## 2 Materials and Methods
### Intervention  
The participants received a set of instructions related to bed mobilization, as well as light exercises and were asked to perform them during the hospitalization. Patients were trained by a physiotherapist at the time of hospitalization, received a written physiotherapy program and had the possibility to contact the team members by telephone or internet-connected smartphone applications for questions and for the communication of their health status. Patients were encouraged to report any adverse events during exercises, such as dizziness, dyspnea, and oxygen deprivation. Depending on the evolution of the patient's state of health, the physiotherapist gave indications to the patient to introduce new exercises from the list or to decrease the number of exercises.  
The RR plan through physiotherapy included systematic posture changes that optimized ventilation and improved gas exchange by promoting alveolar interdependence, passing through lateral decubitus and semi-dorsal decubitus positions. The RR plan also included dyspnea control techniques, slow exhalation techniques for patients who did not easily desaturate, techniques that reduce respiratory rate, breathing coordination techniques, and musculoskeletal exercises for upper and lower limbs.  
During the 14 days of hospitalization, the patients underwent a program of respiratory physiotherapy and physical reconditioning, with a minimum duration of 15 min per day but not exceeding 60 min, depending on dyspnea, oxygen saturation, heart rate and respiratory rhythm. Each phase of RR was performed under the supervision of the medical team, with the aim of gradually achieving the level of independence during the exercise.  
The physiotherapy program included:  
* (PT1) Patients were advised to change their body positions every two hours during the day, going through prone, semi-dorsal, and lateral decubitus. Changing the patient's position reduces the development of bedsores and can reduce the degree of dyspnea. Prone position ventilation: patients with severe COVID-19 with PaO2/FiO2 less than 150 mmHg at 16 h per day;
* (PT2) Lying on the bed (supine position) with head on the pillow at a 45-degree position of the bed, the patient slowly performs the clenching of the fist and fingers and relaxes, and the planar-dorsal flexion of the ankles (10 times slowly);
* (PT3) From the supine position with head on the pillow at a 45-degree position of the bed, the patient slowly performs the flexion-extension of the elbows (10 times slowly);
* (PT4) From the supine position with head on the pillow at a 45-degree position of the bed, the patient slowly performs the flexion-extension of the knees, without lifting the sole of the floor (10 times, slowly);
* (PT5) From the supine position, with head on the pillow at a 45-degree position of the bed, the patient slowly performs lifting and lowering the shoulders, abduction, and adduction of the scapula (5 times);
* (PT8) General exercises. The patients are advised to: squeeze their shoulder blade (8 to 12 times); strengthen the lower legs (10-20 times); raise the heels (20 times); lift the knees, hold for 10 s (3-5 times); shift weight, hold for 10 s (3-5 times); get a single leg balance.  
Out of the 45 included patients, 20 were unable to fill the whole protocol and were assigned to the group of mild physiotherapy (from them, 7 followed only PT1-PT3, while 13 followed PT1-PT5). The remaining 25 patients followed the complete protocol (PT1-PT8), being assigned to the group of active physiotherapy.