High levels of stress cause serious health problems and reduce the quality of life. There is a lack of research proving the use of natural resources for the treatment or prevention of the stress and recovery from post Covid-19 condition. The goal of research: to assess the impact of natural resources (geothermal/mineral water, mud, salt, climate) on reducing stress and improving stress-related mental and physical health, as well as the safety of the procedures. The study will be randomized, controlled, parallel group, single- blinded (to researchers). The complex of procedures of water pool, mineral water bath, mud wrapping, salt therapy, nature therapy procedure will be provided with the different duration and mode (inpatient, outpatient). Primary outcomes- the effect on stress level; secondary outcomes: the effects on stress-related mental and physical health, work and social adaptation, tolerance and safety of balneotherapy procedures. The observation: before, after treatment, after 3 and 6 month of follow-up will be reveled.

The burden of stress and the consequences of Covid-19 pandemia complicates the existing capacities of the health care system and harms the efficiency and economy, therefore effective strategies are needed to reduce the consequences by creating science-based methodologies to strengthen and restore health in resorts, which would encourage wellness services, using the unique natural resources available in Lithuanian resorts and resort areas, development and would allow to compete with the most advanced European health and rehabilitation centers.

Objectives of biomedical research:

1. To assess the effectiveness of Lithuania's unique natural resources in reducing stress and improving stress-related mental and physical conditions.
2. After identifying the group of those who have recovered from Covid-19, evaluate the effectiveness of natural factors for improving this condition.
3. To present methodological recommendations for the use of Lithuania's natural resources.

Hypotheses of biomedical research:

1. It is likely that a complex of procedures using natural resources will reduce stress, anxiety, and depression.
2. It is likely that procedures with nature factors improve work and social adaptation.
3. The effect of natural resource therapy is effective regardless of the duration of treatment and season.

A multicenter, prospective, randomized controlled, single-blinded parallel group scientific study will be made.

Participants: 330 participants experiencing increased and poorly controlled stress or reduced sense of well-being in Klaipėda and Druskininkai territories (6 groups of 55 people each). Sampling is a probabilistic nest (cluster), in which each research participant's entry into the sample is multi-stage, criterion-referenced. The sample size required for statistically significant comparisons of the rehabilitation effect of the means of quantitative variables before and after the procedures was calculated by the G*Power program.

• The subject will be randomly assigned to the respective group (I-VI) by a computer program after the initial examination (T0) at the study centers. Grouping will be done by a statistician.
• • coding/blinding (if applicable, a description is provided so that no one (subjects, researchers, statisticians, etc.) will know which group the subject belongs to),
• After the initial screening, the completed questionnaires will be modally coded by a statistician. The researchers conducting the clinical trial will not know which group the subject belongs to.

Group I will be given a complex of balneological procedures: swimming pool 20 min, 34-36° mineral/geothermal water procedure 20 min, sapropel wrapping 20 min, salt therapy 25 min. Duration of treatment - 6 days.

Group II will be given a complex of balneological procedures as group I. Duration of treatment - 11 days. Comparing the results of groups I and II will allow us to assess the influence of treatment duration.

Group III will be given a complex of balneological procedures like groups I and II and a natural therapy procedure developed by the researchers: a 45-minute walk in nature (forest, seaside), a complex of simple strength and breathing low-intensity exercises, sensory impulses (landscape , forest smells - aromatherapy, natural sounds of nature, collecting nature's goodies (berries, pine cones, leaves, etc.), awareness therapy, heliotherapy.Duration - 11 days. Comparison of groups I and II will allow to evaluate the influence of complex treatment, including nature therapy.

Group IV will be accommodated in the research center and will receive balneological treatments (as groups I and II). Duration of treatment 11 days. Comparison of the effect between groups I, II, III and IV will allow to assess the impact of inpatient rehabilitation treatment relatively.

Group V will be given only the natural therapy procedure (as in group III). Duration 11 days The results will make it possible to evaluate the benefits of the natural therapy procedure, which can be applied by the person himself to improve or restore health. Comparison with the results of group II will allow to evaluate the benefits of treatment with balneotherapy procedures in the institution.

Group VI - the control group, the participants of which will not be given any procedures. Duration 11 days Comparison with groups II, IV, V will allow us to evaluate the differences in the health effects of rehabilitation procedures and natural therapy compared to no treatment.

During the study, the sociodemographic, clinical, health, body condition and safety assessment data of the study participants will be collected. Data will be collected based only on the information provided by the participant and the results obtained during the study. The screening questionnaire will ask for gender, age, marital status, education, place of residence, nature of work, length of service and earnings, information on the occurrence of Covid-19 and the incidence of chronic diseases, lifestyle habits, the level of stress experienced and methods of management, the sense of well-being experienced and information , which is important when including in the study - the current exacerbation of a chronic disease; morbidity from an oncological or infectious disease, severe form of cardiovascular, nervous, mental, kidney disease or bleeding, recent surgery or major trauma, limitation of movement function; possible pregnancy or breastfeeding; Intolerance of balneotherapy treatment or thermal procedures applied during the 3-month period and plans to leave in the next 6 months, which would not ensure your participation in the entire study period.

During the study, objective measurements will be performed to determine the response of various body systems: BP (blood pressure), HR (heart rate), SpO2 (pulsoxymetry), spirometry, toe-to-floor distance, sit-to-reach test, dynamometry, body composition analysis, waist circumference, salivary cortisol, cognitive test set (alertness, working memory, spatial number search, logical reasoning). The results of the scales will be used to evaluate the results of the study: for stress - the perceived stress scale (PSS) and the General Distress Symptoms Scale (GSDS), for anxiety - the Anxiety and Restlessness Inventory (STAI), for depression - the Center for Epidemiological Research Revised Depression Scale (CESD-R-20), for fatigue - Multidimensional Fatigue Inventory (FAS), for sleep - one-point sleep quality scale (SQS), for adaptation - Work and Social Adaptation Scale (WSAS), for well-being - Arizona Integrative Outcomes Scale (AIOS), for general health and well-being - health questionnaire, procedures security assessment questionnaire.

Inclusion Criteria:

• Age 18- 65 years
• Strength of stress >3 (0 no stress - 10 unbearable stress, VAS) AND/OR
• Stress control <7 (0- I can't control - 10- I control perfectly, VAS)

Exclusion Criteria:

• Uncontrolled/decompensated systemic diseases (hematological, endocrine, rheumatological, renal, cardiovascular, digestive, pulmonary),
• Active infection,
• Malignant tumors,
• Surgery or major trauma in the past year,
• Impaired ability to walk,
• Applied balneotherapy treatment during a 3-month period,
• Pregnancy/lactation,
• Bleeding,
• Severe mental disorder.

Sharing of participant data is possible by separate agreement, only for scientific purposes in the relevant field.

The subject will be randomly assigned to the study group (I-VI) by a computer program after the initial examination (T0) at the study centers. Grouping will be done by a statistician. Coding/blinding will be done so that researchers, statisticians, etc. will not know which group the subject belongs to. After the initial screening, the completed questionnaires will be modally coded by a statistician. The researchers conducting the clinical trial will not know which group the subject belongs to.