The beating of the heart causes blood circulation. For the same person, the faster the heart rate, the more blood enters the circulation per unit time. The red blood cells in the blood transport oxygen,Generally speaking, the oxygen obtained by a person through blood circulation per unit time The more, the better his physical fitness and performance. Therefore, in order to improve athletes' competitive level in sports competitions, they should strengthen their training in high altitude areas, because in high altitude areas, each unit volume of blood in the human body contains the number of red blood cells is higher than in low altitude areas.
Which of the following items must be assumed in the argument of the subject?
The altitude has no effect on the athlete's heart rate