In order to control the spread of SARS-CoV and the development of the epidemic, glucocorticoids were widely used in the emergency treatment of SARS, so many patients developed symptoms of femoral head necrosis, as well as pulmonary dysfunction and other side effects of drugs. As one of the main means of pulmonary rehabilitation training, sports rehabilitation was of great significance for the improvement and recovery of patients with acute or chronic lung injury. Pulmonary function was one of the most important detection methods to evaluate the degree of disease, clinical symptoms, prescription efficacy, prognosis recovery and psychological status. In the clinical work of rehabilitation, a large number of patients who are bedridden or receive mechanical respiration should receive rehabilitation treatment based on safety assessment. Lau‘s team ^[14][42] recruited 133 patients recovering from SARS that only received physical therapy to observe the cardiopulmonary and skeletal muscle performance of the patients. Physical improvement was evaluated through walking, strength training, tummy and push-up tests over a six-week period, and the results showed that the exercise training program was effective in improving the cardiorespiratory and skeletal muscle health of SARS patients. In the protection of life under the condition of steady state stable, to increase the chance of sit down and rise up, the bed movement and activities were widely applied in clinical, letting patients facilitate from passive to accept early motion to independently complete the movement; the rehabilitation exercise positively improved the disease condition in patients with early, middle, critical period, and disease after preoperative, postoperative and the outcome of the entire process. SARS patients generally had mechanical bed rest treatment for about one month, and the main symptoms in the convalescent period were fatigue, easy fatigue, fast resting heart rate, and obvious shortness of breath after light exercise, which were closely related to the damage of bed rest and the disease itself to the body, especially the lung function damage. In the recovery period of most SARS patients, systemic joint pain symptoms appeared, and bone ischemia and necrosis was relatively common, and its prevalence was greatly related to the excessive use of hormones during treatment ^[15][16][43,44]. Case observation of nine medical workers infected with SARS in Dongzhimen Hospital of Beijing University of Chinese Medicine, showed that hormone-induced femoral head necrosis usually manifested as kidney deficiency. According to Wang ^[17][45], poor renal function could lead to a poor blood flow and lead to ischemic necrosis of the femoral head. Oral Chinese medicine intake, external Chinese medicine foot soaking, physiotherapy and hyperbaric oxygen therapy could relieve blood vessel pressure, improve microcirculation, accelerate tissue repair, and increase blood oxygen tension. During rehabilitation period, knee extension/flexor muscle strength exercise and light aerobic exercise had a good effect on patients’ recovery. Through peripheral and central effects, physical strength could be enhanced, oxygen utilization efficiency of skeletal muscle also could be improved ^[18][46]. For patients with severe lung injury, the peripheral effect should be the main aerobic exercise, supplemented by the central effect. Sub-extreme exercise was reported to reduce the symptoms of palpitation and shortness of breath, improve cardiopulmonary dysfunction, and play a key role in improving cardiac output, stroke volume, vital capacity and lung capacity ^[19][20][47,48]. Shen et al. ^[21][49] observed 148 cases of SARS of five hospitals in Guangzhou, and showed that 106 cases of upper extremity ischemia necrosis had used hormones in the treatment of SARS, and a few cases closely related to the cumulative dose of hormone and bone avascular necrosis, whereas 42 cases of osteonecrosis patients who did not apply hormone therapy had no bone necrosis. In patients with abnormal chest X-ray or lung CT, some of them have aggravated symptoms such as chest tightness, shortness of breath and dyspnea after activity, so they could not participate in more vigorous physical activities, and all indicators of life should be monitored at all times ^[22][50]. Using acupuncture and moxibustion therapy recommended by He, lung inflammation absorption and pulmonary fibrosis was treated; taking advantage of collection of acupuncture moxibustion gained better effects. This method was implemented in the SARS rehabilitation clinic of Beijing Hospital of Traditional Chinese Medicine, and the symptoms of fatigue of the discharged patients were obviously ameliorated, and the curative effect of improving the health quality of life was evaluated objectively ^[23][21].

2.3. Psychological Situation

To face the “SARS sequelae” left behind due to treatment and prevention, excessive use of hormones leaded to lifelong pain and sufferings, causing great harm to patients’ body and mind, and psychological treatment was essential. In July 2003, an investigation on the patients who had recovered from SARS in Guangdong Hospital of Traditional Chinese Medicine showed that ^[24][51] most of the patients had pulmonary lesions and other sequelae, especially the psychological barriers caused by discrimination. Zhong, an academician, said that psychological problems were the biggest sequelae of SARS ^[25][52]. Wang et al. ^[26][53] investigated the psychological status of 103 cured SARS patients in Guangzhou after recovery, and the results showed that people’s low awareness of SARS led to patients’ fear and rejection psychology, which had a great impact on social relations and interpersonal communication after recovery. Some patients thought that they would be discriminated by the society after the disease, which would lead to a kind of hostility. At the same time, they were afraid that they would spread the disease to their families and friends, which would also lead to depressive behaviors ^[27][54].

