Clinical and Functional Effects of Rehabilitation of Patients after COVID-19 Infection

Background/Objectives: The most common post-acute consequences of SARS-CoV-2 include lung dysfunction, the impairment of cognitive functions and mental health, as well as the impairment of the musculoskeletal system in the form of fatigue and muscle weakness. Post-COVID-19 patients often experience impaired balance and reduced physical capacity. It is important to implement a rehabilitation program that eliminates the side effects of COVID-19 and allows for significant improvement in the patient’s functionality. The aim of our study was to assess patient functionality after a 6-week rehabilitation program on balance, foot pressure distribution, and physical capacity in post-COVID-19 patients. Methods: The clinical study group consisted of 53 people 3 months after COVID-19 infection, confirmed by a positive PCR test. Exclusion from the study included people with comorbidities that impaired balance and gait. The patients underwent a posturographic assessment—Romberg test, a baropodometric assessment—static and dynamic, and a performance assessment—a 6 min walk test determining shortness of breath on the mMRC scale, blood pressure, heart rate, and saturation. Patients participated in rehabilitation until the sixth week, after which they were assessed again. Comparisons were made using IBM SPSS Statistics 27.0 software using the Wilcoxon pairwise order test, at a significance level of p < 0.05. Results: The result of the postural control assessment showed an improvement in the ability to maintain the centre of gravity in terms of the foot support area—statistical decreases were observed in the ellipse area, from 745.28 mm2 to 453.52 mm2 (p = 0.009), as well as maximum (from 3133.5 gr/cm2 to 2994.2 gr/cm2; p = 0.065) and average load on the left foot (from 1010.1 gr/cm2 to 969.38 gr/cm2; p = 0.028). In the 6 min walk test before and after exercise, the heart rate decreased after the therapy (shortness of breath on the mMRC scale also decreased from 79.12 to 74.95). This means that patients achieved better physical fitness and efficiency. Conclusions: Rehabilitation significantly improved balance, as measured by a decrease in ellipse area during the Romberg test.


Introduction
Falling sick with COVID-19 results in a number of health hazards not only at the moment of infection but also in long-term sequelae after recovery [1,2].The most frequently observed impairments include impaired respiratory function, cognitive functions, and mental functions as well as muscular functions manifesting themselves through muscle fatigue and weakness, which matters as far as a patient's daily life is concerned [3].Furthermore, other research indicates that it takes seven months for many patients to achieve full recovery, and a failure to do so causes persisting symptoms involving multiple-organ impairment such as impaired systemic functions, cognitive function, or neurological function [4].Reduced physical activity or the lack of it due to a long-term hospitalisation are presumed to cause multiple-organ impairment in the case of individuals suffering from persisting COVID-19 symptoms or post-COVID-19 conditions, which may adversely impact the postural control system, for instance, while rising to an erect posture.The research indicates that post-COVID-19-hospitalised patients show impaired visual and somatosensory cognitive function in terms of erect posture [5].Furthermore, other sources confirm the fact that post-COVID-19 patients obtain lower postural control test results as compared to the control group [6] and differ in terms of the foot pressure distribution as far as baropodometric assessment is concerned [7].The neuromuscular system involves muscles and the nervous system to control movements of the body and maintain postural balance, and COVID-19, impairing that system, may result in long-term sequelae affecting the postural control system [8].To prevent unfavourable post-COVID-19 symptoms, the available literature suggests implementing a hospital rehabilitation program.The results of research on the use of rehabilitation in people who have suffered from COVID-19 and were hospitalized in the ICU show an improvement in balance, muscle fitness, and strength, as well as the functioning of the respiratory system, which improves the quality of everyday life [9].

Purpose
The aim of this study was to conduct the functional assessment of static and dynamic baropodometric and postural control parameters and the physical capacity of patients undergoing 6-week outpatient rehabilitation, including physical efficiency training sessions as well as respiratory and multiple-organ function improvement exercises.The aim of our study was to assess the patient's functionality after rehabilitation.

