This study aimed to compare the simultaneous use of internal and external precooling methods with singular methods and their effect on repeated sprint cycling in hot/humid conditions. Twelve male team sport players completed four experimental conditions, initially involving a 30-min precooling period consisting of either a cooling jacket (J); ingestion of an ice slushy ice slushy; combination of cooling jacket and ice ingestion (J + ice slushy); or control (CONT). This was followed by 70 min of repeat sprint cycling (in~35°C, 60% relative humidity [RH]), consisting of 2 × 30-min halves, separated by a 10-min half-time period where the same cooling method was again used. Each half comprised 30 × 4 s maximal sprints on 60 s, interspersed with sub-maximal exercise at varying intensities. Total mean power and work performed were significantly higher (p = 0.02) in J + ice slushy (233.6 ± 31.4 W) compared to ice slushy (211.8 ± 34.5 kJ), while moderate effect sizes (ES: d = 0.67) suggested lower core temperatures (TC) in J + ice slushy (36.8 ± 0.3°C) compared to J (37.0 ± 0.3°C) and CONT (37.0 ± 0.3°C) following precooling. A moderate ES (d = 0.57) also indicated lower TC in J + ice slushy (38.2 ± 0.3) compared to ice slushy (38.4 ± 0.4°C) after half-time cooling. Change (Δ) in mean skin temperature over half-time cooling was significantly greater (p = 0.036) for J (1.0 ± 0.4°C) compared to ice slushy (0.5 ± 0.5°C), and ES (d = 0.5-1.10) also suggested a greater Δ for J compared to the other conditions. Sweat loss was significantly greater (p < 0.05) in ice slushy and J + ice slushy compared to J and CONT. In conclusion, a combination of (external and internal) body cooling techniques may enhance repeated sprint performance in the heat compared to individual cooling methods.
This study determined whether precooling would have an additive effect on repeat-sprint cycling performance in heat following partial acclimation. Ten males completed three trials; Pre Acclimation (Pre Acc) and two Post Acclimation trials, one with precooling (ice jacket and slushy; Post Acc +PC) and another without (Post Acc). Trials consisted of a 30-min baseline period followed by a 70-min repeat-sprint protocol in ∼35°C and 60% relative humidity. Separating pre and post trials were five heat acclimation sessions. Although no significant differences were found for performance variables, inferential statistical analysis resulted in moderate effect sizes, which suggested more work (J · kg(-1)) was performed in Post Acc compared with Pre Acc. Further, 'possible' and 'very likely' benefits were found for every performance variable for Post Acc compared with Pre Acc, while 'possible' benefits were found for Post Acc, compared with Post Acc +PC, for peak power output (W and W · kg(-1)). Moderate to strong effect sizes suggested lower core temperatures in both post acclimation trials compared with Pre Acc. Sweat loss was significantly higher (P < 0.05; 23.1%) in Post Acc +PC compared to other trials. In conclusion, no additional performance enhancement was seen when partially acclimated individuals precooled prior to repeat-sprint performance in heat.
This study compared the effects of a hand cooling glove (∼16°C water temperature; subatmospheric pressure of -40 mmHg) and a cooling jacket (CJ) on post-exercise cooling rates (gastrointestinal core temperature, Tc; skin temperature, Tsk) and cognitive performance (the Stroop Colour-Word test). Twelve male athletes performed four trials (within subjects, counterbalanced design) involving cycling at a workload equivalent to 75% ⩒Omax in heat (35.7 ± 0.2°C, 49.2 ± 2.6% RH) until a Tc of 39°C or exhaustion occurred. A 30-min cooling period (in 22.3 ± 0.3°C, 42.1 ± 3.6% RH) followed, where participants adopted either one-hand cooling (1H), two-hand cooling (2H), wore a CJ or no cooling (NC). No significant differences were seen in Tc and Tsk cooling rates between trials; however, moderate effect sizes (d = 0.50-0.76) suggested Tc cooling rates to be faster for 1H, 2H and CJ compared to NC after 5 min; 1H and CJ compared to NC after 10 min and for CJ to be faster than 2H at 25-30 min. Reaction times on the cognitive test were similar between all trials after the 30 min cooling/no-cooling period (p > .05). In conclusion, Tc cooling rates were faster with 1H and CJ during the first 10 min compared to NC, with minimal benefit associated with 2H cooling. Reaction time responses were not impacted by the use of the glove(s) or CJ.
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