Effect of internal and external cooling on high-intensity intermittent cycling performance and cognitive function in the heat.

We investigated the effect of internal and external cooling on high-intensity intermittent cycling performance and cognitive function in the heat. Twenty-nine males completed a control trial (CON) and a cooling trial (ice slurry and ice collar; COOL) in the heat (33°C, 50% relative humidity) involving a 40 min intermittent cycling protocol (two sets of ten 2 min stages, each consisting of 5 s sprint, 105 s active recovery and 10 s rest). A battery of cognitive tests was completed pre- and postexercise, with physiological and perceptual responses recorded throughout. No differences in peak or mean power output were found between conditions (all p > 0.05). Average trial rectal (COOL: 37.39°C ± 0.59°C; CON: 37.59°C ± 0.56°C, p < 0.001) and neck (COOL: 28.87°C ± 4.87°C; CON: 32.82°C ± 1.43°C, P < 0.001) temperatures were found to be lower in COOL. Participants reported feeling better and reported lower ratings of thermal sensation and improved comfort in COOL (all p < 0.05). Response times on the Stroop task complex level were quicker over time in COOL (COOL: -48 ± 23 ms; CON: -11 ± 18 ms, p = 0.002) and quicker overall on the number level of Sternberg during COOL (COOL: 434 ± 77 ms; CON: 437 ± 84 ms, p = 0.046). However, over time, the improvement in response times on the number level of Sternberg was greater in CON (COOL: -6 ± 3 ms; CON: -26 ± 2 ms, p = 0.015). Response times became quicker over time to a greater extent in CON on the visual search complex level (COOL: -15 ± 1 ms; CON: -119 ± 31 ms, p = 0.009). The combined cooling intervention did not influence sprint performance and had only a minimal influence on some domains of cognitive function but did lead to improvements in physiological and perceptual responses. These findings provide information on a practical combined cooling method that can be implemented in elite sport.