Methods
The clinical study was conducted at the Rehabilitation Clinic under the consent issued by the Bioethical Commission no APK.002.51.2022 at the Medical University of Białystok.The research was conducted from January 2022 to January 2023.Patients were assessed among people who were referred to a Rehabilitation Clinic for post-COVID rehabilitation.Patients participating in the study were present at each rehabilitation session.The qualified eligible patients were diagnosed at least 3 months prior to the study.At the moment of the study, no post-SARS-CoV-2 side effects were reported.Exclusion from the study included individuals with underlying conditions impairing postural control and gait such as obesity, neuromuscular disorders, neurological deficits or sensory disorders, spinal or lower limb surgery, or injury impairing stability, for instance, 2nd-3rd degree ankle joint sprain as well as the use of crutches, walking sticks, walking frames, etc., for the purpose of daily activities.The exclusion criteria also included smokers without any previous diseases or operations within internal organs such as the respiratory, cardiovascular, and digestive systems.All patients declared that their occupations did not involve physical labour.
During qualification, all patients reported dominance on the right side of both the upper and lower limbs.
Each of the patients issued informed consent to take part in the study and was notified of the effects and course of the study.The study group comprised 53 post-COVID-19 (30 women and 23 men) patients whose diagnosis had been confirmed by the clinical symptom-based examination results and positive PCR test-covering the polymerisation chain reaction (Table 1, Figure 1).
The patients suffered from moderate symptoms of the disease, the prevailing symptoms having been cough, fever, muscle pain, loss of the sense of smell, and taste disorders.The patients suffered from moderate symptoms of the disease, the prevailing symptoms having been cough, fever, muscle pain, loss of the sense of smell, and taste disorders.
The patients underwent functional assessments to the extent of an interview, the assessment of postural control to maintain balance while standing by means of Romberg's test, static and dynamic baropodometric parameters, as well as physical efficiency testing including blood pressure, pulse, and saturation measurement by means of a 6 min walk test.Furthermore, dyspnoea was assessed in terms of the mMRC Scale.Next, for a period of 6 weeks, the patients performed personalised training workout programmes, respiratory exercises, and multiple-organ function improvement exercises, after which they underwent a functional reassessment test procedure.
The training included resistance exercises for the upper and lower limbs, taking into account the movements of flexion and extension, abduction and adduction, as well as internal and external rotation.This was performed in two series, taking into account the number of repetitions at 70% load and the feeling of fatigue on the RPE scale up to 7. Included breathing exercises were based on relaxation exercises, extended exhalation exercises, diaphragmatic breathing exercises, and exercises increasing the respiratory  The patients underwent functional assessments to the extent of an interview, the assessment of postural control to maintain balance while standing by means of Romberg's test, static and dynamic baropodometric parameters, as well as physical efficiency testing including blood pressure, pulse, and saturation measurement by means of a 6 min walk test.Furthermore, dyspnoea was assessed in terms of the mMRC Scale.Next, for a period of 6 weeks, the patients performed personalised training workout programmes, respiratory exercises, and multiple-organ function improvement exercises, after which they underwent a functional reassessment test procedure.
The training included resistance exercises for the upper and lower limbs, taking into account the movements of flexion and extension, abduction and adduction, as well as internal and external rotation.This was performed in two series, taking into account the number of repetitions at 70% load and the feeling of fatigue on the RPE scale up to 7. Included breathing exercises were based on relaxation exercises, extended exhalation exercises, diaphragmatic breathing exercises, and exercises increasing the respiratory movement of the lower ribs, and they were performed in two series-at the beginning and at the end of the therapy, with 10 repetitions each.So as not to lead to the patients' hyperventilation, endurance training was performed on a cycloergonometer at a heart rate level that does not exceed an anaerobic metabolism of approx.120-130 Hr max.The training was conducted on the basis of our own experience based on clinical work.Each patient was treated individually under the supervision of a therapist through a one-on-one method.The duration of the entire training session is 60 min of resistance exercises, 15 min on a cycloergometer, and 10 min of breathing.Resistance exercises were performed simultaneously on both limbs.(Figure 2. Description of rehabilitation patients post COVID-19).The therapy was conducted by a qualified therapist under their constant supervision, at the same time and place, using the same device.Before and immediately after therapy, patients reported possible side effects and increased shortness of breath (above 1 on the mMRC scale).The exercises were based on the patient's subjective feelings (Table 2).The therapy was conducted by a qualified therapist under their constant supervision, at the same time and place, using the same device.Before and immediately after therapy, patients reported possible side effects and increased shortness of breath (above 1 on the mMRC scale).The exercises were based on the patient's subjective feelings (Table 2).Postural and baropodometric stability were assessed on the FreeMED Base tensometric platform by means of the dynamic, static, and postural control analysis based on a 1 min Romberg's test with eyes closed and open.The patients were examined by means of the same device, in the same ambient conditions, at the time of a day, and by the same person performing the measurements.The measurements were analysed by means of the Free Step software version 1.3.5.The dynamic analysis involved each of the individuals under analysis, who walked a specific and equal distance on the tensometric platform while the foot pressure was being measured.Within the framework of the dynamic analysis, the right and left foot parameters were compared, namely, foot trace length (mm), gait length line (mm), foot surface (mm 2 ), as well as the maximum and mean load (g/cm 2 ).On the other hand, the static analysis encompassed the measurement of the foot pressure for 5 s while standing in the upright position with upper limbs.The following parameters were analysed: foot surface (cm 2 ), foot load (%), and maximum and mean foot load (g/cm 2 ).The postural control assessment entailed the continual measurement of the centre of the foot pressure (COP), the displacement of which enables us to obtain the balance details.The following parameters were compared: swing length (mm), surface area (mm 2 ), speed (mm/s), and the length of the minimum and maximum swing of the patient's centre of gravity.The 6 min walk test entailed the pre-and post-test measurement of the following parameters: systolic and diastolic blood pressure, pulse, saturation, and dyspnoea in terms of the mMRC Scale.The results obtained before and after the rehabilitation were compared.The research did not include comparisons with a control group.Only post-COVID-19 patients were assessed.
All the variables under study were quantified or ordinal.They were compared within independent groups by means of the Wilcoxon signed-rank test.All of the computations were conducted by means of the IBM SPSS Statistics 27.0 software.The statistical hypotheses were tested in terms of the statistical significance p < 0.05.

