Muscle growth is very difficult. If you want to increase muscle strength and girth through exercise, you must meet certain exercise standards. These standards are mainly reflected in training intensity, training volume and training frequency. In terms of training intensity, it is possible to stimulate muscle growth when an action reaches the physical strength limit within 15 repetitions. That is to say, when you jump rope to the fifth time 15, and your physical strength has reached the fatigue limit and you are unable to repeat the sixth time 16, this exercise is likely to increase your muscles.