According to a private survey, Beijing registered a total of 300 patients with “SARS sequelae”, among whom 80% had left their posts due to illness and 60% had family accidents ^[28][55]. Depression was almost a common condition among patients recovering from SARS, and they did not receive timely counseling and treatment, which had a very negative impact on their lives. In July 2003, the survey of 69 SARS survivors of Guangdong hospital, showed that 57.97% of the patients with poor mental state, memory drops, 49.3% of the patients reduced work ability and increased scruples in the future work and life, 40.58% of the patients with easy irritable, 20% of the patients fear or feeling alone, but 100% of the patients got family and friends’ concern and support ^[29][56]. To fight against diseases, we should maintain a good mental state, pay attention to mental health, nutritional support, and health protection, establish the determination to overcome the disease, and eliminate anxiety, anxiety, depression and other negative emotions. At the same time, it is also very important for the government to improve some institutional guarantees, establish a complete information tracking file for SARS patients, and keep a close eye on the life and health of the “SARS sequelaa”.

3. Implications for COVID-19 Exercise Rehabilitation in China

In combination with the pathological research results of COVID-19 in the medical field, relevant studies have elaborated the main principles of strengthening physical exercise to effectively prevent COVID-19 ^[30][57]. First of all, moderate physical exercise can promote blood circulation, let the immune cells timely transport and destroy the virus in the body, which is the main basis for physical exercise you effectively resist and contain coronavirus ^[31][58].Secondly, increasing the activity of angiotensin converting enzyme (ACE) in the renin-angiotensin system (RAS) during exercise improves the structural adaptability of coronary artery tree, which can effectively resist SARS-CoV-2 and play a positive role in the mechanism of acute myocardial injury caused by COVID-19 ^[32][59]. Third, sedentary living at home can lead to muscle fixation, damage and deterioration of mitochondrial stability, and cause organic and systemic inflammation, which is also an important mechanism of COVID-19 pathogenesis ^[33][60]. Finally, the study also confirmed that physical exercise effectively counteracts and reduces the negative effects of COVID-19 on people’s physical and mental health ^[34][35][5,61]. Lung function injury greatly reduced patients’ daily activity ability and fatigue degree, pulmonary rehabilitation training was urgently needed to restore the lung function. Liu et al. ^[36][62] conducted a 6-week respiratory exercise intervention and rehabilitation treatment on 36 elderly patients with COVID-19 who were over 65 years old without related basic diseases, and the results showed that respiratory exercise could effectively improve the patients’ respiratory function, quality of life and anxiety, providing an important reference for clinical treatment. Investigations showed that more than 75% of COVID-19 hospitalized patients required oxygen therapy, approximately 54% developed respiratory failure, and more than 30% required mechanical ventilation to maintain pulmonary gas exchange. However, prolonged mechanical ventilation can lead to atrophy of the diaphragm and rapid development of systolic dysfunction, leading to the risk of ventilator (diaphragm) weakness and difficulty in getting COVID-19 patients off the ventilator ^[37][63]. Participated in related studies have shown that advance moderate endurance exercise, the infection will be after the coronavirus to accept ventilator support, from the endurance exercise induced by the diaphragm preadaptation benefit, endurance exercise can increase the superoxide dismutase (SOD) in the diaphragmatic muscle mitochondrial protein 2 (SOD2) level and the amount of heat shock protein 72 in cytoplasmic protein, promote the diaphragm of biochemical changes, effectively resist COVID-19 induced sepsis complications related to ^{[37][38][39][40]}[63,64,65,66]. One thing the needs to be noted is that, in nursing work, a large number of patients who were bedridden and receiving mechanical breathing needed to receive rehabilitation treatment on the basis of safety assessment. Before the formal implementation of sports rehabilitation training, it was necessary to evaluate the symptoms, sports ability, quality of life, mental state and other aspects. Bansal’s team ^[41][67] evaluated the performance of 20 adults with disordered breathing on an incremental cardiopulmonary exercise test. It found that VO₂max was lower than average and that patients more frequently cited dyspnea as the cause of their exercise limitations. However, due to the specific cultural, historical and geographical background in China, the exercise rehabilitation of COVID-19 had its own requirements and characteristics. Similarly, the illness severity pattern was divided into four groups: asymptomatic infected patients, symptomatic patients isolating at home symptomatic patients admitted to hospital, and symptomatic patients requiring ventilator support in critical care. Here, we concluded COVID-19 patients’ exercise rehabilitation strategies in three stages of clinical treatment, restoration, and remote healthcare, and divided clinical patients into two groups of patients with mild disease, critically ill patients, and list specific exercise rehabilitation strategies recommendations accordingly in Figure 1.

