A synthetic undergarment increases physiological strain

Matthew C. Dorton, Brent C. Ruby, Charles L. Dumke

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


Our aim was to examine the effect of a synthetic material undergarment on heat stress during exercise in a hot environment. Ten active males completed two trials of intermittent (50 min walking, 10 min sitting) treadmill walking over 3 h in 35°C and 30% relative humidity. Subjects wore wildland firefighter flame-resistant meta-aramid blend pants and shirt with either a 100% cotton (C) or flame-retardant modacrylic undergarment (S), while carrying a 16-kg pack, helmet and leather gloves. Exercise was followed by a 30-min rest period without pack, helmet, gloves, and outerwear shirt. Rectal temperature and physiological strain were greater in S than C (P = 0.04). No significant differences were found for heart rate, rating of perceived exertion, energy expenditure or skin temperature between C and S. Skin blood flow increased significantly in S following the second hour of exercise, resulting in a time × trial interaction (P = 0.001). No significant differences for skin blood flow were found post exercise. Sweat rate and percent dehydration were not different between C and S. These data indicate that, of the two undergarments investigated, the synthetic undergarment negatively affected physiological factors that have been shown to indicate an increased risk of heat-related injuries.

Original languageEnglish
Pages (from-to)275-281
Number of pages7
JournalInternational Journal of Wildland Fire
Issue number4
StatePublished - 2019


  • heat-related injuries
  • physiological strain index
  • skin blood flow
  • wildland firefighters


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