Girls should not worry too much that running will thicken the long muscles of calves, because the hypertrophy of muscle fibers must be affected by the hormone testosterone, and the amount of this hormone in girls is only one-third of that of boys. It's not that easy for boys to practice muscles, let alone girls. If you have already practiced, don't worry too much, because there is a theory in kinematics called "use in and waste out", which means that muscle fibers will shrink if you don't exercise for a while. . T_t's own muscles have recovered to the pre-training level because they haven't trained for more than a year. . .