The effect of a combined cooling intervention on cognitive function in the heat during an intermittent running protocol

Abstract

Despite optimal cognitive function being essential for performance, there is a lack of research on the effectiveness of combined cooling interventions on team sport athlete's cognitive function when exercising in the heat. In a randomised, crossover design, 12 unacclimatised men (age: 22.3 ± 3.0 years, body mass: 73.4 ± 5.1 kg, height: 181.0 ± 5.3 cm and $\dot{V}{O}_2$ max: 51.2 ± 9.5 mL/kg/min) participated in a control (CON) and combined cooling trial (ice slurry and ice collar; COOL). A battery of cognitive tests were completed prior to, during (at half-time) and following a 90-min intermittent running protocol in the heat (33°C, 50% relative humidity (RH)). Perceptual and physiological measures were taken throughout the protocol. In CON, response times were quicker on the Stroop task complex level (p = 0.002) and the visual search test complex level at full-time (p = 0.014) compared to COOL. During COOL, response times were quicker at half-time on the Stroop task complex level (p = 0.024) compared to CON. Lower rectal temperatures were seen during COOL (CON: 37.44 ± 0.65°C and COOL: 37.28 ± 0.68°C) as well as lower skin, neck and forehead temperatures (main effect of trial, all p < 0.05). Lower ratings of thermal sensation and perceived exertion and enhanced thermal comfort were recorded during COOL (main effect of trial, all p < 0.05). Whilst minimal differences in cognitive function were found when using the combined cooling intervention, the findings highlight a practical and effective strategy to improving many physiological and perceptual responses to intermittent exercise in the heat.

Keywords: football; ice slurry; neck cooling; soccer; team sports.

FIGURE 1

Schematic of the main trial protocol. Key: CF Full, full battery of cognitive function tests; CF Short–short battery of cognitive function tests; FSITP, intermittent running protocol; DB–drink break; HT, half‐time; RPE, rate of perceived exertion; TS, thermal sensation; TC, thermal comfort; FS, feeling scale; FAS, felt arousal scale; T_rec, rectal temperature; T_forehead, forehead temperature; T_chest, chest temperature; T_forearm, forearm temperature; T_thigh, thigh temperature; T_calf, calf temperature; T_neck, neck temperature and HR, heart rate.

FIGURE 2

Rectal (A), skin (B), neck (C) and forehead (D) temperature during the control and cooling trials (mean ± SD). Rectal temperature, main effect of trial: p = 0.031 and d = 0.24; trial × time interaction: p = 0.049; skin temperature, main effect of trial: p < 0.001 and d = 0.31; trial × time interaction: p < 0.001; neck temperature main, effect of trial: p < 0.001 and d = 0.97; trial × time interaction: p < 0.001; forehead temperature, main effect of trial: p = 0.042 and d = 0.19; trial × time interaction: p = 0.204. Key: PC, pre‐cool; 1st EXC, first half of exercise; HT, half‐time; 2nd EXC, second half of exercise and DB, drinks break. Significant pairwise comparisons are denoted by *.

FIGURE 3

Ratings of thermal sensation (A) and thermal comfort (B) during the control and cooling trials (mean ± SD). Thermal sensation, main effect of trial: p = 0.007 and d = 0.39; trial × time interaction: p = 0.002; thermal comfort, main effect of trial: p = 0.002 and d = 0.37; trial × time interaction: p < 0.001. Key: PC, pre‐cool; 1st EXC, first half of exercise; HT, half‐time; 2nd EXC, second half of exercise and DB–drinks break. Significant pairwise comparisons are denoted by *.

FIGURE 4

Ratings of perceived exertion (A) and heart rate (B) during the control and cooling trials (mean ± SD). Rating of perceived exertion, main effect of trial: p = 0.026 and d = 0.15; trial × time interaction: p = 0.142; Heart rate, main effect of trial: p = 0.558 and d = 0.02; trial × time interaction: p = 0.835. Key: PC, pre‐cool; 1st EXC, first half of exercise; HT, half‐time; 2nd EXC, second half of exercise and DB, drinks break.