Temperature-dependent Changes in Cardiovascular Parameters During Warm Water Footbaths in Healthy Women

Study Overview
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Brief Summary
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A study to explore whether different temperatures of warm water footbaths have different effects on the cardiovascular system, the autonomic nervous system and the general well-being of healthy women.

Detailed Description
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This is a blinded, four-arm randomized controlled trial with crossover design to explore the effects of warm water footbaths with different water temperatures on cardiovascular stress, reaction of the autonomic nervous system and a feeling of comfort and warmth in healthy female volunteers. Cardiovascular and ANS measurements are performed continuously throughout the interventions and the participants rate their feelings of warmth, general well-being and the footbath-related comfort with questionnaires.

Official Title
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Temperature-dependent Changes in Cardiovascular Parameters During Warm Water Footbaths in Healthy Female Volunteers - a Blinded, Randomized, Controlled, Four-arm Study With Cross-over Design

Conditions
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Warm Footbath, Cardiovascular System, Autonomic Nervous System

Intervention / Treatment
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* Other: 38°C warm water footbath
* Other: 40°C warm water footbath
* Other: 42°C warm water footbath
* Other: 38-42°C rising temperature footbath


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Written informed consent Age between 18 and 55 years Exclusion Criteria: Male sex Chronic skin lesions at the lower legs or feet Varicose veins grade 3 and grade 4 (Marshall stage classification), chronic venous insufficiency Cardiac arrhythmia Cardiac pacemaker Asthma bronchiale Consumption of HRV-modulating medication (especially tricyclic antidepressants, beta blockers) Pregnancy Insufficient knowledge of the German language

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 55 Years

Sexes Eligible for Study
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Female

