Because when alternating, the muscles you exercise are different. For example, push-ups mainly exercise pectoralis major and triceps brachii, and sit-ups mainly exercise rectus abdominis. When doing one of the exercises, the muscles in other parts can be rested and partially recovered, which improves the exercise efficiency and keeps the exercise intensity at a high level. However, a single part repeatedly moves, and it takes longer to complete the same total load, which reduces the efficiency and interrupts the movement process.

When alternating, we should arrange the order of each project reasonably, such as training large muscle groups first and then training small muscle groups; Upper limbs, lower limbs, waist and abdomen take turns; Dynamic action and static action alternate, and so on.

It is good enough to practice the same project 3-4 times a week, and give them some time to recover (1-2 times should be the ultimate or sub-ultimate strength to achieve the excessive recovery effect mentioned in the training).