Weight training has the biggest effect on the skeletal muscles. When a person is engaged in weight training activities the skeletal muscles are forced to move beyond their comfort zone because of the added weight. As a result, muscle fibers develop micro-tears. These micro-tears when they regenerate through time increases the number of muscle fibers and the size of the fibers themselves.
The long term effect of weight training not only builds muscles but also improves the neuro-recruitment patterns of the muscles that are connected to the brain. When this happens movements become more fluid and activities are easily performed because of the developed connections of the muscle fibers to the brain.