The Impact of Complex Rehabilitation Treatment on Sarcopenia—Pathology with an Endocrine Morphological Substrate and Musculoskeletal Implications

The pathogenesis of sarcopenia is multifactorial, including changes in the endocrine system. Easy-to-perform screening tests can guide the diagnosis of sarcopenia and the rehabilitation therapeutic conduct, which can act on many physiopathological links. This study was conducted over a period of 5 months, from April to August 2022, and included 84 patients hospitalized for a period of 10 days in the Balneal and Rehabilitation Sanatorium Techirghiol for complex physiotherapy, which included balneotherapy. In dynamics, both at admission and discharge, specific screening tests for sarcopenia (SARC-F questionnaire, grip strength, testing muscle strength at the level of the quadriceps, sit-to-stand tests (the time required for five consecutive rises and the number of rises performed in 30 s)) and the Visual Analogue Scale (VAS) for pain were performed. The study was conducted according to the norms of deontology and medical ethics. Results: A significant proportion of patients had a positive result in at least one of the tests for the screening of sarcopenia syndrome. The most eloquent results were obtained from the statistical analysis of the following parameters evaluated at admission: the SARC-F questionnaire and the sit-to-stand test—the number of rises in 30 s. In terms of dynamics, after performing the complex rehabilitation treatment, the patients recorded improvements in the established screening tests and improvements in pain symptoms evaluated with the help of the VAS. Conclusions: Sarcopenia, a pathology developed with aging, is frequently encountered among adults. In the future, it is important to perform screening for sarcopenia in both endocrinology and medical rehabilitation clinics. Good management of sarcopenia can influence therapeutic conduct and can prevent complications, improving the functional capacity and the quality of life of the patients.


Introduction
The first hypothesis of the study is that sarcopenia is a frequent but underdiagnosed pathology among adults and the elderly, which is why performing scientifically validated screening tests is very important. The second study hypothesis supports the endocrine manifestations of sarcopenia are frequently masked by the multiple comorbidities that elderly patients may have [13,15].
The main objectives of this study were to demonstrate the importance of screening tests and to evaluate the impact of multimodal rehabilitation treatment on patients with sarcopenia, a pathology with an endocrine morphological substrate.

Study Design
This was a prospective, longitudinal, before-after study conducted over a period of 5 months, from April to August 2022, in a representative unit in the field of medical rehabilitation in Romania.

Subjects
The study included 84 patients, aged between 50 and 79 years, hospitalized for 10 days in Techirghiol Balneal and Rehabilitation Sanatorium for balneary-physical-kinetic treatment.
The inclusion criteria for the patients were as follows: -Hospitalized in Balneal and Rehabilitation Sanatorium Techirghiol for musculoskeletal disorders; -Aged between 50 and 79 years; -Conscious, cooperative; - The possibility of performing all the pre-established screening tests.
The exclusion criteria for the patients were as follows: -Outpatient treatment for musculoskeletal disorders; -Age outside the selected range; -Uncooperative patients; -Comorbidities associated with the impossibility of performing all the pre-established screening tests.

Intervention
The patients were evaluated, by screening tests, in dynamics, both at admission and discharge to observe the impact of complex rehabilitation treatment on muscle mass, strength and function in the context of sarcopenia.
The rehabilitation treatment performed by the patients was standard, according to the existing treatment protocols at the level of the medical unit and the national and international balneological approach. The interventional treatment included 10 daily sessions of hydrokinetotherapy and hydrothermotherapy using specific natural environmental factors, namely sapropelic mud and salt water from Techirghiol Lake, as well as artificial physical agents such as electrotherapy, massage and of course exercise therapy.
The baths in the salty water of Lake Techirghiol (at 35 • C) and mud baths (at 38 • C) were alternated daily, for a period of 20 min. The hydrokinetotherapy was performed on the recommendation of the rehabilitation doctor and under the guidance and supervision of the rehabilitation assistant. At the recommendation of the rehabilitation doctor, each patient performed, depending on the associated musculoskeletal pathology, three electrotherapy procedures daily. Massage and exercise therapy were performed on the doctor's recommendation by the rehabilitation assistant, daily. For each patient included in the study, the same therapeutic objectives were respected to obtain a similar functional impact.

