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CompletedNCT06667479Updated Oct 7, 2026

Cold Water Exposure and Immune Function Study

An interventional study of Cold Water Immersion (CWI) - Cold Tub Immersion (CI) and Cold Water Immersion (CWI) - Cold Shower (CS) in Cold Water Immersion, Immune Function and Muscular Strength, sponsored by University of Northern Colorado. Completed at 1 site in United States. Open to participants aged 18 Years to 45 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-10-07.

Sponsored by University of Northern Colorado · Not applicable, Interventional, and Other

Updated Oct 7, 2026Primary outcomes revisedGo to Updates ↓
Phase
Not applicable
Study type
Interventional
Enrollment
37
Allocation
Randomized
Ages
18 Years to 45 Years
Sex
All
01

Study summary

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
02

Conditions studied

  • Cold Water Immersion
  • Immune Function
  • Muscular Strength
  • Mental Health

Keywords

  • Cold Water Immersion
  • Cold Tub
  • Cold Shower
  • Immune Function
  • Mental Health
  • Muscular Strength
  • Healthy Adults
  • Inflammation
  • Gut Health
03

In context

Psychological Well-Being

971 studies on the registry are indexed under Psychological Well-Being; 502 are open to participants now.

This study's enrollment of 37 is below the median of 116 across 830 interventional studies indexed under Psychological Well-Being.

Browse Psychological Well-Being studies →

Lead sponsor

University of Northern Colorado is the lead sponsor of 7 studies on the registry; 1 is open to participants now.

Counted across the registry records on this site, refreshed daily.

04

Who can participate

Ages eligible
18 Years to 45 Years
Sexes eligible
All
Accepts healthy volunteers
Yes

Inclusion criteria

  • Males and Females
  • Aged 18-45

Exclusion criteria

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
05

Study design

Phase
Not applicable
Primary purpose
Other
Allocation
Randomized
Intervention model
Parallel assignment
Masking
None (open label)
Enrollment
37 participants (actual)

Study arms

  • 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)

  • 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)

  • Other
    Control Group (CO)

    Participants will not undergo any cold tub or cold shower intervention.

    Other: Control Group (CO)

Interventions

  • OtherCold 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.

  • OtherCold 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

  • OtherControl 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.

06

What researchers measure

Primary outcomes

  1. 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.

    Time frame: Visit 1A (Week 1) and 2A (Week 4): 10 minutes each

  2. 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.

    Time frame: Visit 1A (Week 1) and Visit 2A (Week 4): 15 minutes for blood draw. The assay itself takes 3 hours.

  3. 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.

    Time frame: Visit 1A (Week 1) and Visit 2A (Week 4): 15 minutes for blood draw. The assay itself takes 3 hours.

Secondary outcomes

  1. 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.

    Time frame: Visit 1A (Week 1) and 2A (Week 4): 10 minutes each

  2. 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.

    Time frame: Visit 1B (Week 1) and Visit 2B (Week 4): 10 minutes each

Other outcomes

  1. 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.

    Time frame: Visit 1A (Week 1) and Visit 2A (Week 4): 20 minutes each

  2. 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.

    Time frame: Visit 1A (Week 1) and Visit 2A (Week 4): 20 minutes each

  3. 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.

    Time frame: Visit 1A (Week 1): 5 minutes

  4. 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 \[text response\].

    Time frame: Visit 1A (Week 1) and Visit 2A (Week 4): 10 minutes each

  5. 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.

    Time frame: Completed During Visit 1A and 2A (10 minutes)

  6. 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."

    Time frame: Each CWI Intervention Session: 10 seconds

07

Study locations

1 site
  • University of Northern Colorado - Gunter Hall
    Greeley, Colorado 80631, United States
08

References and documents

Individual participant data

Plan to share: Yes — All study documents will be made available upon reasonable request (Laura.stewart@unco.edu).

No publications or documents are linked to this record.

09

Updates

1 registry update since Sep 25, 2026
Also revised
primary outcomes
Show all 1 update
  1. Oct 7, 2026
    Primary outcomes Revised (1 change)
    + 1 other change: secondary outcomes

From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗

10

Registry details

Key details

Study ID
NCT06667479
Lead sponsor
University of Northern Colorado
Responsible party
Laura Stewart (Professor, University of Northern Colorado) — Principal investigator
First posted
Oct 31, 2024
Start date
Oct 10, 2024
Primary completion
Feb 1, 2026
Completion
Mar 1, 2026
Last update
Oct 7, 2026

Oversight

Data monitoring committee
No
FDA-regulated drug
No
FDA-regulated device
No
View the source record on ClinicalTrials.gov ↗

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