Effects of Ice-Pack Application on Hand Skin Temperature and Subjective Thermal Sensation and Comfort in Healthy Young Men: A Randomized, Parallel-Group Controlled Trial
Phase: NA
Conditions: Cold Exposure, Body Temperature Regulation, Thermal Comfort Perception
Sponsor: Poznan University of Physical Education

Study Protocol: Hand Ice‑Pack Cryotherapy vs Thermoneutral Water 
Pack in Healthy Volunteers 
Version 1.0 — 2025-10-03 
Version 1.0 — 2025-10-03 
 
1. Administrative Information 
1.1 Short title 
Hand Ice‑Pack vs Thermoneutral Pack RCT 
 
1.2 Trial registration 
Not prospectively registered (laboratory, minimal‑risk, non‑therapeutic investigation). 
 
1.3 Protocol version and date 
Version 1.0; 2025-10-03. 
 
1.4 Roles and responsibilities 
Sponsor/Institution: Poznań University of Physical Education (Department of Physical Therapy 
and Sports Recovery). 
Scientific lead: [Paweł Korman], PhD. Data management/statistics: [Ewa Śliwicka], MSc. Thermal 
imaging lead: [Manuel Sillero-Quintana ], MSc. 
Corresponding author: [Paweł Korman], [pkorman@awf.poznan.pl]. 
 
2. Background and Rationale 
Local cryotherapy with ice packs is widely used to alleviate pain and modulate cutaneous 
temperature and sensation. However, the short‑term time‑course of rewarming and 
contemporaneous changes in subjective thermal perception and somatosensory thresholds are not 
fully characterised in controlled, randomized settings. This study compares a 15‑minute hand 
ice‑pack application with a thermoneutral water‑pack control, using infrared thermography (IRT) 
and a resistance thermometer (RT) alongside validated subjective scales and quantitative sensory 
testing (QST). 
 

3. Objectives 
Primary objective: 
• To compare the effect of ice‑pack vs thermoneutral pack on dorsal hand skin temperature (Tsk) 
during early rewarming after a 15‑minute application. 
 
Secondary objectives: 
• To compare immediate post‑cooling changes in mechanical detection threshold (MDT) and 
vibration detection threshold (VDT). 
• To compare trajectories and peaks of subjective thermal sensation (TSS), thermal comfort (CS), 
and pain (VAS) during cooling and immediately post‑cooling. 
• To characterise agreement and systematic offset between ROI‑averaged IRT and single‑site RT 
across matched time points. 
 
4. Trial Design 
Randomized, parallel‑group, two‑arm laboratory experiment with a 1:1 allocation ratio (ice vs 
thermoneutral water). Single‑centre. No blinding of participants; thermal image analysis performed 
offline by a rater not involved in data collection. 
 
5. Study Setting 
Single air‑conditioned laboratory (Department of Physical Therapy and Sports Recovery, Poznań 
University of Physical Education). Ambient conditions monitored throughout (target ~22.5 ± 1.0 
°C, 55 ± 7% RH). 
 
6. Participants 
6.1 Eligibility criteria 
Inclusion: healthy males, university students, good general health, no history of 
neck/upper‑quadrant pain. 
Exclusion: diabetes; thyroid or other endocrine disorders; significant spinal pain; generalised 
neurological/rheumatological disorders; regular analgesic or psychotropic medication use. 
 
6.2 Recruitment 
Oral announcements among university student population. 

 
6.3 Informed consent 
Written informed consent obtained prior to any procedures. 
 
7. Interventions 
7.1 Cooling intervention (experimental) 
Commercial plastic ice bag (Ø 22.86 cm; capacity ~946 ml). Filled with 400 g of pre‑portioned 
cylindrical ice cubes (20 g each). Applied to the dorsal hand, ~1 cm proximal to the wrist joint line, 
covering fingers. Duration: 15 minutes. 
 
7.2 Thermoneutral control 
Same bag, filled with water at thermoneutral temperature (equal to current limb temperature ± 0.5 
°C), mass‑matched to 400 g. Same placement and duration. 
 
7.3 Concomitant care 
Participants refrained from topical agents on hands 24 h prior; abstained from smoking, alcohol, 
coffee, intense exercise on test day. Hands washed/degreased ≥ 1 h before data collection. 
 
8. Outcomes and Endpoints 
8.1 Primary endpoint 
• Minimum dorsal hand Tsk during the 30‑minute rewarming window (IV–X) measured by IRT 
(ROI mean); between‑group difference (ice vs control). 
 
8.2 Key secondary endpoints 
• Dorsal hand Tsk at matched time points (I, IV–X) by IRT and RT; between‑group differences and 
IRT–RT offsets. 
• MDT change (post‑cooling minus baseline; IV–I). 
• VDT change (IV–I). 
• Subjective scales: TSS (−4 very cold … +4 very hot), CS (1 comfortable … 5 extremely 
uncomfortable), VAS pain (0–100 mm). Outcomes include peak during cooling (II/III) and 
immediate post‑cooling (IV). 

 
8.3 Safety/harms 
Monitoring for intolerance to cold (excess pain, numbness), skin irritation, or adverse events (e.g., 
frostbite risk). None anticipated under protocol; record and report any events. 
 