Measures
The SARC-F questionnaire, specific functional tests for sarcopenia and the Visual Analogue Scale were performed and analyzed. The study protocol is presented in Figure 1.

Measures
The SARC-F questionnaire, specific functional tests for sarcopenia and the Visual Analogue Scale were performed and analyzed. The study protocol is presented in Figure  1. The SARC-F questionnaire is a screening tool, easy to use in daily practice, made up of 5 questions (strength, walking assistance, lifting from a chair, climbing stairs, falling) [3]. Both at admission and at discharge, on day 1 and day 10, the patients completed the questionnaire and evaluated each question with 0-2 points. A score greater than or equal to 4 gives a positive result in the screening test performed with the help of this tool [3].
Other sarcopenia screening tools that evaluate muscle strength and performance are represented by grip strength (assessed with a dynamometer), testing muscle strength at the level of the quadriceps, sit-to-stand tests (the time required for five consecutive rises and the number of rises performed in 30 s).
Both at admission and at discharge, a subjective evaluation method that depends on the evaluator was used to evaluate quadriceps strength. On the first day and last day of hospitalization, the patient performed a calf extension while sitting, with the knee flexed at 90° and the leg outside the table, while the doctor put resistance on the lower third of the calf. This test was performed to assess if the patient had low muscle strength at this level.
The grip strength was evaluated with the help of a digital hand dynamometer at the level of the dominant hand both at admission (day 1) and at discharge (day 10). Suggestive values for sarcopenia depend on the sex of the patient. Positive screening for sarcopenia was considered <16 kg for women and <27 kg for men [7].
Sit-to-stand tests were performed both at admission (first day) and at discharge (last day). The patients were asked to stand up and sit on a chair with feet about shoulder width apart and the arms crossed at the wrist and held against the chest. The time taken to rise from the chair 5 times was recorded. A value greater than 15 s provided a positive screening for sarcopenia [7]. The second test consisted in counting the rises performed in 30 s. The positive screening depended on the patient s sex and age (Table 1).  The SARC-F questionnaire is a screening tool, easy to use in daily practice, made up of 5 questions (strength, walking assistance, lifting from a chair, climbing stairs, falling) [3]. Both at admission and at discharge, on day 1 and day 10, the patients completed the questionnaire and evaluated each question with 0-2 points. A score greater than or equal to 4 gives a positive result in the screening test performed with the help of this tool [3].
Other sarcopenia screening tools that evaluate muscle strength and performance are represented by grip strength (assessed with a dynamometer), testing muscle strength at the level of the quadriceps, sit-to-stand tests (the time required for five consecutive rises and the number of rises performed in 30 s).
Both at admission and at discharge, a subjective evaluation method that depends on the evaluator was used to evaluate quadriceps strength. On the first day and last day of hospitalization, the patient performed a calf extension while sitting, with the knee flexed at 90 • and the leg outside the table, while the doctor put resistance on the lower third of the calf. This test was performed to assess if the patient had low muscle strength at this level.
The grip strength was evaluated with the help of a digital hand dynamometer at the level of the dominant hand both at admission (day 1) and at discharge (day 10). Suggestive values for sarcopenia depend on the sex of the patient. Positive screening for sarcopenia was considered <16 kg for women and <27 kg for men [7].
Sit-to-stand tests were performed both at admission (first day) and at discharge (last day). The patients were asked to stand up and sit on a chair with feet about shoulder width apart and the arms crossed at the wrist and held against the chest. The time taken to rise from the chair 5 times was recorded. A value greater than 15 s provided a positive screening for sarcopenia [7]. The second test consisted in counting the rises performed in 30 s. The positive screening depended on the patient's sex and age (Table 1). In order to observe how many patients in the investigated group had a positive screening for sarcopenia, all five tests were performed.
The Visual Analogue Scale represents a subjective method for chronic and acute pain assessment [16]. This scale, which is easy and quick to perform, was applied to all the patients included in the study. To evaluate if the rehabilitation treatment improved the pain syndrome, patients were verbally asked by the clinician where the pain is on a scale from 0 (no pain) to 10 (worst pain imaginable), both at admission and at discharge.

