The ability to repeatedly perform high-intensity efforts interspersed with minimal recovery, coupled with optimal cognitive function, is imperative for successful team-sport performance (Spencer, Bishop, Dawson & Goodman, 2012; Williams, 2000). However, both components face impairment when core temperatures reach 38.5°C, which can commonly occur in hot environments (Drust, Rasmussen, Mohr, Nielsen & Nybo, 2005; Schmit, Hausswirth, Le Meur & Duffield, 2017). Therefore, the present study investigated the effect of internal and external cooling on high intensity intermittent cycling performance and cognitive function in the heat.
Twenty-nine male, games players completed a control (CON) and cooling trial (ice slurry & ice collar; COOL) in the heat (33°C, 50% RH) involving a 40-min intermittent cycling protocol consisting of 2 sets of 10 2-min stages (5-s sprint, 105-s active recovery, 10-s rest). Participants completed a battery of cognitive tests, which involved the Visual Search test, Stoop Task, Sternberg Paradigm and RVIP, pre- and post-exercise with physiological and perceptual responses recorded throughout. All data was analysed using a two-way repeated measures ANOVA.
No differences in peak or mean power output were found between conditions (all p > 0.05). Rectal (COOL: 37.39 ± 0.59; CON: 37.59 ± 0.56°C, p < 0.001) and neck (COOL: 28.87 ± 4.87; CON: 32.82 ± 1.43°C, p < 0.001) temperature, as well as heart rate (COOL: 123 ± 40; CON: 127 ± 41 beats.min-1, p = 0.038), were found to be lower in COOL. Participants reported feeling better in COOL as well as reporting lower ratings of thermal sensation (p < 0.001) and improved comfort (p < 0.001). Response times on the number level of the Sternberg Paradigm were quicker during COOL (COOL: 434 ± 77 ms; CON: 437 ± 84 ms, p = 0.045) however, over time, the improvement in response times was greater in CON (COOL: 6 ± 3ms quicker; CON: 26 ± 2ms quicker, p = 0.015). Response times got quicker over time to a greater extent in CON on the Visual Search complex level (COOL: 15 ± 1ms quicker; CON: 119 ± 31ms quicker, p = 0.009). Stroop Task complex level response times were quicker over time in COOL compared to CON (COOL: 48 ± 23ms quicker; CON: 11 ± 18ms quicker, p = 0.002). However, no differences were found on the other tests or test levels, or for accuracy of responses (all p > 0.05).
The combined cooling intervention led to improvements in some physiological and perceptual responses to intermittent exercise in the heat and minimally influenced cognitive function, as seen through enhanced executive function on the Stroop Task. However, the combined cooling intervention did not affect intermittent sprint performance, which was evidenced through a lack of differences in peak or mean power output. These findings provide information on a practical combined cooling method that can be feasibly implemented in elite sport.