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

Autonomic Nervous System Clinical Trial

Official title:

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

Clinical Trial Details — Status: Completed

Administrative data

• NCT number: NCT04579497
• Other study ID #: SWI_16
• Status: Completed
• Phase: N/A
• Start date: October 26, 2020
• Est. completion date: May 31, 2021

Study information

• Verified date: July 2021
• Source: ARCIM Institute Academic Research in Complementary and Integrative Medicine
• Contact: n/a
• Is FDA regulated: No
• Study type: Interventional

Clinical Trial Summary

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.

Description:

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.

Recruitment information / eligibility

• Status: Completed
• Enrollment: 28
• Est. completion date: May 31, 2021
• Est. primary completion date: May 31, 2021
• Accepts healthy volunteers: Accepts Healthy Volunteers
• Gender: Female
• Age group: 18 Years to 55 Years

Eligibility

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

Related Conditions & MeSH terms

• Autonomic Nervous System
• Cardiovascular System
• Warm Footbath

Intervention

Other:
• 38°C warm water footbath
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.
• 40°C warm water footbath
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.
• 42°C warm water footbath
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.
• 38-42°C rising temperature footbath
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.

Locations

Country	Name	City	State
Germany	Arcim Institute	Filderstadt	Baden-Württemberg

Sponsors (2)

Lead Sponsor	Collaborator
ARCIM Institute Academic Research in Complementary and Integrative Medicine	Universität Tübingen

Country where clinical trial is conducted

Germany, 

Outcome

Type	Measure	Description	Time frame	Safety issue
Other	Change in warmth perception and skin stimulus at the feet during the footbath	Self-reported perception of warmth and skin stimulus during the footbath, assessed with a dynamic warmth and skin stimulus visual analog scale (VAS), applied once per minute (0 = cold/no stimulus; 10 = very hot/very strong stimulus).	Up to 30 minutes.
Other	Preferred footbath	Self-reported personal preference of footbath, assessed with a short questionnaire asking which footbath had the most positive overall effect (check boxes to mark for the first, second, third, or fourth footbath) and why (short, self-formulated statement of reasons). Assessed once after the fourth footbath intervention.	10 minutes.
Primary	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	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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.
Secondary	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).
Secondary	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).
Secondary	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).
Secondary	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).
Secondary	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).
Secondary	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).