Data Analysis
Each screening test performed at admission was analyzed as follows:

•
In relation to certain fixed parameters (sex, environment, age, weight status); • In relation to the Visual Analogue Scale (VAS) at admission/discharge; • In relation to the other screening tests performed at admission; • In relation to the result obtained in the same screening test at discharge (dynamic evaluation by performing a statistical association).
Statistical correlations were determined to identify the parameters of the screening tests that correlate best, as well as which screening test is more suggestive of sarcopenia.
The statistical analysis was performed using IBM SPSS statistics software version 23. The following tests were used in the statistical analysis of the obtained data: Wilcoxon signed-rank test and Z test for associations, chi-square test and Spearman's rank-order for correlations.
The study protocol was designed in accordance with the ethical guidelines of the Declaration of Human Rights and was approved by the Techirghiol Balneal and Rehabilitation Sanatorium Ethics Committee.

Results
Of the 84 analyzed patients, 61% were women, 82.1% were from urban areas, and 47.6% were aged between 50 and 59 years. It was found that 85.71% of the investigated patients were positive in at least one screening test performed for sarcopenia. Statistically significant associations and correlations were observed between the performed screening tests and between them and the rest of the evaluated parameters. The evaluation of the SARC-F questionnaire at discharge, after the complex rehabilitation treatment was performed, identified 13.10% of the total analyzed patients with a positive screening for sarcopenia. The association between SARC-F (total) at admission and discharge using the Wilcoxon signed-rank test and the Z test was statistically relevant (Figure 3). The evaluation of the SARC-F questionnaire at discharge, after the complex rehabilitation treatment was performed, identified 13.10% of the total analyzed patients with a positive screening for sarcopenia. The association between SARC-F (total) at admission and discharge using the Wilcoxon signed-rank test and the Z test was statistically relevant ( Figure 3). The evaluation of the SARC-F questionnaire at discharge, after the complex rehabilitation treatment was performed, identified 13.10% of the total analyzed patients with a positive screening for sarcopenia. The association between SARC-F (total) at admission and discharge using the Wilcoxon signed-rank test and the Z test was statistically relevant (Figure 3). The Wilcoxon signed-rank test determined that there was a statistically significant median decrease in SARC-F (total) score at admission (2.50) compared to SARC-F (total) score at discharge (1.00), Z = −5.456, p < 0.0001.  The Wilcoxon signed-rank test determined that there was a statistically significant median decrease in SARC-F (total) score at admission (2.50) compared to SARC-F (total) score at discharge (1.00), Z = −5.456, p < 0.0001.

