This randomized controlled study evaluates the effects of cold water hydrotherapy as an adjunct to standard rehabilitation in patients with Post-COVID Syndrome. The primary aim is to assess changes in quality of life compared to standard rehabilitation alone.
Patients recovering from Post-COVID Syndrome often experience persistent fatigue, autonomic dysregulation, microcirculatory disturbances, and low-grade inflammation, all of which may hinder their return to full function. Kneipp hydrotherapy-using cold water applications-can address these pathophysiological changes through several mechanisms: Autonomic regulation: Cold stimuli trigger parasympathetic activation and improve sympathovagal balance, helping to stabilize heart rate variability and reduce symptoms of dysautonomia often seen in Post-COVID. Enhanced microcirculation: Repeated vasoconstriction and reactive vasodilation promote endothelial function and tissue perfusion, which may alleviate muscle aches, dizziness, and fatigue by improving oxygen and nutrient delivery. Anti-inflammatory effects: Hydrothermal stimuli have been shown to modulate cytokine profiles, increasing anti-inflammatory mediators and potentially dampening the persistent, low-grade inflammation implicated in Post-COVID pathophysiology. Musculoskeletal recovery: Thermo-mechanical stimulation relaxes tense muscle fibers, reduces pain perception, and supports gradual increases in physical capacity, all of which are important for overcoming Post-COVID deconditioning. Taken together, these effects suggest that adjunctive cold water hydrotherapy could accelerate functional recovery, reduce symptom burden, and enhance quality of life in Post-COVID rehabilitation. Baseline Assessments: At baseline, demographic data including sex, age, height, and weight will be collected. Participants will report their current main Post-COVID symptoms, which will be categorized into symptom clusters: Fatigue (A), Cognitive (B), and Somatic (C). Smoking history will be assessed, including smoking status (current, former, or never), number of cigarettes per day, years of smoking, and pack-years. The time (in months) since the COVID-19 infection that led to Post-COVID syndrome will be documented, along with the number of COVID-19 vaccinations received at the time of infection. Employment status will be recorded, distinguishing between full-time or part-time employment, COVID-related work disability, retirement, unemployment, or disability pension. Comorbidities will be documented across the following categories: cardiovascular, pulmonary, cerebrovascular, metabolic, musculoskeletal, psychiatric, and other conditions. The severity of the acute COVID-19 illness will be assessed using the WHO Clinical Progression Scale, including information on any hospital admission and length of stay (in days). Pulmonary function testing at baseline (V1) will include FEV₁, FVC, FEV₁/FVC ratio, and total lung capacity (TLC), all expressed as percent predicted. Autonomic function will be evaluated using the Schellong test. Vascular status will be assessed by four-limb blood pressure measurement. Additionally, self-reported work ability and the number of Post-COVID-related sick leave days within the past 12 weeks will be recorded.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
SINGLE
Enrollment
50
Cold water hydrotherapy (5-10 minutes each), twice daily during the 3-week multimodal inpatient rehabilitation program and once daily during the 6-month follow-up period
same rehabilitation program than the experimental group but without hydrotherapy
Schön Klinik Berchtesgadener Land
Schönau am Königssee, Bavaria, Germany
RECRUITINGHealth-related quality of life by Short Form-12 Health Survey (SF-12)
Change in the Short Form-12 physical and mental component summary scores
Time frame: From baseline (Visit 1) to end of inpatient rehabilitation (3 weeks, Visit 2)
Fatigue severity by Fatigue Severity Scale
Change in Fatigue Severity Scale score
Time frame: From baseline (Visit 1) to end of inpatient rehabilitation (3 weeks, Visit 2)
Sleep quality by Pittsburgh Sleep Quality Index
Change in Pittsburgh Sleep Quality Index score
Time frame: From baseline (Visit 1) to end of inpatient rehabilitation (3 weeks, Visit 2)
Health status by EuroQol-5 Dimensions-5 Levels
Change in EuroQol-5 Dimensions-5 Levels questionnaire score
Time frame: From baseline (Visit 1) to end of inpatient rehabilitation (3 weeks, Visit 2)
Autonomic function (heart rate variability by photoplethysmography)
Change in heart rate variability (root mean square of successive differences) measured by Kyto 2935 via photoplethysmography
Time frame: Daily during first 3 weeks of rehabilitation (Visit 1 to Visit 2)
Resting blood pressure (systolic and diastolic)
Change in morning resting systolic and diastolic blood pressure
Time frame: Daily during first 3 weeks of rehabilitation (Visit 1 to Visit 2)
Post-COVID work-absence days
Number of days of work absence due to Post-COVID-19 symptoms during the past 12-weeks
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Time frame: From baseline (Visit 1) to 3 months (Visit 3) and to 6 months (Visit 4)
Long-term quality of life by Short Form-12
Change in Short Form-12 scores at follow-up
Time frame: From baseline (Visit 1) to 3 months (Visit 3) and to 6 months (Visit 4)
Long-term fatigue by Fatigue Severity Scale
Change in Fatigue Severity Scale score at follow-up
Time frame: From baseline (Visit 1) to 3 months (Visit 3) and to 6 months (Visit 4)
Adherence to hydrotherapy
Proportion of prescribed hydrotherapy applications in the intervention group performed, as recorded in diary or app. Short-term Adherence: During the 3-week intervention phase, patients are considered "adherent" if they perform at least one hydrotherapy session per day on at least 75% of study days. We will compare health improvements between high-adherence and low-adherence participants. Long-term Adherence and Effects: Over the 3- and 6-month follow-up, "adherent" patients are those who continue self-administered hydrotherapy at least four times per week on at least 75% of follow-up weeks. We will assess whether these patients sustain greater gains in quality of life.
Time frame: During the 3-week intervention phase (up to Visit 2) and over the 6-month follow-up period (to Visit 4)
Adverse events recording
Number and severity of adverse events related to Kneipp hydrotherapy
Time frame: From start of intervention (Visit 1) through end of study (Visit 4, 6-month follow-up)
Long-term heart rate variability changes (HRV)
Change in heart rate variability parameters (root mean square of successive differences) measured by photoplethysmography. At follow-up visits patients will measure HRV for 7 consecutive days
Time frame: From baseline (Visit 1) to 3 months (Visit 3) and to 6 months (Visit 4)
Post-exertional malaise severity
Change in Post-Exertional Malaise score measured by the DePaul Symptom Questionnaire-Post-Exertional Malaise
Time frame: From baseline (Visit 1) to 6-month (Visit 4) follow-up
Daily well-being documentation
Self-reported daily well-being recorded via digital diary on a scale from 0 to 100
Time frame: Daily throughout the intervention and 6 months follow-up phase (Visit 1 to Visit 4)