Residual effects of short-term whole-body cold-water immersion on the cytokine profile, white blood cell count, and blood markers of stress.
Level 4 - case-series / case-control
Uncontrolled before-and-after laboratory experimental study
PubMed 33910456 · doi:10.1080/02656736.2021.1915504
What was done
Healthy, non-acclimated young adult men (aged 20–30 years) underwent short-term whole-body cold-water immersion (14 °C for 10 minutes). Researchers measured physiological stress indicators (heart rate, shivering, hyperventilation, metabolic heat), stress hormones (epinephrine, norepinephrine, cortisol), leukocyte subsets (neutrophils, lymphocytes), proinflammatory cytokines (TNF-α, IL-1β, IL-6), and symptoms of the common cold over a 48-hour post-immersion period.
What was found
The abstract reports directional outcomes without numerical data, effect sizes, or p-values. Immersion induced acute physiological stress (hyperventilation, shivering, metabolic heat production, increased heart rate) and marked release of epinephrine, norepinephrine, and cortisol. After immersion, TNF-α production decreased, IL-6 concentration showed a delayed response, and IL-1β levels remained unchanged across 48 hours. Leukocyte profiling showed a delayed increase in neutrophil percentage and a decrease in lymphocyte percentage. No participants developed symptoms of the common cold within the 48-hour follow-up.
Why it matters
It characterizes the acute endocrine and immune response to cold stress, suggesting brief cold-water immersion alters stress markers and specific cytokines without immediately triggering common cold symptoms.
Limits
The abstract does not disclose the sample size, numerical values, variability, or statistical significance levels. There was no control or sham-immersion comparison group. The study was restricted exclusively to non-acclimated young men (20–30 years old), limiting generalizability to women, older adults, or cold-adapted individuals. The 48-hour follow-up is too brief to evaluate longer-term immune adaptation or delayed infections.