Glycerol-induced hyperhydration: A method for estimating the optimal load of fluid to be ingested before exercise to maximize endurance performance

McGill Nutrition and Food Science Centre, McGill University Health Centre, Royal Victoria Hospital, Montréal, Québec, Canada.
The Journal of Strength and Conditioning Research (Impact Factor: 2.08). 11/2009; 24(1):74-8. DOI: 10.1519/JSC.0b013e3181bd43e2
Source: PubMed


Glycerol-induced hyperhydration (GIH) has been shown to increase endurance performance (EP). However, EP starts declining at a dehydration level >2% body weight (BW). It thus appears that the use of GIH is only required when athletes anticipate that their fluid intake during exercise would not be sufficient to prevent a loss of BW >2%. In such a scenario, the optimal GIH load to be ingested before exercise would correspond to the amount of fluid that cannot be drunk during exercise and that would be just sufficient to keep the dehydration level <2% BW. No method exists enabling the estimation of the most optimal GIH load to be drunk before exercise to optimize EP. Here, such a method comprising 3 easy steps is presented. Step 1 provides a formula allowing users to determine relative exercise-induced dehydration level based on individual BW, exercise time, and estimated hourly sweat rate and fluid consumption during exercise. Step 2 takes into account the result of step 1 and provides a formula allowing determination of the minimal GIH load required before exercise to prevent a loss of BW >2%. Step 3 consists of identifying, among those pre-selected, a GIH protocol that increases body water by at least the amount computed in step 2. This method will remove much of the guess work involved in the decision-making process of the optimal amount of GIH that should be ingested before exercise by athletes for maximizing EP and will serve as a practical reference tool for all athletes using, and coaches, practitioners, and exercise physiologists recommending the utilization of, GIH as an ergogenic aid.

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Available from: Eric D B Goulet, Jan 18, 2015
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    ABSTRACT: The needs of water and electrolytes are quite variants, depending on age, physiological or environmental conditions. In most long-term sports, usual weight loss of 3-6%, affect in athletic performance. The effects of a 6% dehydration could be improved with individualized diet-specific nutritional strategies and allow only a 2-3% dehydration, which affect metabolic efficiency but will not risk the health. On the contrary, hyperhydration can be dangerous and is associated with hyponatremia that can cause cerebral edema or respiratory failure. Sports drinks should moisturize, providing minerals and carbohydrates and increase the absorption of water by an ideal combination of salts and sugars. Therefore, it is important to provide correct hydration -protocols before, during and after physical activity, as well as know possible limitations of the sport.
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