The acute thermophysiological effects of sunscreen application to males exercising in hot-dry and hot-humid climates

Abstract

Purpose. The purpose of this study was to investigate the acute thermophysiological responses of college males as they exercised with sunscreen applied to their exposed body surface in hot-dry and hot-humid climates. Procedure. Sixteen college males volunteered for this study and were considered to be average in fitness level and in percent of body fat. This was determined with a branching protocol on the cycle ergometer and hydrostatic weighing, respectively. The subjects then performed four exercise bouts on a cycle ergometer in an environmental chamber kept at a constant 35(DEGREES)C ambient air temperature. The work bouts were conducted one week apart, and the experimental conditions were varied each week by changing the humidity level from low (25 - 35%) to high (65 - 75%) and by either applying or not applying sunscreen. During each experimental session, core temperature (TR), mean skin temperature (TSK), oxygen uptake (VO2) and weight loss (WTLS) were measured for each subject. Each session included 39 minutes of exercise, and all parameters except WTLS and VO2 were recorded at three-minute intervals. A repeated measures three factor factorial design was used to analyze the data. The experimental responses of TR and TSK for five randomly selected subjects were compared to the simulated responses as predicted by the Stolwijk Model. Linear regression was used to analyze this data. Results. The following conclusions were made with respect to the data collected and analyzed for this study: (1) The use of sunscreen as a sun blocking agent during exercise in hot-dry and hot-humid climates increases mean skin temperature. (2) The level of humidity does not appear to alter the effects of sunscreen application during exercise. (3) Application of sunscreen does not adversely affect the predictive accuracy of the Stolwijk Model.