THE EFFECTS OF WARMING BY ACTIVE AND PASSIVE MEANS ON THE SUBSEQUENT RESPONSES TO COLD-WATER IMMERSION

Two experiments were undertaken to investigate the effects of warming the body upon the responses during a subsequent cold water immersion ( CWI). In both experiments the subjects, wearing swimming costumes, und ertook two 45-min CWIs in water at 15-degrees-C. In experiment 1, 12 s ubjects exercised on a cycle ergometer until their rectal temperatures (T(re)) rose by an average of 0.73-degrees-C. They were then immediat ely immersed in the cold water. Before their other CWI they rested sea ted on a cycle ergometer (control condition). In experiment 2, 16 diff erent subjects were immersed in a hot bath (40-degrees-C) until their T(re) rose by an average of 0.9-degrees-C; they were then immediately immersed in the cold water. Before their other CWI they were immersed in thermoneutral water (35-degrees-C; control condition). Heart rate i n both experiments and respiratory frequency in experiment 1 were sign ificantly (P < 0.05) higher during the first 30 s of CWI following act ive warming. In experiment 1, the rate of fall of T(re) during the fin al 15 min of CWI was significantly (P < 0.01) faster when CWI followed active warming (2.46-degrees-C . h-1) compared with the control condi tion (1.68-degrees-C . h-1). However, this rate was observed when abso lute T(re) was still above that seen in the control CWIs. It is possib le, therefore, that if longer CWIs had been undertaken, the two temper ature curves may have converged and thereafter fallen at similar rates ; this was the case with the aural temperature (T(au)) seen in experim ent 1 and the T(au) and T(re) in experiment 2. It is concluded that pr e-warming is neither beneficial nor detrimental to survival prospects during a subsequent CWI.