Results
The dynamic analysis indicated improvement-the maximum and mean left foot load in gait decreased statistically significantly, but the right foot one increased statistically insignificantly.The results showed no change with respect to the trace length, foot surface, or gait line length (Table 3).The static analysis indicated a decrease in the foot surface, and as far as the statistical significance is concerned, the whole foot surface decreased, and the left back and forefoot pressure decreased, too.Furthermore, the maximum and mean right lower limb load increased in correspondence with the previously assumed statistical significance (Table 3).The outcome of the postural control assessment indicated the capacity for improvement in maintaining the centre of gravity as far as the foot support surface is concerned.Romberg's coefficients decreased with respect to the swings, ellipse surface, and mean speed with eyes open, and statistical significance was indicated with respect to the ellipse surface (Table 4).Saturation statistically significantly increased, and the pulse decreased throughout the course of the 6 min walk before effort.After the respiratory and physical capacity exercises, dyspnoea parameters improved in terms of the mMRC Scale-the majority of patients considered it to be at 1 and 0 after therapy.Similar results were delivered after the 6 min walk test.Pulse and dyspnoea decreased as a result of the therapy (Table 5).

Discussion
Post-COVID-19 syndrome constitutes a new clinical challenge that requires specific therapy involvement from the medical team for treatment and diagnosis purposes.SARS-CoV-2 infection symptoms may sustain for many months after a negative test or moderate course of the disease.The symptoms do not only refer to the lungs, which are most often affected in the first phase of the disease.Most of the time, the symptoms refer to the central and peripheral nervous system, manifesting themselves in peripheral neuropathy, headaches, dizziness, muscle pain, fatigue, memory loss, depression, or sleep disorders [10][11][12].According to the research outcomes, the diaphragm, as the main respiratory muscle, also plays a number of essential physiological functions through the sense of pain, supporting stomach-oesophagus function, and finally through posture stabilisation supported by the lumbar spine, by means of the abdominal pressure that it produces.That fact may matter in the case of the rehabilitation of post-COVID-19 patients [13].On the other hand, the balance assessment must be considered as the process integrating numerous stimuli, and the related notion of stability should be treated as the capability to regain balance and to lose it within the sphere that is controlled by means of many properly functioning systems, including the nervous and visual systems and the proper perception and integration of stimuli from the surrounding environment, for instance, proprioception.The analysis of the centre of the foot pressure is one of the sensitive balance assessment methods applied as an auxiliary statistical measure for postural control examination purposes [14].On the other hand, in order to assess the gait and the migrating centre of gravity pressure, baropodometric assessment methods are applied that most frequently depict the differences in the diagnostics of rheumatic disease and related dysfunctions and foot deformities [15][16][17].
A number of studies indicate that the balance disorders occur in the case of post COVID-19 patients [10,[17][18][19][20][21].The provisional outcome of examinations carried out within a group of individuals who recovered from COVID-19 infection as compared to the healthy individuals examined before the pandemic indicate that past infection affects the baropodometric as well as postural control parameters [6,7].Our study showed that patients coordinated actions aimed at balancing the centre of pressure during walking by loading the dominant side of the body (at the beginning of the study, all patients indicated that the right side of the body was dominant).This may suggest a benefit from breathing exercises as part of an assessment of balance-related postural control.A change in the foot surface, including the rear and forefoot, and the entire foot surface area may indicate an improvement in the efficiency of the foot muscles while maintaining the stability of the foot arch.After the therapy, the load on the lower limb changed-the load on the left foot decreased and the load on the right foot increased, which may indicate a beneficial effect of postural control on the movement of the centre of pressure to the benefit of the more efficient limb.The influence of the diaphragm, which is the main respiratory muscle and is activated during breathing exercises, on balance functions and postural stabilization was already confirmed in the works of Kocjan J. [13].