Figure 1. The comparison of symptoms caused by COVID-19 and SARS and implication on rehabilitation strategies of COVID-19 in China.

3.1. Clinical Exercise Rehabilitation Methods for COVID-19 Patients

Mild patients can receive moderate to low intensity aerobic training under the condition of cardio-respiratory tolerance, that is, 40% to 60% of the maximum heart rate (HRmax) and during the training, the heart rate, blood oxygen saturation, and respiratory rate should be monitored. The choice of exercise mode can be indoor treadmill exercise, alternate steps, stepping, squatting, rope skipping and other aerobic exercises. According to relevant reports, the mobile cabin hospitals in Wuhan organized patients with mild COVID-19 to do square dancing, breathing exercises, eight-section brocade Chi Kung, and Tai Chi exercises, which not only improved the cardiopulmonary function and reduced the incidence of complications, but also relaxed the anxiety of patients ^[42][13]. The First Affiliated Hospital of Fujian Medical University designed an exercise program named “Eight Segment Pulmonary Rehabilitation Exercise” to improve the condition of COVID-19 patients and promote the recovery of their lung and body functions ^[43][68].

For critically ill patients, it is required to strictly monitor the safe implementation of patients’ respiratory rehabilitation on the basis of conventional treatment, and accurately grasp the perfect timing of intervention according to the patient’s condition. The rehabilitation strategy should focus on the patient’s heart rate, blood pressure, respiration, blood oxygen, heart, brain, lung and other organs and the consciousness level of patients. When patients come to a physiologically stable state, intervention and respiratory physiotherapy can be carried out such as posture management (including bedside swinging, lying and sitting, regular turning over and massaging the body and other posture changes) to stimulate the heart, lungs and blood vessels, improve the patient’s blood oxygen transport capacity, and enhance airway status and breathing ^[44][45][46][69,70,71].

For patients with mechanical ventilation, the bed body movement can effectively improve the physical condition and ameliorate complications of patients with sepsis. The amplitude and scope of activities need to be adjusted according to the disease conditions and individual differences. Generally, it is recommended to be active for 10 to 20 minutes, and patients with hemiplegia or shortage of muscle strength, shall execute the exercise with the help of the guidance of nursing staffs.

The specific actions of horizontal rehabilitation exercise ^[47][72] are as follows:

(1)

Relaxation training: lie flat on the bed, relax the whole body muscles, clench fists, feel the muscle tension in the fingers, knuckles, and palms, keep the movement until you feel a slight cramp, then open your hands to relax and rest, repeat five times.

(2)

Abdominal breathing training: the patient presses his hands on the abdomen, and exercises with the abdomen when breathing, breathes deeply through the nose until it can’t breathe in, and then slowly and rhythmically expel the gas from the body, repeat five times.

(3)

Upper limb elevation training: the patient touches the chest, shoulders, chin, ears, and top of the head with the index finger, and then stretches up to the highest point for a few seconds and then recovers, with both hands at the same time.

(4)

Elevating lower limbs training: straighten legs and lift them up until fatigue, assisted by others to continue to rise by 5 to 15 degrees, when the patient feels waist soreness, back muscle tension, slight pain or discomfort, switch to the other leg.

(5)

Hip bridge training: bend the knees in the supine position, put your feet close to your hips as much as possible, use your feet and head as the fulcrum, add elbows if necessary, lift up to arch, feel the extension of the waist and back, hips and lower limbs When you reach your limit height, put it down and hold it up again, repeat 10 times.

(6)

Meridian patting training: the patient pats along the side of the body from shoulder to ankle in turn, alternating up and down, and repeats 10 times.

