Key result
Unilateral 5°C forearm immersion drives a ~50% greater perfusion drop versus the non-immersed limb.
Why the study?
The study was conducted to quantify bilateral cutaneous microvascular responses to unilateral forearm cold-water immersion and describe concurrent autonomic cardiac responses.
Does unilateral 5 °C forearm cold-water immersion alter bilateral microvascular perfusion and autonomic cardiac responses in healthy adults?
RCT (n=30)
Open-label
Randomized allocation sequence assigning participants to either right- or left-forearm immersion
No
Does unilateral 5 °C forearm cold-water immersion alter bilateral microvascular perfusion and autonomic cardiac responses in healthy adults?
Mean Difference: 50 (95% CI 48.7–51.2)
Absolute Event Rate: 60.2% vs 10.3%
p-value: p=<0.001
Unilateral cold-water immersion induces strong local vasoconstriction with minor contralateral changes and concurrent systemic autonomic activation.
Local vasoconstriction predominates with unilateral cold exposure in healthy adults; leaves open translation to clinical populations or therapeutic contexts.
OBJECTIVES: To quantify bilateral cutaneous microvascular responses to unilateral forearm cold-water immersion (CWI) and describe concurrent autonomic cardiac responses. METHODS: Thirty healthy adults completed a within-subject bilateral experiment with randomized unilateral 5 °C forearm immersion. Bilateral fingertip perfusion was recorded by laser Doppler flowmetry (LDF), and heart rate variability was recorded continuously. primary endpoint was the within-participant ipsilateral-contralateral difference in relative perfusion decrease from baseline to nadir during cold exposure. Secondary endpoints were LDF kinetic and recovery outcomes, and heart rate (HR) and heart rate variability (HRV) outcomes were treated as secondary autonomic outcomes. HRV-contralateral perfusion associations were exploratory. RESULTS: Resting perfusion was similar between limbs (mean difference, -0.07 perfusion units; 95% CI, -0.22 to 0.08; p = 0.370). For the primary endpoint, the immersed limb showed a greater relative perfusion decrease than the contralateral limb (60.2 ± 2.8% vs. 10.3 ± 1.2%; mean difference, 50.0% points; 95% CI, 48.7 to 51.2; dz = 15.28; adjusted p < 0.001). Secondary LDF endpoints showed earlier vasoconstriction, delayed post-removal peak perfusion, higher peak perfusion, and longer recovery in the immersed limb. Heart rate increased by 9.21 bpm, whereas RMSSD and SDNN decreased by 9.28 and 7.44 ms, respectively (all adjusted p < 0.001). Exploratory HRV-contralateral perfusion correlations were not significant. CONCLUSIONS: Unilateral 5 °C forearm immersion elicited a dominant local vasoconstrictive-hyperemic response, smaller contralateral changes, and concurrent autonomic cardiac activation.
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Hagner–Derengowska et al. (2026) conducted an RCT in Healthy adults (n=30). Unilateral forearm cold-water immersion vs. Non-immersed contralateral limb was evaluated on Within-participant ipsilateral-contralateral difference in relative perfusion decrease from baseline to nadir during cold exposure (MD 50.0, 95% CI 48.7 to 51.2, p=<0.001). Unilateral 5 °C forearm cold-water immersion elicited a 50.0 percentage point greater relative perfusion decrease in the immersed limb compared to the non-immersed contralateral limb.
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