Repeated cold showers as a method of habituating humans to the initial responses to cold water immersion

The hypothesis that the initial responses to cold water immersion could be attenuated by repeated cold showers was tested. Eighteen (13 men, 5 women) non-habituated subjects undertook two 3-min head-out seated immersions into stirred water at 10°C wearing swim wear. The immersions were separated by 4 days during which time they took six cold showers. The subjects were randomly split into three groups with different showering regimes: 3 min at 10°C on the back (10B); 3 min at 15°C on the back (15B); and 30 s at 10°C on the back followed by 30 s on the front (10BF). Over the first 30 s of immersion respiratory frequency ( f _R) was reduced by 21% in groups 10B and 10BF from 54 (14) to 44 (16) breaths.min⁻¹ ( P <0.05), and 33 (8) to 26 (10) breaths.min⁻¹ ( P <0.05) respectively, following repeated showers. Group 15B showed no change in f _R. The tachycardia induced on immersion in water at 10°C was not reduced by repeated showers except in group 15B during the last 150 s [from 119 (23) to 105 (25) beats.min⁻¹, P <0.05]. Repeated showering in water at 10°C reduced the respiratory drive (as measured by f _R) during head-out immersion in water at the same temperature. No such habituation was observed with repeated showers in warmer water (15°C). It is concluded that when the body surface area cooled is the same, the rate of change of skin temperature is an important factor in determining the degree of habituation produced.