Environmental heat stress poses significant physiological challenge and impairs exercise performance. We investigated the impact of wrist percooling on running performance and physiological and perceptual responses in the heat. In a counterbalanced design, 13 trained males (33 +/- 9 years, 15 +/- 7% body fat, and maximal oxygen consumption, VO(2)max 59 +/- 5 mL/kg/min) completed three 10 km running time trials (27 degrees C, 60% relative humidity) while wearing two cooling bands: (1) both bands were off (off/off), (2) one band on (off/on), (3) both bands on (on/on). Heart rate (HR), HR variability (HRV), mean arterial pressure (MAP), core temperature (T(CO)), thermal sensation (TS), and fatigue (VAS) were recorded at baseline and recovery, while running speed (RS) and rating of perceived exertion (RPE) were collected during the 10 km. Wrist cooling had no effect (p > 0.05) at rest, except modestly increased HR (3-5 鈭哹eats/min, p < 0.05). Wrist percooling increased (p < 0.05) RS (0.25 鈭唌i/h) and HR (5 鈭哹eats/min), but not T(CO) (鈭?0.3 degrees C), RPE, or TS. Given incomplete trials, the distance achieved at 16 min was not different between conditions (off/off 1.96 +/- 0.16 vs. off/on 1.98 +/- 0.19 vs. on/on 1.99 +/- 0.24 miles, p = 0.490). During recovery HRV, MAP, or fatigue were unaffected (p > 0.05). We demonstrate that wrist percooling elicited a faster running speed, though this coincides with increased HR; although, interestingly, sensations of effort and thermal comfort were unaffected, despite the faster speed and higher HR.