3.2. Exercise Rehabilitation Methods for COVID-19 Patients after Recovery

COVID-19 inpatients are often accompanied by related basic diseases ^[48][73], so it is important to remember to blindly carry out all kinds of respiratory supportive therapy. On the basis of clarifying the internal mechanism of respiratory exercise and COVID-19, it is an important field to strengthen the research on the intervention of respiratory rehabilitation exercise for patients with related basic diseases or induced complications, which needs to be deepened and solved urgently. The specific methods are as follows: (1) respiratory breathing: inhale deeply through your nose, hold for 2 seconds, and then slowly exhale through a whistle, repeat practice for 15 minutes; (2) long breathing exercises: stand up torso, relax the muscles, inhale deeply, feel the air enter the lower abdominal cavity, then exhale slowly, the slower the better, fully feel the process of the air leaving the lungs, trachea, and nasal cavity, practice 10~20 times every day; (3) bend and exhale exercise: stand with your feet shoulder-width apart, cross your arms in front of your chest, exhale slowly when you bend your body forward, and inhale when your arms fall and spread out to both sides when you recover, stick to it every day at least 20 times. Besides, abdominal breathing can be found in a variety of physical and mental exercises, which can enhance respiratory function, stimulate the vagus nerve and produce a relaxation response, including yoga, meditation and Qigong ^[49][50][74,75]. The technical operation of abdominal breathing is very simple. The subjects consciously move the stomach when inhaling, tighten the stomach muscles, and let them fall inward when exhaling with focusing on the breath and avoiding to hold your breath ^[36][62]. Before training, set the exercise intensity according to the patient’s maximum heart rate, generally controlled at 60–85%, and the exercise time is about 30 minutes (the exercise intensity and time can be adjusted appropriately according to the condition of different patients). During the exercise, the subjects should pay attention to control the heart rate to avoid dizziness, fatigue, shortness of breath, chest tightness, chest pain and other situations. If those situations happen, the exercise program should be stopped immediately. In severe cases, nitroglycerin and other drugs need to be applied.

By cardiopulmonary exercise test (CPET), in the case of load increment, by breathing, circulation, nerve body fluids, such as the metabolic system of participation, patients from resting to gradually restore again to limit state motion data, including heart rate, blood pressure, ecg analysis, such as traditional information, and provide important data with oxygen metabolism as the core, such as: peak VO₂ and minute ventilation/ carbon dioxide production (VE/VCO₂) slope are used to describe in detail the physiological conditions of patients in exercise state through rich and comprehensive monitoring indicators ^[51][76]. Discharged patients still need to pay attention to protection from viruses to avoid secondary infections. After recovery, they will be left with varying degrees of respiratory damage and lung dysfunction, which may cause other organ complications impacting daily life. It is recommended that during the home care period, suitable exercise rehabilitation videos can be utilized on multimedia equipment to insist on carrying out breathing rehabilitation training, such as breathing exercises, Tai Chi, eight-section brocade Chi Kung, yoga and other light exercise training ^[21][52][49,77]. With nutritional support, psychological counseling, and regular follow-up visits, symptoms such as dyspnea, shortness of breath, consolidate can be alleviated, which helps to improve and promote respiratory function, immune system, and exercise capacity. The subjects need to make full use of family, community, and medical resources for systematic and scientific rehabilitation training to lay a solid foundation for returning to society as soon as possible.

3.3. Remote Exercise Rehabilitation Methods for COVID-19 Patients

From the national incidence, about a quarter of the medical personnel are the direct victims of infectious disease. Epidemic prevention and control in the process of health care workers should pay attention to the cultivation of clinical thinking and judgment ability, concept not only stay on the disinfection, isolation and general knowledge, from the technical service extension to community service, and from the hospital service extension to the outside of the hospital service. The treatment and service will be placed in the same important position, penetration in the prevention, treatment, health care, rehabilitation and other aspects. Each country has also established the joint operation of “medical prescription” main attack and “exercise prescription” auxiliary attack. For example, the UK has established a national referral database and intervened in exercise prescription to strengthen the management and treatment of the national health condition ^[53][78]. The principles, content framework and minimum standard baseline for exercise for different populations were developed during the Australian pandemic ^[50][75]. Han University in the Netherlands has established an online service platform to provide the latest exercise prescription and programme support during the COVID-19 pandemic ^[54][79]. The United States has established a remote rehabilitation and testing system including COVID-19 physical and mental health and nursing services ^[55][80]. Japan makes use of TV, Internet, video and other technologies to produce the regular home version of the elderly’s physical function exercise prescription video ^[56][81]. Guidelines on physical activity based on social distance during COVID-19 in Korea ^[57][82]. The Chinese Association of Sports Science has scheduled to set up “Sports Health Promotion Centers” nationwide from 2020 to meet the public’s fitness needs and establish a library of traditional and popular exercise programs.

The majority of the COVID-19 disease outbreak affected the elderly, the majority of which have heart, brain, liver, kidney and other organs complication, and studies have confirmed that traditional project prevention, treatment and rehabilitation for the elderly COVID-19 have a positive effect ^[58][83]. It can promote the recovery of respiratory symptoms, deep, rhythmic breathing and body movement with the concentration of slow, make people relaxed mood, pressure drops into a state of meditation, priority is recommended to use qigong to prevent COVID-19 improve infection after respiratory symptoms ^[59][84]. Qigong can increase the number and activity of human immune cells, reduce inflammatory factors and inflammatory responses in the body, and train specific muscle groups to enhance physical strength through exercise ^[60][61][85,86]. Choosing Ba Duan jin, Tai Chi such delicate, smooth, soft, light movement, slow body movements and musculoskeletal stretch should be combined with body relaxation, deep breathing and mental concentration, emphasize the balance of the body and breath free, drives the whole body movement to increase the health of the body.