9. Time Schedule of Enrolment, Interventions, and Assessments 
Acclimatisation: 15 minutes (supine, hand supported on insulating mat). 
Measurements at the following time points: 
I – end of acclimatisation (baseline) 
II – 7th minute of cooling 
III – 15th minute of cooling 
IV – immediately after removing the pack 
V – 5th minute of rewarming 
VI – 10th minute of rewarming 
VII – 15th minute of rewarming 
VIII – 20th minute of rewarming 
IX – 25th minute of rewarming 
X – 30th minute of rewarming 
 
Schedule (✔ = administered): 
• IRT (ROI mean Tsk): I, IV–X (eight images total) 
• RT (single‑site Tsk): continuous at 1‑min; aligned to I–X for analysis 
• TSS, CS, VAS: I, II, III, IV 
• QST (MDT, VDT): I and IV 
 
10. Data Collection Methods 
10.1 Infrared thermography (IRT) 

FLIR SC640 (NETD < 30 mK, 640×480, ±2% accuracy). Perpendicular camera mounting at ~90 
cm. Emissivity set to 0.98; ambient control per guidance. ROI template on dorsal hand up to the 
wrist line. Software: Thermacam Researcher Pro 2.10. Images analysed offline by trained rater; 
10% re‑analysed for intra‑rater consistency. 
 
10.2 Resistance thermometer (RT) 
Contact sensor (~15 mm²) affixed between 3rd–4th metacarpals, mid‑distance between wrist and 
MCP joints, secured with medical tape. 1‑min sampling from acclimatisation start to end of 
rewarming. Two‑point check vs reference thermometer before each session. 
 
10.3 Quantitative sensory testing (QST) 
MDT: Semmes–Weinstein monofilaments (1.65–6.65; 0.008–300 g), vertical application until 
bending, ~1 s contact; up‑down method, threshold from central tendency. 
VDT: Rydel–Seiffer tuning fork (64 Hz; 0–8/8 scale), three trials over a bony landmark; mean of 
three readings. 
 
10.4 Subjective scales 
TSS (−4…+4; anchors from very cold to very hot), CS (1…5; comfortable to extremely 
uncomfortable), VAS pain (0–100 mm; no pain to worst pain imaginable). Scripted instructions by 
the same assessor. 
 
11. Sample Size 
An a priori power analysis (G*Power 3.1.9.7) for a two-tailed independent-samples t-test (α = 0.05, 
power = 0.80, anticipated effect size d = 0.80) indicated a required sample of 26 participants per 
group (total n = 52). In practice, 39 participants were enrolled and randomised (experimental n = 
20; control n = 19). Of 40 individuals assessed, one was excluded at screening for a health 
condition. No participants discontinued the intervention or were lost to follow-up. With the 
achieved sample size, post-hoc power to detect d = 0.80 was approximately 0.68; accordingly, 
findings are interpreted as exploratory/hypothesis-generating. 
12. Randomization and Allocation 
12.1 Sequence generation 

A simple 1:1 computer-generated randomization sequence (no blocking or stratification; 
superiority framework) was prepared by Paweł Korman to map numeric study IDs to groups (ice 
pack vs thermoneutral control). Korman had no access to personal identifiers. 
12.2 Allocation concealment and implementation 
At registration, participants received numeric study IDs (ID001–ID039) assigned by Piotr 
Szałański. The identity–ID linkage was held by the registrar. Group assignments were concealed 
until completion of baseline assessments and were disclosed immediately before the intervention. 
No sequentially numbered opaque sealed envelopes or centralized web-based randomization 
system were used. 
12.3. Blinding 
Participants and interventionists were not blinded. Thermal image analysis was performed offline 
by an assessor not involved in data collection. Raw-data preprocessing/curation (Manuel Sillero-
Quintana) and statistical analyses (Ewa Śliwicka) were conducted by team members who did not 
take part in the experimental procedures and were blinded to group allocation. 
13. Statistical Analysis Plan (SAP) 
• 
Descriptives: values as mean ± SD; Table 1 additionally reports min–max where shown. 
• 
Normality: Shapiro–Wilk test. 
• 
Between-group comparisons at prespecified time points: Student’s t test (normal) or 
Mann–Whitney U test (non-normal). 
• 
Within-group pre–post comparisons: paired Student’s t test (normal) or Wilcoxon signed-
rank test (non-normal). 
• 
Repeated measures: two-way repeated-measures ANOVA for Tsk (group × stage; and IRT 
vs RT within groups), with Bonferroni-adjusted post hoc tests. Effect size: partial η² for RM-
ANOVA. 
• 
Significance: α = 0.05; tests two-sided. 
• 
Analysis set / missing data: all randomised participants analysed; no imputation (no losses). 
 
14. Data Management and Sharing 
De-identified individual participant data (IPD) and the de-identified summary datasets underlying 
all tables and figures are openly available in Zenodo (DOI: 10.5281/zenodo.17255092) under a CC 
BY 4.0 license, with no access restrictions or data-use agreement required. The Zenodo record also 
includes Supplementary File S1 (exact questionnaire wording/anchors) and the full Research 
Protocol and prespecified Statistical Analysis Plan. De-identified IPD comprise participant-level 
values for prespecified outcomes and baseline characteristics; direct identifiers, dates, free-text 
fields, and rare categories were removed or aggregated to minimise re-identification risk. The 
dataset will be preserved for at least 5 years; enquiries may be directed to the corresponding author. 
15. Ethics 

Approved by the Bioethics Committee of the Poznań University of Medical Sciences (Resolution 
No. 360/11). Conducted in accordance with the Declaration of Helsinki. Minimal risk expected. 
 
16. Monitoring and Harms 
Adverse events (e.g., excessive pain, skin irritation) monitored throughout; any event recorded with 
timing, severity, relatedness, and action taken. No interim analyses; trial duration per session ~60–
75 minutes. 
 
17. Amendments and Deviations 
Any protocol deviations or amendments will be documented with rationale, date, and potential 
impact on outcomes; none planned at this stage. 
 
18. Dissemination 
Results to be submitted to a peer‑reviewed journal and presented at scientific meetings. Participants 
can request a lay summary.