The Effects of Cold Adaptation on Skin Blood Flow, Hand Function, and Comfort in Healthy Adults

The Effects of Cold Habituation on Peripheral Blood Flow, Hand Function, and Thermal Comfort

In cold weather environments, blood flow to the extremities is significantly reduced, which severely impairs hand function and induces thermal discomfort. Prolonged or repeated cold exposure elicits an adaptive habituation response that is characterized by blunted skin vasoconstriction and thus may be an effective strategy to improve peripheral perfusion, reduce thermal discomfort, and maintain hand function during cold weather military operations. Since mission conditions often involve low ambient temperatures, countermeasures that reduce cold-induced decrements in hand function and thermal comfort are important to enhance Warfighter readiness in cold weather battlefield environments. The goals of this study are to 1) evaluate the effectiveness of cold habituation in improving skin blood flow, hand function, and thermal comfort during cold exposure and 2) identify the mechanisms that contribute to improvements in skin blood flow following habituation.

Study Overview

• Status: Completed
• Conditions: Cold Exposure
• Intervention / Treatment: Other: Repeated cold exposure

Detailed Description

Participants (n=15, 18-39 yrs) will complete a preliminary cold air exposure (baseline testing) followed by 8 days of repeated cold air exposures with minimal clothing. The cold exposures will be 2 hours in duration and will be conducted in 8°C (46°F) conditions. Before and after the repeated cold exposures, participants will undergo hand function tests, assessments of thermal comfort, and skin blood flow testing.

• Study Type: Interventional
• Enrollment (Actual): 16
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Massachusetts
    • Natick, Massachusetts, United States, 01760
      • U.S. Army Research Institute of Environmental Medicine

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 39 years (Adult)
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Male or female, age 18-39
• In good health as determined by OMSO (Office of Medical Support and Oversight)
• Willing to refrain from exercise and caffeinated or alcoholic beverages for 12 hours before each testing session
• Willing to refrain from smoking or tobacco use 8 hours before each testing session

Exclusion Criteria:

• History of cold injuries of any severity (e.g., frostbite, trench foot, chilblains).
• Raynaud's syndrome.
• Cold-induced asthma/bronchospasm
• Previous hand/finger injuries that impair dexterity and hand function.
• Metal hardware (plates/screws) in the forearms and hands.
• Current use of medications or dietary supplements that could alter cardiovascular, thermoregulatory, or vascular control (e.g., anti-hypertensives, statins).
• Known allergies to medical adhesives.
• Heart, lung, kidney, muscle, or nerve disorder(s)
• A planned MRI during the study or within 2 days after completing a cold test.
• Women who are pregnant, planning to become pregnant, or breastfeeding.
• Not willing to have small areas of skin on the body shaved (if deemed necessary for attachment of study instrumentation)

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Cold habituation; 8-day cold habituation	Other: Repeated cold exposure; 8 consecutive days of exposure to 8°C air for 120 minutes each day

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Skin blood flow	Skin blood flow will be measured using non-invasive laser-Doppler flowmetry probes before and during cold exposure. Output (red blood cell flux) will be divided by mean arterial blood pressure to give an index of cutaneous vascular conductance [CVC, flux/mmHg].	8 days
Skin temperature	Skin temperatures [in °C] at up to 10 sites on the body will be measured using skin thermistors before and during cold exposure. Hand and foot skin temperatures will also be measured with a thermography imaging camera.	8 days
Manual dexterity - Pegboard	Pegboard scores will be obtained before and during cold exposure. Scores are the number of pegs placed into the boards.	3 days
Manual dexterity - Minnesota Rate of Manipulation	Minnesota Rate of Manipulation dexterity scores will be obtained before and during cold exposure. Scores are the time [in seconds] required to move small blocks various distances.	3 days
Hand and finger strength	Pinch and hand strength [in kg] will be measured using a pinch meter and grip strength device (dynamometer). Participants will complete three pinch strength tests and one grip strength test before and during cold exposure.	3 days
Cold perception	Ratings of thermal comfort, thermal sensation, and pain perception [in arbitrary units] will be assessed using visual analogue scales before and during cold exposure.	5 days

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Metabolic heat production	Oxygen consumption and carbon dioxide production [ml/kg/min] will be measured using computerized indirect calorimetry before and during cold exposure. Oxygen consumption and carbon dioxide production will be combined to report metabolic heat production in Watts per meter squared.	5 days
Body core temperature	Body core temperature [in °C] will be measured using a telemetry pill self-inserted as a suppository during cold exposure.	5 days
Blood pressure	Brachial artery blood pressure [in mmHg] will be measured using an automated blood pressure cuff before and during cold exposure.	12 days
Plasma norepinephrine	Circulating concentrations of norepinephrine [in pg/ml] will be assessed in blood collected via venipuncture before and after cold exposure.	3 days
Heart rate	Heart rate [in beats per min] will be measured using an automated cuff before and during cold exposure.	12 days

Collaborators and Investigators

• Sponsor: United States Army Research Institute of Environmental Medicine
• Investigators: Principal Investigator: Billie K Alba, Ph.D., United States Army Research Institute of Environmental Medicine

Study record dates

Study Major Dates

• Study Start (Actual): August 1, 2022
• Primary Completion (Actual): September 13, 2024
• Study Completion (Actual): September 13, 2024

Study Registration Dates

• First Submitted: July 6, 2022
• First Submitted That Met QC Criteria: July 14, 2022
• First Posted (Actual): July 19, 2022

Study Record Updates

• Last Update Posted (Actual): December 26, 2025
• Last Update Submitted That Met QC Criteria: December 18, 2025
• Last Verified: December 1, 2025

More Information

Terms related to this study

• Other Study ID Numbers: 21-04H; MO210025 (Other Grant/Funding Number: USAMRDC Military Operational Medicine Research Program)

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