Original articles   

The Journal of Sports Medicine and Physical Fitness 2000 March;40(1):35-40

Copyright © 2002 EDIZIONI MINERVA MEDICA

lingua: Inglese

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

Connolly D. A. J., Wilcox A. R.

From the Human Performance Laboratory Program in Physical Education University of Vermont, Burlington, USA * Department of Exercise and Sport Science Oregon State University, Corvallis, USA

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 min­utes (fol­low­ing a 5 min­ute ­warm-up), ­under two treat­ment con­di­tions at the ­same ambi­ent tem­per­a­ture (32°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/m2 of ­body sur­face ­area.
Results. Results of ­this ­study indi­cat­ed ­that an appli­ca­tion of sun­cream sig­nif­i­cant­ly ­reduced MST, on aver­age. 31°C, dur­ing exer­cise in the ­heat (p=0.03). However, fur­ther sta­tis­ti­cal anal­y­sis ­revealed ­that ­this was a func­tion of a sig­nif­i­cant inter­ac­tion ­effect (p=0.001) (main ­effect is sun­screen; 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, oxy­gen 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 ­remained low­er, on aver­age 0.1°C, ­under the SC con­di­tion for eve­ry meas­ure­ment 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.