Francisco Javier Martínez-Noguera, Alessio Cabizosu, Pedro E Alcaraz, Cristian Marín-Pagán
Journal: Journal of the International Society of Sports Nutrition 2024;21(1):2346563
PMID: 38676933
Global sports competitions are commonly held in summer, exposing athletes to temperatures in the high 20˚C/low 30˚Cs, inducing thermoregulatory stresses which may affect performance and health. Glycerol prior to exercise induces hyperhydration which may counteract the effects of high temperatures and can also be converted to glucose. The aim of this randomised, placebo-controlled crossover trial was to evaluate the effects of glycerol prior to a rectangular treadmill test on dehydration, rate of perceived exertion (RPE), heart rate, metabolic, kinematic, and thermographic variables in 8 international race walkers at 28.1-28.3 ˚C and relative humidity of 31.4-31.5%. Athletes took 1g/kg bodyweight (bw) glycerol in 26 ml/kg bw flavoured water or the same amount of flavoured water 2 hours prior to the exercise test. There were no statistically significant differences in any parameters between groups except for body mass which was more favourable in the placebo group, with athletes losing more weight after the glycerol than the placebo. The authors conclude that under the chosen conditions, glycerol supplementation did not show any benefits and speculate that the chosen temperature and humidity may have not induced sufficient thermogenic stress to generate a difference.
BACKGROUND
Due to the increase in global temperature, it is necessary to investigate solutions so that athletes competing in hot conditions can perform in optimal conditions avoiding loss of performance and health problems. Therefore, this study aims to evaluate the effect of pre-exercise glycerol supplementation during a rectangular test at ambient temperature mid (28.2ºC) on dehydration variables in international race walkers.
METHODS
Eight international male race walkers (age: 28.0 years (4.4); weight: 65.6 kg (6.6); height: 180.0 cm (5.0); fat mass: 6.72% (0.66); muscle mass: 33.3 kg (3.3); VO: 66.5 ml · kg·min (1.9)) completed this randomized crossover design clinical trial. Subjects underwent two interventions: they consumed placebo ( = 8) and glycerol ( = 8) acutely, before a rectangular test where dehydration, RPE, metabolic, kinematic, and thermographic variables were analyzed before, during and after the test.
RESULTS
After the intervention, significant differences were found between groups in body mass in favor of the placebo (Placebo: -2.23 kg vs Glycerol: -2.48 kg; = 0.033). For other variables, no significant differences were found.
CONCLUSION
Therefore, pre-exercise glycerol supplementation was not able to improve any dehydration, metabolic, kinematic, or thermographic variables during a rectangular test at temperature mid in international race walkers. Possibly, a higher environmental temperature could have generated a higher metabolic and thermoregulatory stress, generating differences between groups like other previous scientific evidence.
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