Effects of a Physical Rehabilitation Program on Long COVID

The objective is to analyze the clinical, functional, and laboratory effects of a rehabilitation protocol aimed at patients with long COVID. This is an experimental analytical study of the uncontrolled clinical trial type conducted in accordance with the TREND recommendation. The present study was conducted at the Cardiorespiratory Diseases Outpatient Clinic (UEAFTO/UEPA). The Cardiorespiratory Diseases Outpatient Clinic is located at UEAFTO, part of UEPA, in the city of Belém. The clinic integrates teaching, research, and outreach activities and serves as a reference center for the clinical and multidisciplinary care of patients with cardiorespiratory diseases, including infectious diseases, referred from the state public health system. Clinical muscle and functional assessments were performed at this facility.

The collection and analysis of biological material (blood samples) were performed at the Clinical Analysis and Cytopathology Laboratory (LAC), located at UEPA, in the city of Belém, within the Center for Biological Health Sciences (CCBS), which performs various laboratory tests, contributing to scientific knowledge through collaborative studies and projects with the institution's academic community.

The multidisciplinary rehabilitation program consisted of 20 in-person sessions, each lasting 50 minutes, divided into four phases of progressive load. All sessions were structured in three stages: warm-up, training proper, and cool-down. The warm-up consisted of 10 minutes of stretching exercises. During the training stage (30 minutes), participants walked on a treadmill for 15 minutes, with intensity controlled by reserve heart rate (HR), progressing from 50% (sessions 1-5) to 60% (6-10), 70% (11-15), and reaching 80% in the final sessions (16-20). Respiratory muscle training (RMT) was performed with an initial load of 25% of Maximum Inspiratory Pressure (MIP), progressing to 30% starting from the 11th session, with variations in volume ranging from 3 sets of 12 repetitions to 4 sets of 15 repetitions throughout the phases. Resistance training for the upper limbs (vertical bench press and front pull) and lower limbs (leg extension machine and 180° leg press) followed a load progression from 55% to 70% of one-repetition maximum (1 RM), with a gradual increase in the number of repetitions (10 to 15). Finally, the cool-down consisted of 10 minutes of seated rest, incorporating diaphragmatic awareness exercises for metabolic and respiratory recovery.

The primary outcomes were changes in handgrip strength (HGS) and the 6-minute walk test (6MWT) from the 1st to the 20th visit. Secondary outcomes included changes in the functional status scale score, pain tolerance threshold (pressure algometry), and percentage of muscle mass and fat mass (bioimpedance), assessed at the beginning and end of the 20 visits. At the initial assessment, sociodemographic data such as sex, age in years, place of birth, education, marital status, and income in minimum wages were collected.

Hand Dynamometry Handgrip Strength (HGS) was assessed using a CROW model hydraulic hand dynamometer. The test was performed according to the recommendations of the American Society of Hand Therapists (ASTH). The participant was asked to perform a maximum contraction for three seconds for each hand.

Six-Minute Walk Test (6MWT) The 6MWT reflects the functional level of patients for performing daily physical activities. For this, the patient will walk in a flat corridor, 30 meters long, as far as possible. They must go back and forth along the corridor for 6 minutes. Through the distance covered in 6 minutes (6MWT), it will be possible to assess the functional exercise capacity in patients with long-term COVID-19. The test was performed according to the recommendations of the American Thoracic Society (ATS) and the reference equations were used as a normality parameter.

Functional Status Scale The functional status of patients with long-term COVID-19 was assessed using the Post-COVID-19 Functional Status Scale, which evaluates the degree of dependence and disability by assigning scores on five scales: grade 0 (No functional limitations); grade 1 (Insignificant functional limitations); grade 2 (Minor functional limitations); grade 3 (Moderate functional limitations); and grade 4 (Severe functional limitations).

Pressure Algometry Pressure algometry was assessed using a Meddor+ digital algometer (Med.dor - Pressure Algometer, Governador Valadares, Brazil) which was positioned on the anterior deltoid, vastus medialis, and vastus lateralis muscles, exerting an increasing and constant pressure of approximately 1 kg/s until the patient reported pain. At this point, pressure was no longer applied, and the device recorded a Pressure Pain Threshold (PPT) value. It was considered that the lower the PPT value, the lower the pressure pain tolerance threshold, and thus, the patient has greater pain sensitivity. The assessment included measurements obtained from the anterior deltoid muscles (right and left), vastus medialis (right and left), and vastus lateralis (right and left).

Bioimpedance Body composition was analyzed using a digital bioimpedance scale, model HBF - 514C (Omron Healthcare Co Ltd, Kyoto, Japan). The patient was asked to step onto the scale without metal jewelry, barefoot, distributing weight evenly, and remain upright and still until the measurement was completed. The percentages of muscle mass and fat mass were used for the analyses in this study.

Laboratory Tests Blood will be collected from all patients selected for the study via peripheral vein puncture, in 6 tubes of 5ml. Laboratory evaluation will include the following measurements: red blood cell series: Red blood cells, Hemoglobin, Hematocrit, Mean Corpuscular Volume (MCV), Mean Corpuscular Hemoglobin (MCH), Mean Corpuscular Hemoglobin Concentration (MCHC), Red Cell Distribution Width (RDW); muscle function: Creatine Kinase (CK), Lactate Dehydrogenase (LDH) and inflammatory markers: Erythrocyte Sedimentation Rate (ESR), C-Reactive Protein (CRP), Ferritin).