time under tension (TUT) which should be the primary concern when training specifically to increase the size of a muscle.
If you are unable to lift a weight because you are cheating, then the tension is reduced. Struggling to lift a weight through full range of motion (ROM) only reducers the TUT and will not increase size. Using more muscles to lift a weight will never increase size, you need to always be aware of TUT to increase the size of a muscle.
The prerequisites for building the size of any muscle is based on using strict form and doing a slow eccentric (lowering) movement for 3 seconds. It also requires you to squeeze at the peak contraction so that you are always aware of the muscle being targeted.
The last point to ensure size increase when training is to avoid locking out because the objective is to increase TUT. Training like this will automatically improve the results that you get if your objective is to increase the size of a muscle or muscle group.