Generally, when the heart beats more than 120 times per minute, it feels difficult to breathe and saliva becomes sticky, indicating that exercise should have reached its limit. During strenuous exercise, people's heart beats faster, muscles and capillaries dilate, and blood flows faster. At the same time, the rhythmic contraction of muscles will squeeze the venules, prompting blood to flow back to the heart quickly. After strenuous exercise, in order to keep the body temperature constant, blood vessels on the skin surface dilate, sweat pores open and sweat increases, which is beneficial to heat dissipation.
In exercise physiology, according to the relative intensity of muscle work, exercise can be divided into extreme intensity exercise, sub-extreme intensity exercise, high intensity exercise and moderate intensity exercise.
Extreme intensity exercise refers to the exercise that can last 10 to 30 seconds and work at maximum speed or strength, including periodic sports such as 100 meter sprint, 200m running, 50m swimming and short track speed skating, and non-periodic sports such as high jump, long jump, throwing, weightlifting and vault.
Sub-extreme intensity exercise refers to rapid and intense work that lasts for 30 seconds to 3 minutes, including periodic exercise such as 400 ~ 1500m running, 100 ~ 200m swimming, and non-periodic exercise such as floor exercise, martial arts, Sanda, wrestling and boxing.
High-intensity exercise means that the human body can work hard for 5 to 30 minutes, such as running 10000 meters. Moderate intensity exercise refers to periodic exercise lasting more than 30 minutes, including marathon running, road cycling, long-distance swimming and cross-country skiing.