Acceptance of isotonic and hypotonic rehydrating beverages by athletes during training

This study compared the acceptance of two beverages (5% carbohydrate) of distinct osmolarities (hypotonic, 180 mOsm/kg and isotonic, 295 mOsm/kg) during the usual training practice of 97 athletes. A quantitative sensory profile by independent tasters ensured that organoleptic recognition would be unlikely during the tests. Each drink was consumed ad libitum during 3 different training sessions, at home. At each session, a subjective appreciation of hedonic and post-ingestive physiological effects (6 criteria) was obtained by means of a questionnaire. At the end of the experiment, the athletes were asked to express a preference for one of the "six" drinks. More athletes (blindly) chose the isotonic compared to the hypotonic drink (p = 0.03). This difference was not due intrinsically to the drinks, which the subjects were unable to distinguish on any of the criteria, but was related to certain aspects of the consumer's characteristics. Both groups had different drinking practices: the subjects choosing the isotonic beverage drank less before (p = 0.001) and more during (p = 0.013) the exercise. Age, sex, dimensions or type of physical activity (i.e. endurance vs speed/strength disciplines) were unrelated to the preference, except perhaps the duration of habitual exercise (p less than 0.05). We concluded that athletes, although unable to distinguish a hypotonic from an isotonic drink, may have specific habits and/or personal characteristics prompting them to favour one of them.