The present study aimed to analyze self-reported consequences after COVID-19 and possible changes in body composition and cardiorespiratory fitness after 1 year. The main results observed were (i) the most recurrent persistent symptoms were related to memory deficits, fatigue, difficulty concentrating, dyspnea and capillary loss, although there were no differences between disease severity; and (ii) increase in LM, SMM and FFM in the severe/critical group after 1 year; (iii) a group effect with lower BF values in the mild FM group compared to the severe/critical group; (iv) increase in Bruce test distance only for the severe/critical group after 1 year; (vi) group effect for DBP post-Bruce test with lower values for mild group compared to moderate and severe/critical groups. No significant differences were observed for anthropometric and other ergospirometric and hemodynamic variables.
Long symptoms of COVID
Persistent symptoms of COVID-19 require early intervention to minimize possible complications of varying severity of symptoms, i.e. mild, moderate and severe/critical patients with follow-up. Asymptomatic patients also require follow-up, especially those with any vulnerable condition or associated comorbidities, combined with multidisciplinary action to promote better outcomes, given the reported outcomes22,23.
Body composition responses in long-term patients with COVID
Patients with greater LM loss 6 months after infection with COVID-19 failed to restore muscle health24and unplanned hospitalizations tended to promote decreases in upper extremity muscle strength, LM, extremity muscle strength, maximal isometric handgrip strength, and one-repetition maximal extensor chair25,26. Tall patients with COVID-19 also have reduced LM compared to a control group (without a diagnosis of COVID-19)23. However, the present study showed increased LM, SMM and FFM for severe/critical patients after 1 year. Discrepancies in measurement time between the present study and others may justify this finding. Therefore, current study participants needed medical clearance to perform submaximal exercise testing, and recovery time will depend on each patient and possible limitations.
The recovery period after infection is susceptible to various complications, especially with different immunological signatures that open an “immunological window” allowing the development of complications such as acute myocardial infarction and myocarditis, among other clinical manifestations27,28. Therefore, morphophysiological parameters were collected after recovery from the acute sequelae recorded in the sub-division of symptoms (mild, moderate and severe/critical). Another study showed that long-term COVID-19 patients showed significant improvement in muscle strength, mobility, and cardiorespiratory fitness after 12 months of in-person physical therapy rehabilitation29.
Previous studies found that BF was higher in patients with persistent COVID-19 compared to controls (ie, without a diagnosis of COVID-19), and outpatients had lower FM compared to patients hospitalized for COVID-19 with the same BMI9.26. Whereas the difference in FM between groups persisted after 1 year (mild with lower FM vs severe/critical cases), actions to ensure improvement in body composition, with reductions in FM, BF and increases in LM, remain essential to improve body composition in survivors of COVID-19. Concomitant training may be a suitable strategy to improve health-related physical fitness by increasing muscle strength, cardiorespiratory fitness and LM, in addition to reducing FM30. Rehabilitation sessions through aerobic and resistance exercises should control the volume, intensity, density, frequency and progression based on each clinical case, as well as the physical fitness indicators that were most affected by the disease20,30.
Cardiorespiratory responses in long-term patients with COVID
VO2 peak, peak HR and RPE did not differ between groups and there was no difference between times (at baseline vs after 1 year), suggesting that the intensity is similar. Significant differences have previously been found between outpatients and severe/critical patients9. The lack of differences between groups in the present study may be related to a reduction in endothelial damage during recovery and subsequent return to daily activities for severe/critical patients9.31. However, the self-reported level of physical activity of patients with different symptoms did not differ.
Bruce test distance increased in the severe/critical group at 1 year, indicating an improvement in physical fitness and a possible reduction in prolongation provoked by COVID-19 survivors. Similar responses were identified in another study, with a significant increase in distance covered in the 6-minute walk test 12 months after hospital discharge30. In the current study, less than 50% of patients (mild, moderate and severe/critical) reported being physically active, ie. > 150 minutes of physical activity/week. However, the improvement in the cardiorespiratory fitness of the patients was also associated with the physical recovery of the individuals who returned to their respective daily activities, in addition to the possible reduction of residual inflammation and organic damage (this condition was not analyzed in the present study).9.31.
