Use of Self-Induced Hypnosis to Modify Thermal Balance during Cold Water Immersion

This study was designed to evaluate the efficacy of self-induced post-hypnotic suggestion to improve physical and thermogenic responses to two cycles of alternating rest and exercise during head-out immersion in 25 C water. Twelve U.S. Navy divers volunteered to participate in two immersions conducted at the same time of day but spaced one week apart. The first immersion (control) was conducted prior to hypnotic training sessions on mental imagery and post- hypnotic suggestion techniques. There were no differences in rates of heat production, heat loss or net thermal balance between control and hypnotic conditions for the grouped values. Hypnotic susceptibility, evaluated prior to the immersions, was not significantly correlated with the change in thermal balance or rectal temperature measurements evaluated between control and hypnotic immersions. Although the rating of perceived exertion during both exercise phases were similar for both immersions, subjects' perceived thermal sensation was reduced during the second rest phase of the hypnotic immersions when compared with the control immersion. Although the majority of subjects did not exhibit a hypnotic-induced alteration in thermoregulatory responses during immersion, 3 individuals seemed to respond to hypnosis, but in a manner that accentuated heat loss. These results suggest that the post-hypnotic training techniques employed in the present study did not enhance performance in divers during immersion in 25 C. (SDW)