'Cross-adaptation': habituation to short repeated cold-water immersions affects the response to acute hypoxia in humans.
Level 2 - randomized trial
Controlled experimental laboratory trial with a control group (randomization not explicitly stated in abstract)
PubMed 20643773 · doi:10.1113/jphysiol.2010.193458
What was done
Thirty-two male volunteers performed 10-minute bouts of rest and recumbent cycling exercise (100 W) under normoxia and acute hypoxia (FIO2 0.12). Over a subsequent 96-hour period, participants completed six 5-minute immersions in either cold water (12°C, CW group) or thermoneutral water (35°C, TW control group) before repeating the baseline testing protocol. Venous catecholamines (adrenaline, noradrenaline) and heart rate variability (log-transformed high-frequency power, ln HF) were measured immediately following and during the final 5 minutes of each trial bout.
What was found
Compared to their initial hypoxic exposure, the CW group showed increased ln HF power (P < 0.001) and reduced adrenaline (P < 0.001) and noradrenaline (P < 0.001) during the second hypoxic exercise bout. In direct comparison to the TW group during repeat hypoxic exercise, the CW group had lower adrenaline (P = 0.042) and noradrenaline (P = 0.003), though between-group ln HF power did not differ significantly overall. When stratified by baseline sensitivity, ln HF was higher in the hypoxic-sensitive CW subgroup than in any other subgroup. Absolute numerical values for catecholamines and HRV were not reported in the abstract.
Why it matters
This study provides evidence for environmental cross-adaptation in humans, demonstrating that habituation to cold water can cross-tolerance and attenuate sympathetic nervous system reactivity during acute hypoxic stress.
Limits
The study sample was small (n = 32) and restricted exclusively to male volunteers. The abstract does not report baseline numbers, numerical means, or whether participants were randomized. Stress exposures were limited to short, 10-minute acute bouts, leaving the duration of cross-adaptation and functional performance at altitude unmeasured.
Cited by
- context Published scientific literature shows that cold exposure improves resilience to subsequent psychological stressors.