People who don't exercise will make rapid progress at the beginning of training. Most people have really made great progress at this level. The principle is that a certain training mode can stimulate muscles and nervous system for 5~6 weeks. But after this period of time, the body adapted to the stimulus, and the growth of strength naturally slowed down.

Normal fitness experts will change the training mode every month to keep the body under fresh stimulation and keep the muscles as long as the training period.