Novel During-event Cooling Wearable Effects on Thermoregulation, Cognition and Running Performance in the Heat

Jacobs, Lucy
Kilding, Andrew
Casadio, Julia
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Master of Sport and Exercise
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Exercise in the heat causes thermoregulatory and physiological strain, impairs cognitive function and reduces exercise capacity. Consequently, performing in hot and humid environments presents multiple challenges for athletes. Several strategies have been proposed to combat the negative effects of heat stress on sport performance including acclimatisation, acclimation and cooling. With regards to cooling, the use of light-weight cooling wearables prior to (pre-cooling), or during exercise (per-cooling) can facilitate reduced heat storage and enhanced heat loss for improved exercise performance. Indeed, neck and/or hand cooling has been proposed as an accessible, effective method to target areas of high thermal sensitivity and vasodilatory power through attenuation of increased body temperature during exercise. However, limited research has investigated neck and hand per-cooling wearables during exercise, and even further limited in addition to ice-vest pre-cooling.

Aims: To determine and compare 1) the effects of hand, neck and torso cooling on thermoregulatory, cardiovascular, perceptual and cognitive responses to exercise in the heat; and 2) the effects of hand, neck and torso per-cooling on running performance in the heat.

Methods: Seven runners and triathletes (four male, three female) participated (within subjects, counterbalanced design) and performed a familiarization session, followed by four experimental sessions separated by at least five days. All four exercise trials were conducted in an environmental chamber (35°C, 75% relative humidity (RH)) during which participants completed 30 minutes of passive pre-cooling (PC, with or without an ice-vest), followed by a 40 minute RPE 12 clamped steady state (SS) run and 3km treadmill time trial (TT) during which participants were provided with four different cooling combinations including: ice-vest pre-cooling only (V), ice-vest pre-cooling, hand and neck cooling during exercise (VHN), hand and neck cooling alone during exercise (HN) and neck cooling alone during exercise (N). Core temperature (Tc) , Mean skin temperature (MST), Neck skin temperature (Tneck), hand skin temperature (Thand), heart rate (HR), rating of perceived exertion (RPE), thermal comfort (TC) and thermal sensation (TS) were measured. Participants also completed two identical cognitive tests (Corsi Block Test), (Go-No/Go Test) during the session.

Results: 3km TT performance was significantly faster with VHN, HN and N versus V (813s, 849s, 847s vs. 908s, p<0.05). Core temperature (Tc) was not altered by any cooling intervention at any protocol phase. Mean skin temperature (MST) was coolest in V (p<0.001) during PC but highest through SS and TT phases (p<0.001). During SS, HN had lower heart rate (HR) and MST than N alone (p<0.001). Change in TS during SS was greater for V (p=0.036, 1.93 ± 0.78) than HN (p=0.024, 1.07 ± 0.67) and VHN (p=0.036, 1.14 ± 0.79). Similarly, TC ratings were also higher for V (3.07 ± 1.7) than HN (p=0.004, 1.28 ± 1.3) and VHN (p=0.04, 1.85 ± 1.4). In TT, heart rate was significantly higher in N versus all other conditions (p<0.05). There were no differences between conditions for Corsi Block test and Go-No/Go errors. The Go-No/Go reaction time during the Post PC phase was slower in VHN than HN (p=0.01, g = 1.09).

Conclusion: Novel hand and neck per-cooling wearables combined with ice vest pre-cooling had a positive effect on endurance running performance over a 3km TT. The novel neck scarf and hand cooling pouch did not impact HR, Tc, working memory or reaction time however they did induce significant skin temperature reductions for the cooled area and positively impacted perceptual measures of thermal comfort and sensation, supporting the notion of wearable multi-site cooling for endurance running in the heat.

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