Does wearing clothing made of a synthetic “cooling” fabric improve indoor cycle exercise endurance in trained athletes?

This randomized, double‐blind, crossover study examined the effects of a clothing ensemble made of a synthetic fabric promoted as having superior cooling properties ( COOL ) on exercise performance and its physiological and perceptual determinants during cycle exercise in ambient laboratory conditions that mimic environmental conditions of indoor training/sporting facilities. Twenty athletes (15 men:5 women) aged 25.8 ± 1.2 years (mean ±  SEM ) with a maximal rate of O 2 consumption of 63.7 ± 1.5  mL ·kg −1 ·min −1 completed cycle exercise testing at 85% of their maximal incremental power output to exhaustion while wearing an ensemble consisting of a fitted long‐sleeved shirt and full trousers made of either COOL or a synthetic control fabric ( CTRL ). Exercise endurance time was not different under COOL versus CTRL conditions: 12.38 ± 0.98 versus 11.75 ± 1.10 min, respectively ( P  > 0.05). Similarly, COOL had no effect on detailed thermoregulatory (skin and esophageal temperatures), cardiometabolic, ventilatory, and perceptual responses to exercise (all P  > 0.05). In conclusion, clothing made of a synthetic fabric with purported “cooling” properties did not improve high‐intensity cycle exercise endurance in trained athletes under ambient laboratory conditions that mimic the environmental conditions of indoor training/sporting facilities.