Cold Water Exposure and Immune Function Study

Effects of a 4 Week Cold Tub vs Cold Shower Immersion Intervention on Immune Function, Sleep Quality, Mental Health and Well-being, Gut Health, and Muscular Strength in Healthy, Physically Active Adults

The purpose of this clinical trial is to explore the effects of a 4 week cold-water immersion (CWI) intervention on measures of immune function, sleep quality, mental health and well-being, and muscular strength. The main questions it aims to answer are:

• Does a 4 week CWI intervention improve measures of immune function, sleep quality, mental health and well-being, and muscular strength?
• Are there any differences in these measures when comparing cold tubs versus cold showers?

Researchers will compare chronic use of cold tubs to cold showers to see if cold water immersion may improve overall immune health and well-being. Participants will:

• Undergo 4 weeks of Cold Tub or Cold Shower interventions at a frequency of 3 times a week for 4 minutes, if placed in the CWI intervention groups
• Undergo testing measures at the two pre- and post- intervention time points, if placed in the healthy control group or the CWI intervention groups

Study Overview

• Status: Completed
• Conditions: Mental Health; Immune Function; Cold Water Immersion; Muscular Strength
• Intervention / Treatment: Other: Cold Water Immersion (CWI) - Cold Tub Immersion (CI); Other: Cold Water Immersion (CWI) - Cold Shower (CS); Other: Control Group (CO)

• Study Type: Interventional
• Enrollment (Actual): 37
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Colorado
    • Greeley, Colorado, United States, 80631
      • University of Northern Colorado - Gunter Hall

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Males and Females
• Aged 18-45

Exclusion Criteria:

• Currently practices CWI for [>3 times in the last month]
• Pregnant or planning to become pregnant
• Chronic use of anti-inflammatory medication
• Prior history of chronic disease conditions:
• Cardiovascular Disease
• Diabetes
• Cancer
• Raynaud's Disease
• Severe and untreated anxiety or depression

