Stars may not grow muscles when running, but usually they choose to control their running speed and duration to avoid excessive muscle growth. This is because long-term high-intensity training (such as long-distance running) can increase muscle mass, and for some stars, they want to keep elegant figure and figure and avoid too muscular body lines. In addition, some stars may take other forms of aerobic exercise and strength exercise to achieve their desired body shape and health goals. These sports include swimming, yoga, pilates and so on. This kind of exercise pays more attention to physical fitness than muscle development. In addition, some stars will control their diet and reduce their muscle mass by controlling protein and calorie intake. Therefore, stars may not grow muscles when running, but they may take a series of measures to control the growth of muscles and keep their bodies graceful.