Aerobic power and body size affects the exercise-induced stress hormone responses to varying water temperatures.
Level 3 - non-randomized controlled study
Controlled repeated-measures laboratory physiological experiment with unspecified randomization order.
What was done
Eleven active male subjects performed 30 minutes of cycle ergometry at 60% VO2max while immersed to the neck in four different water temperatures: 20°C, 25°C, 30°C, and 35°C. Researchers measured changes in core rectal temperature, plasma cortisol, and urinary excretion of catecholamines (norepinephrine, epinephrine, and dopamine). Multiple regression analyses assessed how anthropometric measures (BMI, body fat) and aerobic fitness (VO2max) influenced these endocrine responses.
What was found
Change in core temperature was significantly associated with water temperature (p < 0.007). Net plasma cortisol increased during exercise in 20°C water and decreased in 30°C and 35°C water (p = 0.011). Catecholamine excretion was generally higher at 20°C and 35°C compared to 25°C and 30°C, with dopamine and norepinephrine significantly higher at 35°C than 25°C (p < 0.05). In multiple regression, cortisol response in 20°C water correlated with VO2max and core temperature change (p < 0.05), while in 35°C water it correlated with BMI and core temperature change (p < 0.05). In 20°C water, body fat was the only consistent partial correlate for norepinephrine and epinephrine excretion.
Why it matters
This study shows that individual aerobic capacity and body composition alter endocrine stress responses when exercising under cold versus warm water immersion.
Limits
The sample size was very small (n = 11) and limited solely to active males. The abstract does not report baseline hormone values, exact effect sizes, or whether the sequence of water temperature exposures was randomized.
Cited by
- contradicts Scientific evidence shows that deliberate cold exposure increases adrenaline and peripheral dopamine while lowering cortisol.