It depends on the purpose of exercise and the direction of muscle growth. If it is 1. Want to increase muscle mass and internal coordination, do three groups, each group 8- 12 times, all three groups can do 12 times to increase. 2. If you want to increase the internal coordination of muscles, do 3-5 groups, which are heavy, and each group does not exceed 5 times. If you can do it for 5 times, you will gain weight. 3. If you want to increase the muscle volume (dimension), don't exceed 3 groups, and each group should do at least 15 times to gain full weight. In addition, it is suggested that if it is fitness exercise, it can be done every day; If you are training to improve your sports performance and want to take part in the competition, it is recommended to carry out strength training every other day, so that the effect of strength gain is good.