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: 38° C footbath<br>Footbath with warm water at a constant temperature of 38° C | Other: 38°C warm water footbath<br>* A ten-minute pre-intervention rest period followed by a 30-minute footbath with 16 l of warm water at a constant temperature of 38°C, followed by a ten-minute post-intervention rest period.<br>|
| Experimental: 40° C footbath<br>Footbath with warm water at a constant temperature of 40° C | Other: 40°C warm water footbath<br>* A ten-minute pre-intervention rest period followed by a 30-minute footbath with 16 l of warm water at a constant temperature of 40°C, followed by a ten-minute post-intervention rest period.<br>|
| Experimental: 42° C footbath<br>Footbath with warm water at a constant temperature of 42° C | Other: 42°C warm water footbath<br>* A ten-minute pre-intervention rest period followed by a 30-minute footbath with 16 l of warm water at a constant temperature of 42°C, followed by a ten-minute post-intervention rest period.<br>|
| Experimental: Rising temperature footbath<br>Footbath with warm water rising from 38° C to 42° C | Other: 38-42°C rising temperature footbath<br>* A ten-minute pre-intervention rest period followed by a 30-minute footbath with 16 l of warm water. Water temperature starts at 38°C and is increased by 1°C every 6 minutes, resulting in 42°C after 30 minutes. The footbath is followed by a ten-minute post-intervention rest period.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Pressure Rate Product (PRP) at timepoint t5 (footbath minute 21-30) | Pressure Rate Product (PRP), calculated from systolic blood pressure (measured with the Mobil-O-Graph® PWA) and heart rate (measured with the Bittium Faros 360TM ECG recorder) at timepoint 5 (t5 = mean of the measurements recorded from minute 21 to minute 30 of the footbath). | Timepoint 5 (t5 = mean of the measurements recorded from minute 21-30 of the 30-minute footbath) | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in Pressure Rate Product (PRP) at timepoints t1 (minute 1-10 of the pre-intervention rest period), t3 (minute 1-10 of the footbath), t4 (minute 11-20 of the footbath), and t7 (minute 1-10 of the post-intervention rest period). | Pressure Rate Product (PRP), calculated from systolic blood pressure (measured with the Mobil-O-Graph® PWA) and heart rate (measured with the Bittium Faros 360TM ECG recorder) at timepoints t1 (t1 = mean of the measurements recorded from minute 1 to minute 10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1 to minute 10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11 to minute 20 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1 to minute 10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Heart rate variability (HRV) analysis: Change in SDNN | SDNN: Standard deviation of normal to normal (NN) intervals (ms) (Bittium Faros 360TM ECG recorder). Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in pNN50 | pNN50: Percentage of successive NN intervals that differ from each other by more than 50 ms (%) (Bittium Faros 360TM ECG recorder). Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in HF | HF: High frequency power band (0.15-0.40 Hz) (ms2) from frequency domain analysis (Bittium Faros 360TM ECG recorder). Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in LF | LF: Low frequency power band (0.04-0.15 Hz) (ms2) from frequency domain analysis (Bittium Faros 360TM ECG recorder). Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in LF/HF ratio | LF/HF ratio = ratio of two bands from frequency domain analysis: LF band (0.04-0.15 Hz), HF band (0.15-0.40 Hz) (Bittium Faros 360TM ECG recorder). Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in VLF | VLF: Very low frequency power band (0.0033-0.04 Hz) (ms2) from frequency domain analysis (Bittium Faros 360TM ECG recorder). Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in Mean Heart Rate | Mean heart rate (bpm) (Bittium Faros 360TM ECG recorder). Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in SD2/SD1 ratio | SD2/SD1 ratio, derived from Poincaré plot (Bittium Faros 360TM ECG recorder). Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in Stress Index | Stress Index (SI) according to Baevsky's formula SI = AMo/2Mo*MxDMn (Mo = mode, AMo = mode amplitude, MxDMn = variation range of RR intervals) (Bittium Faros 360TM ECG recorder). Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in Respiration Rate | Respiration rate (1/min) (Bittium Faros 360TM ECG recorder). Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in Heart Rate/Respiration Rate ratio | Heart rate/respiration rate ratio (Bittium Faros 360TM ECG recorder). Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in RMSSD | RMSSD: Root mean square of successive differences (ms) (Bittium Faros 360TM ECG recorder). Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in Stiffness Index | Stiffness Index, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in Perfusion Index | Perfusion Index, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in Peak to Peak Time | Peak to Peak Time (PPT, ms), measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in SlopeInW1 | SlopeInW1, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in SlopeInW2 | SlopeInW2, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in SlopeInW3 | SlopeInW3, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in SlopeInW4 | SlopeInW4, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in Reflection Index | Reflection Index, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in TimeTX | TimeTX (ms), measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in TimeTY | TimeTY (ms), measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in QuotTYTX | QuotTYTX, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in AreaAX | AreaAX, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in AreaAY | AreaAY, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in QuotAYAX | QuotAYAX, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in TimeTV | TimeTV (ms), measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in TimeTW | TimeTW (ms), measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in QuotTVTW | QuotTVTW, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in AreaAV | AreaAV, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in AreaAW | AreaAW, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in QuotAVAW | QuotAVAW, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in Oxygen Saturation | Oxygen saturation (SpO2, %), measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in Pulse Transit Time | Pulse Transit Time (PTT, ms), measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in Systolic Blood Pressure | Systolic Blood Pressure (mmHg), measured with the Mobil-O-Graph® PWA. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in Diastolic Blood Pressure | Diastolic Blood Pressure (mmHg), measured with the Mobil-O-Graph® PWA. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in Mean Arterial Pressure | Mean Arterial Pressure (mmHg), measured with the Mobil-O-Graph® PWA. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in Pulse Pressure | Pulse Pressure (mmHg), measured with the Mobil-O-Graph® PWA. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in Stroke Volume | Stroke Volume (ml), measured with the Mobil-O-Graph® PWA. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in Cardiac Output | Cardiac Output (l/min), measured with the Mobil-O-Graph® PWA. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in Peripheral Resistance | Peripheral Resistance, measured with the Mobil-O-Graph® PWA. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in Cardiac Index | Cardiac Index, measured with the Mobil-O-Graph® PWA. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in Augmentation Pressure | Augmentation Pressure (mmHg), measured with the Mobil-O-Graph® PWA. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in Augmentation Index | Augmentation Index, measured with the Mobil-O-Graph® PWA. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in Pulse Wave Velocity | Pulse Wave Velocity (PWV, m/s), measured with the Mobil-O-Graph® PWA. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period). | Physiological parameters are measured continuously (Vitaguard® VG 3100, GETEMED; Bittium Faros 360TM) and every 2 min (Mobil-O-Graph® PWA) for a total duration of 50 min. | 
| Change in warmth perception at the feet | Self-reported warmth perception at both feet, assessed with the Herdecke warmth perception questionnaire immediately before (timepoint 2, t2), immediately after (timepoint 6, t6) and 10 minutes following the footbath (timepoint 8, t8). Each item is scored 0-4 (0 = cold; 4 = hot), yielding a mean between 0 and 4. | Immediately before (timepoint 2, t2), immediately after (timepoint 6, t6) and 10 minutes following the footbath (timepoint 8, t8) (length of footbath is up to 30 minutes). | 
| Change in warmth perception at the hands | Self-reported warmth perception at both hands, assessed with the Herdecke warmth perception questionnaire immediately before (timepoint 2, t2), immediately after (timepoint 6, t6) and 10 minutes following the footbath (timepoint 8, t8). Each item is scored 0-4 (0 = cold; 4 = hot), yielding a mean between 0 and 4. | Immediately before (timepoint 2, t2), immediately after (timepoint 6, t6) and 10 minutes following the footbath (timepoint 8, t8) (length of footbath is up to 30 minutes). | 
| Change in warmth perception at the head | Self-reported warmth perception at the head, assessed with the Herdecke warmth perception questionnaire immediately before (timepoint 2, t2), immediately after (timepoint 6, t6) and 10 minutes following the footbath (timepoint 8, t8). Each item is scored 0-4 (0 = cold; 4 = hot), yielding a mean between 0 and 4. | Immediately before (timepoint 2, t2), immediately after (timepoint 6, t6) and 10 minutes following the footbath (timepoint 8, t8) (length of footbath is up to 30 minutes). | 
| Change in overall warmth perception | Self-reported overall warmth perception, assessed with the Herdecke warmth perception questionnaire immediately before (timepoint 2, t2), immediately after (timepoint 6, t6) and 10 minutes following the footbath (timepoint 8, t8). The item is scored 0-4 (0 = cold; 4 = hot). | Immediately before (timepoint 2, t2), immediately after (timepoint 6, t6) and 10 minutes following the footbath (timepoint 8, t8) (length of footbath is up to 30 minutes). | 
| Change in general well-being | Self-reported well-being, assessed with the Basler Befindlichkeits-Skala (Basel Mood Questionnaire, BBS) immediately before (t2), immediately after (t6) and 10 minutes following the footbath (t8) (BBS: 16 items; 7-point rating scale; higher values represent a better outcome). | Immediately before (timepoint 2, t2), immediately after (timepoint 6, t6) and 10 minutes following the footbath (timepoint 8, t8) (length of footbath is up to 30 minutes). | 
| Change in feeling of comfort during footbath | Self-reported footbath comfort, assessed with a 7-point face scale ranging from very comfortable (laughing face) to very hard stress (crying face). | Immediately before the footbath (timepoint 2, t2), every 6 minutes during the 30-minute footbath, and 10 minutes following the footbath (timepoint 8, t8). | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Warm water footbath, Temperature-dependent effects, Cardiovascular System, Autonomic Nervous System, Heart Rate Variability, Healthy female volunteers