Key result
Prolonged extreme cold water diving for 9 hours decreased core and skin temperatures and increased salivary alpha-amylase by 200-225%.
Why the study?
Prolonged cold water exposure may shift sympathovagal balance toward sympathetic activation, potentially negating the dive reflex and impacting thermoregulation.
Does prolonged extreme cold water diving induce an acute stress response and affect thermoregulation in military divers?
Observational (n=21)
No
Does prolonged extreme cold water diving induce an acute stress response and affect thermoregulation in military divers?
Prolonged extreme cold water diving initiates a measurable acute stress response and decreases peripheral skin temperature, suggesting a relationship between stress and peripheral thermoregulation.
Answers are grounded in this paper and cite their sources.
Associated with acute stress and thermoregulatory shifts in divers; hypothesis-generating and requires prospective validation before clinical adoption.
Introduction: Cold water exposure poses a unique physiological challenge to the human body. Normally, water submersion increases activation of parasympathetic tone to induce bradycardia in order to compensate for hemodynamic shifts and reduce oxygen consumption by peripheral tissues. However, elevated stress, such as that which may occur due to prolonged cold exposure, may shift the sympatho-vagal balance towards sympathetic activation which may potentially negate the dive reflex and impact thermoregulation. Objective: To quantify the acute stress response during prolonged extreme cold water diving and to determine the influence of acute stress on thermoregulation. Materials and Methods: Twenty-one ( n = 21) subjects tasked with cold water dive training participated. Divers donned standard diving equipment and fully submerged to a depth of ≈20 feet, in a pool chilled to 4°C, for a 9-h training exercise. Pre- and post-training measures included: core and skin temperature; salivary alpha amylase (AA), cortisol (CORT), osteocalcin (OCN), testosterone (TEST) and dehydroepiandosterone (DHEA); body weight; blood glucose, lactate, and ketones. Results: Core, skin, and extremity temperature decreased ( p < 0.001) over the 9-h dive; however, core temperature was maintained above the clinical threshold for hypothermia and was not correlated to body size ( p = 0.595). There was a significant increase in AA ( p < 0.001) and OCN ( p = 0.021) and a significant decrease in TEST ( p = 0.003) over the duration of the dive. An indirect correlation between changes in cortisol concentrations and changes in foot temperature ( ρ = -0.5, p = 0.042) were observed. There was a significant positive correlation between baseline OCN and change in hand temperature ( ρ = 0.66, p = 0.044) and significant indirect correlation between changes in OCN concentrations and changes in hand temperature ( ρ = -0.59, p = 0.043). Conclusion: These data suggest that long-duration, cold water diving initiates a stress response—as measurable by salivary stress biomarkers—and that peripheral skin temperature decreases over the course of these dives. Cumulatively, these data suggest that there is a relationship between the acute stress response and peripheral thermoregulation.
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Kelly et al. (2022) conducted an observational in Cold water exposure during military dive training (n=21). Prolonged extreme cold water diving (4°C) vs. Pre-dive baseline was evaluated on Change in core/skin temperature and salivary stress biomarkers (alpha-amylase, osteocalcin, testosterone) (p=<0.001). Prolonged extreme cold water diving for 9 hours decreased core and skin temperatures and increased salivary alpha-amylase by 200-225%.
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