Full-cycle monitoring of exercise physiology: Scientific responses from pre-competition condition and peak performance to "rejuvenation".

During exercise, the body's functional state changes according to strict biological laws, typically going through five stages: pre-competition state, working state, steady state, fatigue, and recovery. Understanding the characteristics of these stages is of practical significance for preventing exercise-related risks and improving the effectiveness of exercise for weight loss.

The functional state of the body before starting exercise is called the "pre-competition state," also known as the start-up state. This is a conditioned reflex response; some people experience lethargy, while others become overly nervous. Sufficient warm-up activities can regulate the excitability of the cerebral cortex, thus adjusting the pre-competition state and preparing the body psychologically and physiologically for the upcoming load.

The next stage is "entering working mode," and the most important event in this stage is the "hitting the wall" (or "reaching the limit"). The hitting the wall occurs because, at the beginning of exercise, the mobilization rate of visceral functions (circulation and respiration) lags behind the mobilization rate of skeletal muscle (musculoskeletal system). Skeletal muscle activity increases dramatically, leading to a surge in oxygen demand, but the visceral system exhibits physiological inertia, and the oxygen supply cannot temporarily meet the demand. At this point, skeletal muscle is forced to utilize some anaerobic glycolysis, resulting in the production and accumulation of lactic acid, disrupting the acid-base balance of the internal environment, and producing a series of uncomfortable or even painful sensations such as chest tightness, palpitations, shortness of breath, and muscle soreness.

After reaching the point of exhaustion, as long as you continue exercising, the mobilization of internal organ functions will gradually improve. With the increase in lung ventilation and stroke volume, oxygen supply gradually catches up with oxygen demand, lactic acid entering the bloodstream is neutralized by buffer substances, the discomfort gradually lessens and disappears, breathing becomes even, and movements regain lightness-this is the state of "rejuvenation." The phenomenon of reaching the point of exhaustion is particularly pronounced during high-intensity exercise. However, with sufficient warm-up and a gradual increase in intensity, the time to reach the point of exhaustion can be significantly shortened, and even significant pain may be avoided.

The steady state follows closely. The steady state can be divided into "true steady state" and "false steady state." In a true steady state, the body's oxygen uptake basically meets its oxygen demand, energy supply is mainly through aerobic oxidation, lactic acid production is minimal, and the body can maintain exercise for a long time. The exercise intensity chosen for weight loss (20%–40% of heart rate reserve) is a typical example of true steady state exercise, ensuring the highest proportion of fat oxidation. A false steady state, on the other hand, occurs when oxygen uptake consistently fails to meet oxygen demand. Although there may be a period of functional stability, as lactic acid accumulates, the body's exercise capacity eventually collapses, leading to premature termination of exercise.

It is important to be aware that physiological "limits" must be distinguished from pathological symptoms. Patients with chronic cardiovascular diseases, such as coronary heart disease, experience chest pain and tightness during exercise due to insufficient blood supply to the coronary arteries. These symptoms will worsen with continued exercise and will not subside. If such individuals experience a persistent increase in discomfort during exercise, they should immediately reduce the intensity, gradually stop exercising, and seek medical intervention.

The "recovery phase" after exercise is equally crucial. After exercise, the body's metabolic rate doesn't immediately drop to a resting state but remains high for a period. Sufficient cool-down activities (relaxation exercises) help the body effectively eliminate metabolic waste and prevent blood from pooling in the lower limbs. In summary, a scientific approach to weight loss through exercise is not only about how many calories are burned, but also about whether a reasonable pace is maintained to allow the body to smoothly transition through the initial "working state" and remain in the highly efficient fat-burning zone of a "true steady state" for an extended period.