The study conducted by Leszczak J. et al. assessed the impact of rehabilitation in the case of patients who had recovered from a brain stroke or a brain stroke with concurrent COVID-19 infection to the extent of mobility and balance.The study was conducted by means of Time Up and Go testing as well as the Tinetti Test, confirming that hospital rehabilitation at an early stage after a brain stroke improved mobility and balance and mitigated the risk of falls amongst the patients after a brain stroke, both with the concurrent COVID-19 infection and without it [22].
Still, another study conducted by Paéz W. et al. was indicative of a significant improvement in quality of life and functional capacity as well as a reduction in mental and cognitive strain within an 8-week rehabilitation programme.The significant improvement was proven by a variety of physical capacity tests, including the 6 min walk test, 1 min sitting-rising test, dynamometry, the Tinetti Test, and the Berg Balance Test (p < 0.001) [23].Accordingly, that study also indicated an improvement in the physical capacity measured by means of the 6 min walk test-the saturation and pulse parameters before the test improved, and the pulse parameters after the test improved due to the therapy that had been applied.
There are no relevant reports on the assessment of baropodometric parameters to the extent of foot pressure amongst post-COVID-19 patients after rehabilitation.However, researchers undertook the assessment of gait and respiratory function in the case of a patient who had undergone a severe COVID-19 course by means of a robot workout.The patienta 48-year-old woman who had undergone a severe COVID-19 course-was subject to the 6-week hospital rehabilitation programme.The patient showed persisting lung function and physical capacity impairment, including gait and balance control disorders.After the training workout, the maximum inspiratory pressure and maximum exhalation pressure improved, the gait pace accelerated, and the balance control improved, too.As far as the physical efficiency was concerned, the distance covered during the 6 min walk test lengthened with concurrent pulse and saturation improvement [24].The aforementioned study is indicative of similar results to those shown here.
An improvement in the result of the 6 min walk test was also achieved under the study conducted by Nopp S. et al.Patients improved their test results by 62.9 m (±48.2, p < 0.001) on average; moreover, a significant improvement was delivered with respect to dyspnoea (p < 0.001), fatigue (p < 0.001) and quality of life (p < 0.001).The lung function parameters (the expiratory volume per 1s, the lung diffusion capacity, and the inspiratory pressure increased) improved throughout the rehabilitation course.This result allows us plausibly to state that in patients who underwent a severe COVID-19 course, their physical efficiency, functional condition, dyspnoea, fatigue, and quality of life improved after 6 weeks of the personalised interdisciplinary respiratory rehabilitation workout programme [25].In our study, the patients also achieved a better physical capacity after outpatient rehabilitation including respiratory rehabilitation.
The pandemic period contributed to the occurrence of many functional disorders throughout the body.
Restrictive measures against the effects of COVID-19 taken by the governments of many countries were aimed at eliminating the spread of the pandemic, which resulted in a reduction in the number of people suffering from otitis media, which is confirmed by the work of G. Iannella and co-authors [26].This is why comprehensive preventive measures, including systemic rehabilitation, are so important.

