The effects of an application of suncream on selected physiological variables during exercise in the heat

Background. The purpose of this study was to investigate the effects of an application of suncream on mean skin temperature (MST), rectal temperature (Tre), oxygen consumption and heart rate during exercise in the heat. Methods. Twenty-two male subjects underwent two steady state exercise tests (55% of maximum oxygen consumption, mean work rate 153 watts) for 40 minut es (following a 5 minute warm-up), under two treatment conditions at the sa me ambient temperature (32 degrees C, 54% relative humidity). One treatment involved wearing an application of suncream (SC) while the other treatment did not (NSC). Suncream was applied in the amount of 30 ml/m(2) of body su rface area. Results. Results of this study indicated that an application of suncream si gnificantly reduced MST, on average. 31 degrees C, during exercise in the h eat (p=0.03). However, further statistical analysis revealed that this was a function of a significant interaction effect (p=0.001) (main effect is su nscreen; interaction effect sunscreen plus temperature). MST was lower for the SC condition versus NSC over all time measurements. Results also showed a significant difference in the mean core to skin temperature gradient (p= 0.001), with a greater gradient existing in the SC condition. There did not appear to be any effect of suncream on ventilation, rectal temperature, ox ygen consumption, lactate levels, sweat loss, percent plasma volume change, rating of perceived exertion, or respiratory exchange ratio. Interestingly , although not statistically significant (p=0.18), rectal temperature remai ned lower, on average 0.1 degrees C, under the SC condition for every measu rement throughout the exercise session. Conclusions. In conclusion, results of this preliminary study suggest that an application of suncream does not impair heat dissipation as indicated by a decreased MST and increased core to skin thermal gradient.