Results Obtained According to Each Screening Test
(  The evaluation of muscle strength at the quadriceps level at discharge confirms that 30.95% of the total 84 patients registered a decrease in muscle strength. The association between quadriceps muscle strength at admission and discharge using the Wilcoxon signed-rank test and Z test has no statistical significance ( Figure 5).  The evaluation of muscle strength at the quadriceps level at discharge confirms that 30.95% of the total 84 patients registered a decrease in muscle strength. The association between quadriceps muscle strength at admission and discharge using the Wilcoxon signedrank test and Z test has no statistical significance ( Figure 5). The evaluation of muscle strength at the quadriceps level at discharge confirms that 30.95% of the total 84 patients registered a decrease in muscle strength. The association between quadriceps muscle strength at admission and discharge using the Wilcoxon signed-rank test and Z test has no statistical significance ( Figure 5). The Wilcoxon signed-rank test showed that at discharge, the treatment did not elicit a statistically significant change in testing muscle strength at the level of the quadriceps (Z = −1.633, p = 0.102). Indeed, the median score rating was the same at admission and at discharge.
(3) The evaluation of the grip strength at the level of the dominant hand was performed with the help of a dynamometer. It is observed that 14.29% of the patients registered values compatible with sarcopenia at admission ( Figure 6). The Wilcoxon signed-rank test showed that at discharge, the treatment did not elicit a statistically significant change in testing muscle strength at the level of the quadriceps (Z = −1.633, p = 0.102). Indeed, the median score rating was the same at admission and at discharge. At discharge, 11.9% of patients had a positive screening for sarcopenia through this evaluation method. The association of the grip strength at admission and at discharge using the Wilcoxon signed-rank test and the Z test was statistically significant (Figure 7). At discharge, 11.9% of patients had a positive screening for sarcopenia through this evaluation method. The association of the grip strength at admission and at discharge using the Wilcoxon signed-rank test and the Z test was statistically significant (Figure 7). At discharge, 11.9% of patients had a positive screening for sarcopenia through this evaluation method. The association of the grip strength at admission and at discharge using the Wilcoxon signed-rank test and the Z test was statistically significant (Figure 7). The Wilcoxon signed-rank test determined that there was a statistically significant median increase in grip strength (kg) at admission compared to grip strength (kg) at discharge, Z = −2.958, p < 0.0001.
(4) Performing the sit-to-stand test (the time required for five consecutive rises) recorded a positive screening for sarcopenia (>15 s) in 25% of patients ( Figure 8). The Wilcoxon signed-rank test determined that there was a statistically significant median increase in grip strength (kg) at admission compared to grip strength (kg) at discharge, Z = −2.958, p < 0.0001.
(4) Performing the sit-to-stand test (the time required for five consecutive rises) recorded a positive screening for sarcopenia (>15 s) in 25% of patients ( Figure 8). Performing the sit-to-stand test (the time required for five consecutive rises) at discharge recorded values for sarcopenia in 14% of cases. The association of this parameter at admission and at discharge using the Wilcoxon signed-rank test and Z test had statistical significance (Figure 9). admission and at discharge using the Wilcoxon signed-rank test and Z test had statistical significance ( Figure 9). Performing the sit-to-stand test (the time required for five consecutive rises) at discharge recorded values for sarcopenia in 14% of cases. The association of this parameter at admission and at discharge using the Wilcoxon signed-rank test and Z test had statistical significance (Figure 9). The Wilcoxon signed-rank test determined that there was a statistically significant median decrease in the time required for five consecutive rises at admission (12.65) compared to the time required for five consecutive rises at discharge (12.00), Z = −4.468, p < 0.0001.
(5) The interpretation of the results of the sit-to-stand test (the number of rises in 30 s) depends on the patient s sex and age (Table 1).
This test used as a screening method for sarcopenia was positive for 76.19% of the 84 evaluated patients (Figure 10). The Wilcoxon signed-rank test determined that there was a statistically significant median decrease in the time required for five consecutive rises at admission (12.65) compared to the time required for five consecutive rises at discharge (12.00), Z = −4.468, p < 0.0001.
(5) The interpretation of the results of the sit-to-stand test (the number of rises in 30 s) depends on the patient's sex and age (Table 1).
This test used as a screening method for sarcopenia was positive for 76.19% of the 84 evaluated patients (Figure 10). At discharge, 57.14% of patients had a positive screening for sarcopenia through the sit-to-stand test (the number of rises in 30 s). The association of this parameter at admission and at discharge using the Wilcoxon signed-rank test and Z test had statistical significance ( Figure 11). At discharge, 57.14% of patients had a positive screening for sarcopenia through the sit-to-stand test (the number of rises in 30 s). The association of this parameter at admission and at discharge using the Wilcoxon signed-rank test and Z test had statistical significance ( Figure 11). At discharge, 57.14% of patients had a positive screening for sarcopenia through the sit-to-stand test (the number of rises in 30 s). The association of this parameter at admission and at discharge using the Wilcoxon signed-rank test and Z test had statistical significance ( Figure 11). The Wilcoxon signed-rank test determined that there was a statistically significant median increase in the sit-to-stand test (the number of rises in 30 s) at admission (11.00) compared to the sit-to-stand test (the number of rises in 30 s) at discharge (12.00), Z = −5.405, p < 0.0001.