Conclusions
Physical and respiratory capacity rehabilitation was very much beneficial for patients who underwent SARS-CoV-2 infection in terms of saturation, pulse, and dyspnoea.
Notwithstanding the lack of a training workout focusing on balance control, gait, and postural stability, a positive impact was provisionally confirmed to the extent of gait and balance control amongst post-COVID-19 patients who had undergone physical capacity and respiratory rehabilitation-an amazing effect was observed on the centre of gravity migration function while walking, and foot arch shape was achieved as a result of respiratory and physical capacity therapy, notwithstanding the lack of exercises focusing on foot muscle functional capacity.
These results may confirm a key role of the diaphragm as a stabiliser muscle contributing to static and dynamic function-gait-requiring further research.
Limitations, Recommendations, and Generalizations: The study conducted had both limitations and benefits.Limitations include the fact that the results of posturgraphic and functional tests may be influenced by the patient's resting state or mood, which may reduce test values.Future studies should consider including an additional survey assessing the patient's mood and wakefulness.Additionally, patients' levels of physical activity may also impact their ability to maintain balance, which should be considered in further research.The presented posturographic and clinical assessment can be used both in the
ventilation, endurance training was performed on a cycloergonometer at a heart rate level that does not exceed an anaerobic metabolism of approx.120-130 Hr max.The training was conducted on the basis of our own experience based on clinical work.Each patient was treated individually under the supervision of a therapist through a one-on-one method.The duration of the entire training session is 60 min of resistance exercises, 15 min on a cycloergometer, and 10 min of breathing.Resistance exercises were performed simultaneously on both limbs.(Figure 2. Description of rehabilitation patients post COVID-19).

Table 2 .
Descriptors for resistance training interventions.

Table 2 .
Descriptors for resistance training interventions.

Table 3 .
Dynamic and static analysis of the patients before and after the therapy.

Table 4 .
Analysis of the patients' postural control parameters before and after the therapy.

Table 5 .
Comparison of the effect before and after the therapy with respect to dyspnoea in terms of mMRC Scale, saturation, systolic pressure, diastolic pressure, and pulse before and after the 6 min walk test [own source].