you want to gain muscle mass as quickly as possible you have
to try to increase the weights you use during exercise
repeatedly in small increments while sticking to proper
technique while lifting.
Only when the muscle is exposed to progressively
larger loads will it adapt and react by growing.
principle is called the "overload-principle" and is not
only the basis but the only way of building muscle mass.
Let's say you are barely able, using maximum exertion,
to complete 7 repetitions without assistance, using 90kg
(200 lb) while doing benchpresses. If you want to continue
to stimulate your chest muscles to grow you have to break
this limit. During your next set or your next training
session you have to either perform more than 7 repetitions
or increase the weight used to 92 or even 95 kg (205 or
the only way to assure that your muscles receive sufficient
growth stimulus and therefore increase in size. If you are not
sure whether you are actually performing an exercise
correctly, please ask an experienced trainer or bodybuilder to
show you how. Let common sense as well as your feelings guide
you as to the speed of the individual repetitions.