VAS Scores in Dynamics (Statistical Association)
The VAS scores obtained at admission and discharge were associated and evaluated using the Wilcoxon signed-rank test and the Z test. The results obtained showed that the algo-dysfunctional syndrome evaluated with the help of the Visual Analogue Scale (VAS), present at admission, improved during hospitalization, with significant relief of the pain ( Figure 12). The Wilcoxon signed-rank test determined that there was a statistically significant median increase in the sit-to-stand test (the number of rises in 30 s) at admission (11.00) compared to the sit-to-stand test (the number of rises in 30 s) at discharge (12.00), Z = −5.405, p < 0.0001.

VAS Scores in Dynamics (Statistical Association)
The VAS scores obtained at admission and discharge were associated and evaluated using the Wilcoxon signed-rank test and the Z test. The results obtained showed that the algo-dysfunctional syndrome evaluated with the help of the Visual Analogue Scale (VAS), present at admission, improved during hospitalization, with significant relief of the pain ( Figure 12). The Wilcoxon signed-rank test determined that there was a statistically significant median decrease in VAS score at admission (7.00) compared to VAS score at discharge (3.00), Z = −7.960, p < 0.0001.

Relevant Statistical Correlations Identified between the Associated Parameters
(1) By performing chi-square tests, it was observed that there was a statistically significant association between sex and grip strength (kg) at admission (p = 0.000 < 0.05), sex and the sit-to-stand test (the time required for five consecutive rises (seconds)) at admission (p = 0.011 < 0.05) and sex and the sit-to-stand test (the number of rises in 30 s) at admission (p = 0.016 < 0.05) (Tables 2-4).  The Wilcoxon signed-rank test determined that there was a statistically significant median decrease in VAS score at admission (7.00) compared to VAS score at discharge (3.00), Z = −7.960, p < 0.0001.

Relevant Statistical Correlations Identified between the Associated Parameters
(1) By performing chi-square tests, it was observed that there was a statistically significant association between sex and grip strength (kg) at admission (p = 0.000 < 0.05), sex and the sit-to-stand test (the time required for five consecutive rises (seconds)) at admission (p = 0.011 < 0.05) and sex and the sit-to-stand test (the number of rises in 30 s) at admission (p = 0.016 < 0.05) (Tables 2-4). (2) By performing chi-square tests, it was observed that there was a statistically significant association between age and quadriceps muscle strength at discharge (p = 0.024 < 0.05) and between age and the sit-to-stand test (the number of rises in 30 s) at discharge (p = 0.002 < 0.05) (Tables 5 and 6).
(3) By performing chi-square tests, relevant statistical correlations were identified between weight status and the sit-to-stand test (the number of rises in 30 s) at admission (p = 0.000 < 0.05).
(4) By performing chi-square tests and Spearman's rank-order correlation, relevant statistical correlations were identified between the SARC-F (total) and the other established tests of screening. Statistically significant associations were found between SARC-F (total) at admission and quadriceps muscle strength at admission (p = 0.002 < 0.05), SARC-F (total) at admission and grip strength (kg) at admission (p = 0.000 < 0.05), SARC-F (total) at admission and the sit-to-stand test (the time required for five consecutive rises (seconds)) at admission (p = 0.000 < 0.05) and SARC-F (total) at admission and the sit-to-stand test (the number of rises in 30 s) at admission (p = 0.013 < 0.05) (Tables 7-10).  A Spearman's rank-order correlation was run to determine the relationship between SARC-F (total) at admission and grip strength (kg) at admission/the sit-to-stand test (the time required for five consecutive rises (seconds)) at admission /the sit-to-stand test (the number of rises in 30 s) at admission.
There was a moderate, negative correlation between SARC-F (total) at admission and grip strength (kg) at admission, which was statistically significant (p < 0.001); a moderate, positive correlation between SARC-F (total) at admission and the sit-to-stand test (the time required for five consecutive rises (seconds)) at admission, which also was statistically significant (p < 0.001); and a moderate, negative correlation between SARC-F (total) at admission and the sit-to-stand test (the number of rises in 30 s) at admission, which also was statistically significant (p < 0.001) (Table 11). Table 11. Spearman's rank-order correlation between SARC-F (total) at admission and other parameters. There was a statistically significant association between SARC-F (total) at discharge and quadriceps muscle strength at discharge (p = 0.002 < 0.05), SARC-F (total) at discharge and grip strength (kg) at discharge (p = 0.001 < 0.05), SARC-F (total) at discharge and the sit-to-stand test (the time required for five consecutive rises (seconds)) at discharge (p = 0.000 < 0.05) and between SARC-F (total) at discharge and the sit-to-stand test (the number of rises in 30 s) at discharge (p = 0.001 < 0.05) (Tables 12-15). A Spearman's rank-order correlation was run to determine the relationship between SARC-F (total) at discharge and grip strength (kg) at discharge/the sit-to-stand test (the time required for five consecutive rises (seconds)) at discharge/the sit-to-stand test (the number of rises in 30 s) at discharge.
There was a moderate, negative correlation between SARC-F (total) at discharge and grip strength (kg) at discharge, which was statistically significant (p < 0.001); a weak, positive correlation between SARC-F (total) at discharge and the sit-to-stand test (the time required for five consecutive rises (seconds)) at discharge, which also was statistically significant (p < 0.001); and a moderate, negative correlation between SARC-F (total) at discharge and the sit-to-stand test (the number of rises in 30 s) at discharge, which also was statistically significant (p < 0.001) ( Table 16).

