The effect of wave motion on dry suit insulation and the responses to cold water immersion

Methods: Six subjects who were each wearing a dry immersion suit system were immersed for 1 h in 16 degrees C water in a number of different wave conditions, ranging from still water to 70 cm in height. Physiological and physical parameters were measured in order to calculate the total thermal resistance of the suit system and its components. Results: None of the physiological parameters were affected significantly by the wave conditions, except for skin heat flux, which increased with wave height from 72.0 +/- 1.9 W . m(-2), at 0 cm of height, to 85.5 +/- 2.9 W. m(-2) at 70 cm of height. Wave heights up to 70 cm decreased the insulation (including boundary layer) of the dry suit system by 14%, and the only component of the suit affected by the wave motion was the insulation of the water boundary layer, which decreased by 75%. The body sites that were most affected by wave motion were the head and the trurk, with an average 45% decrement in suit system thermal resistance at those sites at wave heights of 0 to 70 cm. No significant effect was observed at sites on the distal limbs. Conclusion: To simulate open ocean conditions in the laboratory, the standards must take the reduction of suit insulation into account.