THERMOREGULATION IN SURFERS AND NON-SURFERS IMMERSED IN COLD WATER

  • 1 January 1978
    • journal article
    • research article
    • Vol. 5  (4) , 377-390
Abstract
During immersion to the neck in 19 .+-. 0.6.degree. C water, surfers maintained higher toe temperatures than nonsurfers. The Lewis hunting response was seen only in the surfers toes. The shivering response of the surfers occurred later and was less intense. Threefold increases in metabolic heat production (140 kcal/m2-h) above rest level were found in both groups. Rectal temperature changes were similar in both groups, with a mean decline of 1.2.degree. C over the 1 h exposure period. Individual changes in rectal temperature were negatively correlated to percent of body fat. An initial hyperventilation upon immersion was followed 1st by a decline and then by a rise to 3 times that of rest. A transient rise in heart rate (35 beats/min) occurred in the initial stage of immersion in both groups and subsequently fell to basal levels, rising slightly thereafter. Sinus arrhythmias were observed during the 1st few min of immersion. In nonsurfers, plasma cortisol approximated the decrease anticipated because of the circadian cycle but was elevated in the surfers. Plasma volume decreased 12.2% (surfers) and 17.6% (nonsurfers). Diuresis was observed in both groups. It was 3.2 and 5.0 ml/min for surfers and nonsurfers, respectively.