Considering the increased distance covered during the Bruce test, there was also an interaction with higher values for RQ of severe/critical patients after 1 year, suggesting an improvement in high exercise tolerance for a long time justified by the increased intolerance to exercise intensity29. Final SpO2 the post-Bruce test showed a group effect with significantly lower values for severe/critical patients, which may be related to chronic hypoxemia after exercise or even to vascular and pulmonary changes and decreased lung function10,31,32.
The main signals that influence respiratory control arise from the response of peripheral chemoreceptors and mechanoreceptors, in addition to the abnormal muscular effort of the pectoral muscles and the decrease in pulmonary compliance that increases the dyspnea that affects performance on exertion33. Cardiorespiratory rehabilitation of these patients requires SpO monitoring2blood pressure and cardiac function in addition to applying the principles of volume-intensity interdependence, increasing workloads, biological individuality, and periodic assessments to evaluate outcomes and mitigate possible consequences of COVID-1934.
Blood pressure responses in long-term patients with COVID
DBP post-Bruce test also differed among patients with long-term COVID-19, with higher values for the moderate and severe/critical group than for the mild group. DBP response during exercise was associated with comorbidities (prevalence of obesity, systemic arterial hypertension, diabetes mellitus, and tobacco use) but was not independently associated with a higher risk of death from cardiovascular disease35. A systematic review with meta-analysis found that SBP ≥ 210 mmHg for men and ≥ 190 mmHg for women at moderate exercise intensity can be considered an independent risk factor for cardiovascular events and increased mortality36. The physiology and pathophysiology of DBP after exercise are not yet fully understood, and increases in DBP may be associated with greater peripheral arteriolar resistance, increased afterload, and even arterial stiffness or dysfunction and early signs of atherosclerotic vascular disease35.
A high DBP response to exercise is a predictive factor for increased systemic arterial hypertension. Because systemic arterial hypertension can often be asymptomatic, patients can progress to structural and/or functional changes in target organs and endothelial dysfunction, with an imbalance between vasodilator and vasoconstrictor substances affecting vascular function, with reduced blood pressure capacity of the large arteries , damaging pressure homeostasis37,38. A study observed a significant increase in SBP and DBP in men and women during the pandemic period (between 2019 and 2020).39, possibly related to increased alcohol consumption, weight gain, lower level of physical activity, emotional stress and less prolonged medical care (with reduced adherence to treatment), although the parameters above were not observed and/or measured in the present study, as the collections were made strictly during the pandemic period. However, an increase in SBP during exercise is a normal response related to the intensity of the effort40.
Limitations, strengths and future directions
This study has some limitations. First, the lack of follow-up during the acute infection of patients is justified by exercise intolerance. Second, there was no follow-up at 1 year between assessments and changes in behavior (eg, physical activity and dietary habits) and other characteristics not available in the study may be associated with improvements in body composition and cardiopulmonary fitness in hospitalized groups . Third, loss to follow-up at the second assessment may have influenced the results; but loss rates were similar in all groups. Unfortunately, these patients chose not to return for re-evaluation and this was related to (i) lack of time; (ii) misunderstanding the need to perform a reassessment; (iii) patients believe they have fully recovered from COVID; and (iv) lack of financial resources to travel to university and lack of part-time employment. Given the future research outlook, patients can be evaluated over months and even years to understand pathophysiological responses. Additionally, actions that seek to assess, intervene, and reassess patients with long-term COVID associated with a control group (without the disease) may direct more assertive rehabilitation actions.
Given the clinical importance, some points can be highlighted: (i) hospitalized patients should be monitored periodically for body composition, cardiorespiratory fitness and vital signs; (ii) all survivors of COVID-19, regardless of disease severity, may be observed for fatigue, dyspnea, muscle pain, joint pain, dizziness, tinnitus, sensation of hearing loss, otalgia, ageusia, anosmia, deficit of memory, difficulty concentrating and capillary loss and (iii) earlier interventions with health professionals can reduce the possible impacts (sequelae) of COVID-19.