Exercise risk assessment and stress testing: ECG monitoring, termination criteria and safety assurance system

In the practice of guiding physical fitness activities, a series of indicators under resting conditions can be used to assess a person's health status and athletic ability. However, the measurement of indicators under resting conditions has certain limitations in assessing athletic ability and health status, and it cannot reveal the degree of the body's response to exercise under exercise conditions. Many indicators reflecting health status may be normal under resting conditions, but may appear abnormal under exercise conditions. An exercise load test involves conducting exercise under certain exercise load conditions, observing the body's response to the exercise, and using instruments to record the various response signals produced by the body to determine the person's health status and test athletic ability.

Depending on the instruments used and the recorded indicators, there are various methods for exercise stress testing. The most commonly used is exercise electrocardiography (ECG), and maximum oxygen uptake measurement is essentially a type of exercise stress test. In the practice of guiding physical fitness activities, exercise stress testing is a necessary condition for designing exercise prescriptions. Exercise stress testing on obese patients can obtain the following information: indications of cardiac function and exercise capacity; an appropriate and safe range of exercise intensity; whether there are serious pathological changes in the cardiovascular system that affect exercise capacity; and cardiac reserve capacity.

Before an exercise stress electrocardiogram (ECG) test, a detailed medical history, physical examination, and certain medical tests should be conducted on the subject. The selection of the initial load and the magnitude of the increasing load are determined based on the subject's gender, age, health condition, and exercise capacity. Based on the needs of exercise stress testing in community fitness activities, we designed an exercise stress test step suitable for the elderly. The step is 20 cm high, 40 cm wide, and 60 cm long. Level 1 load involves climbing up and down the steps 15 times per minute, while Level 2 load involves climbing up and down the steps 30 times per minute. Level 2 loads generally meet the needs of exercise stress ECG testing for the elderly.

Exercise stress testing is also a form of exercise, with intensity gradually increasing. For patients with chronic cardiovascular diseases, there are certain risks associated with exercise. Therefore, it is important to be aware of contraindications for exercise stress testing, such as: significant abnormalities on a resting electrocardiogram (ECG) indicating a definitive diagnosis; a history of angina attacks within the past two weeks; severe hypertension; severe hyperthyroidism or hypothyroidism; mid-to-late pregnancy; diabetes mellitus complicated by severe atherosclerosis and acidosis; and acute infectious diseases. Criteria for terminating exercise stress testing include: diagnostically significant ECG findings, such as arrhythmias, ST segment depression exceeding 0.1 mV, and T wave flattening or inversion.

In addition, the test should be terminated immediately if blood pressure rises significantly above the target level or drops significantly, causing chest pain, chest tightness, palpitations, difficulty breathing, or reaching sublimit heart rate, or if the subject is unable to continue or requests to stop. During the exercise stress test, a designated person must closely observe the subject's facial expressions, observe and record the electrocardiogram, and measure blood pressure. The increase in load should follow a gradual approach. Subjects with a confirmed diagnosis of chronic cardiovascular disease may be exempt from the exercise stress test; if they insist on undergoing it, the load should begin at 0 watts or 2 km/h.

Exercise stress testing laboratories should be equipped with necessary resuscitation equipment, supplies, and medications, and at least one qualified cardiovascular clinician should be present. After the exercise stress test is stopped, the subject should be observed in the laboratory for at least 30 minutes, and a 12-lead resting electrocardiogram should be recorded before leaving. Progressive exercise electrocardiography is a crucial component of exercise risk assessment, as exercise risk primarily occurs in adults with pre-existing cardiovascular and metabolic chronic diseases. Reports suggest that over 95% of exercise-induced sudden cardiac death occurs in patients with coronary heart disease and myocarditis.

A normal resting electrocardiogram (ECG) does not necessarily mean normal heart function. While coronary atherosclerosis restricts blood supply to the myocardium, if the plaque size and extent do not significantly limit resting myocardial blood flow, the ECG may not show any obvious positive findings. However, when exercise of a certain intensity increases myocardial oxygen demand, and coronary blood flow cannot meet the myocardial needs, myocardial ischemia and hypoxia will occur, causing changes in the ECG. Therefore, exercise stress testing can reflect the safe exercise intensity for obese patients.

During progressively increasing exercise load, the energy supply system of skeletal muscle contraction gradually changes. At low intensity, energy is primarily supplied by the aerobic oxidation of glucose and fat. As intensity increases, anaerobic glycolysis of muscle glycogen begins to be utilized. As long as anaerobic glycolysis is involved, the proportion of energy supplied by fat oxidation gradually decreases. Therefore, the anaerobic energy supply system is not required during exercise for weight loss. Exercise load testing can determine the optimal exercise intensity to achieve the best weight loss results.