Cardiovascular and thermoregulatory responses to treadmill running while wearing shirts with different fabric composition

Clothing must be worn in many athletic and occupational situations as part of a uniform or for protection from the environment, but clothing interferes with sweat evaporation and heat dissipation. Thus, the heat dissipation qualities of clothing worm by athletes, soldiers, and others working and/or competing at moderate to high workloads is important. The purpose of this study was to determine if a synthetic shirt purported by the manufacturer to be advantageous in dissipating heat permits more effective heat dissipation than a cotton shirt during exercise in a temperate environment. Methods: Nine active males ran on a treadmill at 65% VO2peak for 45 min in 22 degrees C while wearing cotton sweatpants and either a long-sleeve synthetic shirt (SS), cotton shirt (CS), or no shirt (NS). The first and second trials were counterbalanced, and the third trial was determined by default. At least one week lapsed between trials. Results (means +/- SD): There were no differences in RPE, VO2, change in rectal temperature (Delta T-re), or change in heart rate (Delta HR) between conditions (p > 0.05). Final T-re in SS (38.8 +/- 0.3 degrees C) was lower than CS (39.1 +/- 0.4 degrees C) but not different than NS (38.9 +/- 0.2 degrees C). Mean skin temperature was lower in NS than CS (p < 0.05). Total water loss was lowest in NS (1.1 +/- 0.3L, p < 0.05), while SS (1.4 +/- 0.3L) and CS (1.5 +/- 0.3L) were similar (p > 0.05). Thermal sensation was lower in SS and NS than CS. Conclusion: Wearing a synthetic shirt provides a limited thermoregulatory benefit compared to a standard cotton shirt, but comfort is enhanced.