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.