High-altitude exercise performance and acute mountain sickness unchanged following cold water habituation.
Level 2 - randomized trial
Individual randomized controlled trial
PubMed 42030202 · doi:10.1152/ajpregu.00149.2025
What was done
Participants underwent either repeated cold-water immersion (six 10-minute immersions in 12°C water) or thermoneutral water immersion control before a 29-hour exposure to hypobaric hypoxia (~4,100 m). Investigators evaluated resting and submaximal exercise (50% peak oxygen uptake) physiological responses, two-mile time trial performance, and acute mountain sickness incidence and severity.
What was found
Cold habituation was achieved during immersion, showing an ~20% reduction in peak minute ventilation and ~31% reduction in 10-minute average minute ventilation. Under hypobaric hypoxia at 3 hours, exercise ventilation was higher after cold immersion (+3.8 L/min, 95% CI: 0.8 to 6.7, P = 0.014) without improved oxygen saturation (thermoneutral: 76 ± 4% vs. cold: 76 ± 4%, P > 0.05). Exercise heart rate was elevated across altitude duration (+5 beats/min, 95% CI: 1 to 8, P = 0.030). Two-mile time trial performance and acute mountain sickness symptomology were unchanged.
Why it matters
This study demonstrates that cold-water habituation fails to provide beneficial cross-adaptation to hypobaric hypoxia. It challenges the assumption that cold habituation can prevent acute mountain sickness or enhance physical capacity at high altitude.
Limits
Participant sample size, sex, age, and baseline fitness levels were not reported in the abstract. Exposure was restricted to a 29-hour hypobaric chamber protocol at ~4,100 m, which may not capture longer-term acclimatization dynamics.