The most common greeting that patients hear in hospitals is: get some rest and wish you a speedy recovery. The traditional concept of illness is always associated with rest. The medical term for rest is called braking, which includes: bed rest (a common measure when hospitalized for various injuries and illnesses), local immobilization (commonly used when fractures or dislocations occur), etc. The purpose of rest is to protect the body’s health. However, rest does not always facilitate recovery. Here we will talk about the other side of rest. Let’s start with cardiovascular disease. Many patients use bed rest at the onset of the disease. It is not known that bed rest for a few hours will significantly increase the volume of urine, resulting in reduced blood volume, lower cardiac output, and increased blood viscosity, making angina, thrombotic vasculitis, and venous thrombosis significantly more likely to occur or flare up. Cardiovascular patients often have episodes at night, which are not unrelated to these secondary reactions. From a clinical perspective, patients with heart failure require a sitting position to reduce the burden on the heart, so why must they remain in the prone position during other cardiovascular episodes? Modern rehabilitation for myocardial infarction actually begins with the adoption of the sitting position. Many patients fear that physical activity will cause myocardial rupture or aggravate heart damage. In fact, the energy consumption of activities such as eating, washing, brushing teeth, dressing, and walking slowly is only 20% to 50% higher than that of bed rest, while the regulating effect of scientific and moderate exercise on psychological and mental states cannot be replaced by passive bed rest and simple drug therapy. The next thing to talk about is respiratory disease. Many people think that bed rest can reduce respiratory distress during an attack of respiratory disease. In fact, the ratio of pulmonary ventilation to blood perfusion tends to be imbalanced in the recumbent position, with the result that the exchange between alveolar gas and blood is limited. Also the movement of the diaphragm is restricted in the recumbent position. It is for this reason that patients with respiratory diseases often prefer the semi-recumbent or seated position to the flat position. In addition prolonged bed rest can lead to an increased incidence of pneumonia. The effects of rest on the bones and joints are also very significant. Bone growth and bone density depend on the forces exerted on the bone. This is the reason why fish in water have significantly lower bone density than mammals on land. Once the bone loses its external force, it does not need a strong texture, so osteoporosis occurs. Astronauts face a major issue is how to prevent weightlessness caused by osteoporosis. And clinically, patients, whether bedridden, fixed fractures or after neurological paralysis, commonly have varying degrees of osteoporosis. Osteoporosis in middle-aged and elderly people is also closely related to lack of physical activity. For this reason, proper exercise is extremely important to maintain bone density. Joint cartilage relies heavily on pressure to exchange nutrients. If the joints are not stressed for a long time, the cartilage will become malnourished, resulting in cartilage degeneration and joint dysfunction. Muscle atrophy and loss of muscle strength are the most common consequences of rest. In healthy individuals, bed rest for one month can reduce the muscle fiber cross-sectional area by 10% to 30%, and by 50% in two months. The rate of muscle strength reduction is 10% to 15% per week, and up to 50% muscle strength reduction in 3-5 weeks. In fact, there are also intrinsic metabolic changes in the muscle. For example, bed rest for 3 days can cause a rapid decrease in muscle insulin receptor sensitivity and a decrease in glucose tolerance, which is an important cause of type 2 diabetes in adults. Studies have already shown that 1 day of bed rest results in a loss of exercise capacity equivalent to the amount of motor function decline in older adults for 1 year. Appropriate exercise or activity is central to rehabilitation, but excessive exercise can also be detrimental to health. Whether to exercise or brake after an illness needs to be treated differently according to the patient’s condition, which is also a reflection of the art of rehabilitation treatment. The truth that movement is appropriate and things are inevitable needs to be grasped and understood scientifically in our daily lives.