Exercise intensity refers to the strength and physical tension used to complete exercise in unit time. The main factors affecting the intensity of exercise are the speed and negative weight in the process of exercise. For example, junior high school students can run 100 meters and jog 1 minute, and their heart rate can immediately reach 180 beats/minute, and the heart rate is generally around 130 beats/minute. Obviously, the former is strong and the latter is weak. In sports activities, the events with high intensity include running, jumping and climbing, while the intensity of walking, climbing and throwing is relatively small. 2 Exercise time

Exercise time refers to the total time of a physical education class exercise or the interval of each exercise. Under the condition of ensuring a certain reasonable intensity and density, the length of exercise time is directly related to the size of exercise load. If students are in high-intensity exercise for a long time in a class, then their exercise load is too great. 3 practice density

Exercise density refers to the number of repeated exercises per unit time, which reflects the relationship between time and quantity in exercise load. Whether the exercise density is appropriate or not has a great influence on students' exercise load, which is generally proportional to the exercise load. 4. Teachers' teaching contents, teaching methods and organizational measures

Whether the teacher arranges physical education class's content properly, whether the teaching method is appropriate, whether the organization measures are appropriate, and whether the explanation and demonstration are correct, vivid and standardized will greatly affect the exercise load. For example, too few groups in teaching lead to long waiting time for students, which makes the exercise load too small; For example, the interval time of practice is large or small, which leads to excessive exercise load. 5 students' individual differences

The individual difference of students refers to the individual difference of students' physical function level. In physical education class, the same exercise often produces different effects for different students. For example, if you run 60 meters quickly, some students' heart rate will reach more than 180 beats/min, while others will only 170 beats/min.