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Other
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Cold Tub Immersion Group (CI); Participants will utilize the research cold tub (10 ºC, 4-minutes, 3 times a week), following a standardized protocol (see intervention description).	Other: Cold Water Immersion (CWI) - Cold Tub Immersion (CI); Once thermoneutral procedures are complete, participants in the CI group will be seated in the cold tub and submerged into the water (10º C). The sternal notch of each participant will be used as the anatomical marker to mark submersion point. Participants will sit with both arms outstretched underwater with their backs not touching the sides of the tub. Participants with a shorter stature will be provided an underwater cushion to meet the submersion requirements. The 4-minute timer will begin once confirmation of the participants submersion level and posture is determined. Once completed, the participant will be instructed to slowly exit the tub and allowed to dry and change as necessary.
Experimental: Cold Shower Group (CS); Participants will utilize the research shower area (10 ºC, 4-minutes, 3 times a week), following a standardized protocol (see intervention description).	Other: Cold Water Immersion (CWI) - Cold Shower (CS); Once thermoneutral procedures are complete, participants in the CS group will be instructed to enter the research shower area. Within the shower area, the walls of the shower will be numbered from 1 to 4, with 1 defined as facing the faucet, 2 defined as 90° to the right of side 1, 3 defined as 180° from the faucet, and 4 defined as 270° to the right or 90° C to the left from side 1. Participants will be instructed to turn 90° to the right cycling through sides 1 to 4 and then back to 1 every 15 seconds prompted by the researcher. This will allow the participant to complete four full rotations in the shower during the 4-minute intervention time. The shower faucet is modified and oriented in a way where it only produces cold water (10º C) when turned on. Once completed, the participant will be instructed to slowly exit the shower and is allowed to dry and change as necessary
Other: Control Group (CO); Participants will not undergo any cold tub or cold shower intervention.	Other: Control Group (CO); Participants will be encouraged to maintain their current diet and exercise across the duration of the 4 week intervention. Participants will still be subjected to the pre- and post-intervention data collection session.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
C-Reactive Protein	Approximately 60mL of whole blood will be collected into serum separator tubes (Beckton Dickinson, East Rutherford, NJ, USA), allowed to clot for 30-min at room temperature, then centrifuged at 2000 RPM for 15 min. The serum will be pipetted into 1.5 mL microcentrifuge tubes (Eppendorf AG, Hamburg, Germany) and immediately stored in a -80 °C freezer. Serum concentrations of CRP will be determined with a commercially available enzyme-linked immunosorbent assay (ALPCO Diagnostics, Salem, NH, USA). Microplates will be read with an ELx800 BioTek microplate reader (BioTek Instruments, Inc., Winooski, VT, USA) at the recommended wavelength of 450 nanometers.	Visit 1A (Week 1) and Visit 2A (Week 4): 15 minutes for blood draw. The assay itself takes 3 hours.
Interleukin-6 (IL-6)	Approximately 60mL of whole blood will be collected into serum separator tubes (Beckton Dickinson, East Rutherford, NJ, USA), allowed to clot for 30-min at room temperature, then centrifuged at 2000 RPM for 15 min. The serum will be pipetted into 1.5 mL microcentrifuge tubes (Eppendorf AG, Hamburg, Germany) and immediately stored in a -80 °C freezer. Serum concentrations of IL-6 will be determined with a commercially available enzyme-linked immunosorbent assay (Thermo Fisher Scientific, Waltham, MA, USA). Microplates will be read with an ELx800 BioTek microplate reader (BioTek Instruments, Inc., Winooski, VT, USA) at the recommended wavelength of 450 nanometers.	Visit 1A (Week 1) and Visit 2A (Week 4): 15 minutes for blood draw. The assay itself takes 3 hours.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Pittsburgh Sleep Quality Index (PSQI)	Participants will be asked to complete a paper version of the Pittsburgh Sleep Quality Index (PSQI). The PSQI is a 19-question self-reported sleep quality tool broken up into 7 subcategories for scoring, such as subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medication, and daytime dysfunction. There are also 5 additional questions directed to the respondent's roommate or bed partner not used in the scoring, but utilized for clinical purposes.	Visit 1A (Week 1) and 2A (Week 4): 10 minutes each
Depression Anxiety and Stress Scales (DASS-21)	Participants will be asked to complete a paper version of the 21-item Depression Anxiety and Stress Scale (DASS-21). The DASS-21 consists of 21 questions using a 0-3 Likert scale assessing the participant's subjective mental health and stress state with a "0" indicating "Did not apply to me at all" and "3" indicating "Applied to me very much or most of the time." The DASS-21 contains 3 sub scales assessing Depression, Anxiety, and Stress consisting of 7 questions for each sub scale, where a high score of 28+ indicates "Extremely Severe" levels of Depression, a high score of 20+ indicates "Extremely Severe" levels of Anxiety, and a high score of 34+ indicates "Extremely Severe" levels of Stress, while low scores of 0-9 indicates "Normal" levels of Depression, scores of 0-7 indicates "Normal" levels of Anxiety, and scores of 0-14 indicates "Normal" levels of Stress.	Visit 1A (Week 1) and 2A (Week 4): 10 minutes each
Handgrip Dynamometry	Isometric grip strength will be measured by a Baseline 12-0286 Electronic Smedly Hand Dynamometer (Fabrication Enterprises, White Plains, NY). To begin the test, participants will stand upright in a relaxed position; their upper extremity peak isometric grip strength will be assessed with the shoulder in 180º of flexion, elbow at full extension, and wrist and forearm in a neutral position. When prompted, participants will squeeze the device with their dominant hand, delivering a maximal effort for 3-seconds, followed by relaxation. After 30-seconds, the test will be run again. Three sets are completed for this test, and the highest value (kg) will be recorded for analysis.	Visit 1B (Week 1) and Visit 2B (Week 4): 10 minutes each

