Wearing a breathable T-shirt does not affect thermoregulatory responses during exercise under hot conditions

Sweat absorbed by clothing forms a moisture film on fabric surfaces, reducing fabric breathability and disrupting thermoregulation during exercise in a hot environment. We investigated whether T-shirts made from a newly developed fabric with hydrophobic and water-repellent fibers near the through holes could prevent sweat film formation, thereby enhancing intraclothing microclimate and thermoregulatory responses. Thirteen male runners completed 30-min treadmill sessions at moderate and high intensities while wearing either the new fabric T-shirt (Dry Aeroflow, DAF) or a polyester T-shirt (CONT) at an ambient temperature of 32°C and a relative humidity of 50% with an air velocity of 0.8 m/s. Compared with CONT, intraclothing humidity was decreased on the chest and back, and chest but not back skin temperature was decreased by 2°C in DAF. However, thermoregulatory key variables such as rectal temperature, mean skin temperature, sweat rates, and heart rate did not differ between the T-shirts. We concluded that the a T-shirt with enhanced breathability does not affect overall thermoregulatory response during exercise in the heat despite the partial improvements in intraclothing microclimate and in reducing local skin temperature.