When you work out your muscles, they get stronger. When a person keeps practicing using the Force everyday, will they get stronger in its use?
As depicted in the movies, learning to use the Force is more like learning a martial art than simply building up a muscle. Physical conditioning is clearly part of the training, as we saw Luke running through the jungle on Dagobah with Yoda on his back exhorting him. But it's also a mental discipline that must be mastered through expert instruction and practice.