Discussion
It is important to have a screening strategy that allows the detection of sarcopenia in the early stages because it is extremely difficult to regain the already lost skeletal muscle mass.
An ideal screening test must be useful, valid, reliable and also cost-effective. Screening strategies can be carried out through several tools, and it is necessary to identify which is the most effective way to detect sarcopenia and to choose some methods optimal for the prevention and treatment of this pathology [3].
The evaluation and diagnosis of sarcopenia can represent a new objective in defining the incidence and prevalence of this pathology, which is why it is necessary to establish a solid and comprehensive algorithm. Refinement of the algorithm and its use in current practice can represent a tool for monitoring progress [4].
The results of the study demonstrated that our objectives were achieved, the screening tests proved their usefulness in identifying sarcopenia, and rehabilitation treatment can have an effect on sarcopenia through the possible effects on the endocrine system.
To our knowledge, this is the only study using balneotherapy for sarcopenic patients. Other studies which applied physiotherapy as a therapeutic intervention had good results for exercise therapy, while other methods were not largely studied [3,15,[17][18][19][20].
In this study, it was observed that although 85.71% of the patients were positive in at least one screening test, none were previously investigated for sarcopenia, and also none of them had a diagnosis of sarcopenia in their pathological history. A percentage of 27.38% of the evaluated patients had a positive screening for sarcopenia through the SARC-F questionnaire at admission. A percentage of 40.48% of the patients recorded decreases in the testing of muscle strength at the level of the quadriceps at admission. It is observed that 14.29% of the patients registered values compatible with sarcopenia in the evaluation of grip strength at the level of the dominant hand. The time required for five consecutive rises in the sit-to-stand test recorded a positive screening for sarcopenia for 25% of the patients. The number of rises in 30 s in the sit-to-stand test as a screening method for sarcopenia was positive for 76.19% of the evaluated patients.
The dynamic assessment of screening tests, both at admission and discharge, suggests that complex rehabilitation treatment can have an impact on sarcopenia. The decrease in the SARC-F (total) score at discharge indicates an improvement in functionality. This may be due to the decrease in the algo-functional syndrome and the increase in general muscle strength after performing the complex rehabilitation treatment. The testing of quadriceps muscle strength did not register considerable changes because this method is subjective and the improvements are difficult to quantify. The muscle strength measured with the dynamometer recorded a statistically significant increase. This method of evaluation uses a standard technique, devoid of subjectivity. The sit-to-stand tests (the time required for five consecutive rises and the number of rises in 30 s) were shortened at discharge, which indicates an increase in muscle strength and resistance following the complex treatment performed during hospitalization. These improvements can be due to both the hormonal implications (that complex rehabilitation treatment has through the use of natural therapeutic factors) and kinesiotherapy.
It was observed that evaluation of the Visual Analogue Scale (VAS) at discharge recorded improvements, with significant relief of the pain. Protocols that combine specific rehabilitation treatments with balneotherapy, including hydrotherapy, mud baths and exercise in hot thermal mud, could reduce pain and disability in patients identified as responders [21].
Relevant statistical correlations were identified between the associated parameters. The general muscle strength evaluated both at the level of the upper limbs and the lower limbs is related to sex. The endocrine system plays an important role, making the connection between the level of testosterone and estrogen in both sexes and the decline of muscle strength. There is a close relationship between age and muscle strength in the lower limbs. At discharge, the patients in the lower age ranges recorded improvements in the functional tests. This fact can be explained by hormonal status in relation to the patient's age. Most of the investigated patients have an increased body mass index. The obtained results support the concept of sarcopenic obesity from the literature [22][23][24][25][26]. Thus, the excess representation of adipose tissue can influence functionality.
It was found that the SARC-F questionnaire correlates, both at admission and discharge, with all other screening tests. Considering this, in daily practice, only the SARC-F questionnaire and the number of rises performed in 30 s in the sit-to-stand test can be used for the screening of sarcopenia.
The tests indicated for the diagnosis of sarcopenia can be performed for all cooperative, conscious patients who have multiple associated diseases. Likewise, rehabilitation treatments that use artificial and natural physical agents can be recommended to patients with kidney, liver or heart damage, without determining the side effects of drug treatments [7][8][9][10]13,20,21] The physical factors recommended in physical and rehabilitation medicine are considered environmentally friendly alternatives compared to drugs for the treatment of various pathologies [7,10].