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Gastrointestinal Symptoms Questionairre (GSQ)	Participants will be asked to complete an online version of the Gastrointestinal Symptoms Questionnaire (GSQ). The GSQ is a 29-question self-reported gastrointestinal (GI) screening tool broken up into two subcategories for scoring, one for their GI symptoms experienced today and the other for their GI symptoms experienced in the last 4 weeks. There are also two open-ended question at the end of the survey, one describing any other GI symptoms not addressed in the questionnaire and another addressing normal food consumption. The GSQ will be completed online during Visits 1A and 2A.	Completed During Visit 1A and 2A (10 minutes)
Lean Body Mass	Lean body mass (LBM) will be evaluated using air displacement plethysmography using a calibrated BODPOD (COSMED USA Inc., Concord, CA). Participants will be instructed to remove their shoes, socks, jewelry, and all additional clothing other than their base layer. Participants will then be given a swim cap to wear and body composition analysis will be performed per the manufacturer's guidelines.	Visit 1A (Week 1) and Visit 2A (Week 4): 20 minutes each
Body Fat Percentage	Body fat percentage (BF%) will be evaluated using air displacement plethysmography using a calibrated BODPOD (COSMED USA Inc., Concord, CA). Participants will be instructed to remove their shoes, socks, jewelry, and all additional clothing other than their base layer. Participants will then be given a swim cap to wear and body composition analysis will be performed per the manufacturer's guidelines.	Visit 1A (Week 1) and Visit 2A (Week 4): 20 minutes each
Immune Status Questionnaire (ISQ)	Participants will be asked to complete a paper version of the Immune Status Questionnaire (ISQ). The ISQ consists of 7 items rating the respondent's past year's immune status, by inquiring about the incidence of specific immune-related complaints. The ISQ helps to establish participant's perceived immune fitness based on the previous 12 months incidence of disease symptoms. The ISQ utilizes a 0-4 Likert scale to evaluate incidence of these symptoms where a 0 indicates "Never" and a 4 indicates "Always (Almost)." The raw scores are added and converted into a final score where a final score of 0 indicates "very poor perceived immune status," while a final score of 10 indicates "excellent perceived immune status." Final scores less than 6 will be classified as reduced perceived immune function.	Visit 1A (Week 1): 5 minutes
CWI Perceptions Qualitative Assessment	Participants will be asked to complete a qualitative questionnaire to indicate their perceptions of cold water therapy before and after the study. The purpose of this assessment is to see if participants' perceptions changed throughout the study. Further, this questionnaire allows participants to provide any extra qualitative feedback to gain a comprehensive insight on their chronic CWI experience. No scale is used in this survey; however, participants are given the opportunity to report their perceptions of cold immersion using the following choices: increases energy, reduces anxiety, improves sleep, improves mental health, improves physical health, improves immune system, reduces soreness or pain, or other [text response].	Visit 1A (Week 1) and Visit 2A (Week 4): 10 minutes each
Visual Analogue Scale (VAS) of Discomfort	During each session of cold therapy, participants will be assessed on their subjective ratings of discomfort as they acclimate to the cold exposure. During (at 1-minute mark) cold-water immersion, participants will be presented with the Visual Analogue Scale (VAS) of Discomfort, a modified version of a 0-10 item pain scale. This version of the VAS is a subjective measure of discomfort using a 11-point Likert scale ranging from 0 - 10 with 0 indicating "No Discomfort" and 10 indicating "Maximal Discomfort."	Each CWI Intervention Session: 10 seconds

Collaborators and Investigators

• Sponsor: University of Northern Colorado

Study record dates

Study Major Dates

• Study Start (Actual): October 10, 2024
• Primary Completion (Actual): February 1, 2026
• Study Completion (Actual): March 1, 2026

Study Registration Dates

• First Submitted: October 10, 2024
• First Submitted That Met QC Criteria: October 29, 2024
• First Posted (Actual): October 31, 2024

Study Record Updates

• Last Update Posted (Actual): March 10, 2026
• Last Update Submitted That Met QC Criteria: March 7, 2026
• Last Verified: November 1, 2025

More Information

Terms related to this study

• Keywords: Inflammation; Mental Health; Immune Function; Healthy Adults; Gut Health; Cold Water Immersion; Muscular Strength; Cold Tub; Cold Shower
• Additional Relevant MeSH Terms: Pathologic Processes; Pathological Conditions, Signs and Symptoms; Behavior; Personal Satisfaction; Inflammation; Psychological Well-Being; Investigative Techniques; Epidemiologic Research Design; Epidemiologic Methods; Research Design; Methods; Control Groups
• Other Study ID Numbers: 2404058883

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: All study documents will be made available upon reasonable request (Laura.stewart@unco.edu).
• IPD Sharing Time Frame: Oct 1, 2025 - Oct 1, 2028
• IPD Sharing Access Criteria: Individuals will email Laura.stewart@unco.edu with a request for study materials.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No