Limitations of the Study
Because the screening does not always confirm the diagnosis and more advanced diagnostic methods are needed, no control group was established. The lack of a control group can be considered a limitation of the study, along with the high costs that advanced sarcopenia diagnostic methods can have. Another limitation of the study is that no studies were found in the literature about sarcopenia and complex rehabilitation treatment that includes balneotherapy, which could have an impact on the endocrine system.

Applications and Suggestions for Future Research
In the future, performing screening tests in endocrinology and medical rehabilitation clinics can guide the establishment of diagnosis and treatment of sarcopenia. Even though there have been efforts to standardize a blood test kit for sarcopenia, there is currently no such kit in use in clinical settings [18]. For future studies, a larger number of patients, a control group and more diagnostic methods will be used.

Conclusions
The interpretation of our findings demonstrates that the results of the study support the hypothesis, that the screening tests, which are easy to perform routinely, prove their usefulness in the diagnosis of sarcopenia and that multimodal rehabilitation treatment has an effect on sarcopenia, improving the results of the screening tests.
The link that sarcopenia creates between endocrinology and medical rehabilitation is based on the hormonal changes that balneal treatment with natural environmental factors and kinesiotherapy can induce. The screening tests-SARC-F questionnaire, grip strength (assessed with a dynamometer), testing muscle strength at the level of the quadriceps, and sit-to-stand tests (the time required for five consecutive rises and the number of rises performed in 30 s)-are easy to perform in a short time, are reliable and have minimal costs. The main parameters analyzed at admission with statistically significant results were the SARC-F questionnaire and the number of rises performed in 30 s in the sit-tostand test, which confirms the importance of screening by these methods in the evaluation of sarcopenia. Positive statistical variations following the therapeutic intervention were obtained for all the parameters included in the research, except the muscle strength at the level of the quadriceps, which underlines the importance of rehabilitation treatment in sarcopenia.
Screening can be easily performed in both endocrinology and medical rehabilitation clinics, and it can guide the conduct of diagnosis and treatment of sarcopenia (food supplements/hormonal supplements/increasing muscle strength with kinesiotherapy/balneal treatment with natural environmental factors). Sarcopenia has an endocrine morphological substrate with multiple functional implications. The approach to this pathology must be multidisciplinary. Informed Consent Statement: Informed consent was obtained from all subjects involved in the study.

Data Availability Statement:
The data presented in this study are available on valid request from the corresponding authors. The data are not publicly available due to privacy and ethical concerns.