Optimization of post-exercise recovery beverages’ composition

Fluid intake and adequate hydration are essential and critical during and after training sessions and competition events. Reductions in body water content will prejudice performance with exercise performance significantly impaired when 2% or more of body weight is lost through sweat [1-3]. Guidelines states that in the post exercise (within 30 minutes to 1 hour after the end of the physical exercise), effective rehydration requires the intake of a volume of fluid equal to, at least, the 150% of the difference between body weight before and after the training [4] but a lack is still present regarding specific guidelines related to beverage formulations, strategies and volumes.
\nIndeed, in addition to water, sweat contains variable amounts of sodium, with lesser amounts of potassium, calcium, and magnesium so it is important that athletes can benefit from intake of an appropriate amount of a well-formulated drink [5-9]. 
\nOur prevoius studies underlined the potential role of skimmed milk as post recovery drink possibly linked to its specific characteristics [10-12]. In particular, milk has naturally high concentrations of electrolytes, that should aid in fluid recovery following exercise [4, 13].
\nMoreover, it contains casein and whey proteins in a ratio of 3:1 which provides for slower digestion and absorption of these proteins resulting in sustained elevations of blood amino acid concentrations.
\nIn this regard, the aim of this study was to further evaluate the role of milk as post-recovery beverage. In particular, skimmed milk was tested in different volumes (no diluted skimmed milk, skimmed milk diluted 1:2 and 1:3) in order to better evaluate its role and to optimize volume. Moreover, specific nutrients (i.e. Casein, Sodium) and their possible combinations (Casein + Sodium, Whey proteins + Sodium) were taken into account in different concentrations to investigate possible role of specific nutrients. 
\n30 athletes, both male and female, aged between 19 and 47, took part to the study. Each strategy was tested for one week with an intake equal to 500ml of the specific drink with the addiction of an amount of water equal to the volume needed to reach the 150% of loss body weight during the exercise.
\nA specific questionnaire was performed to ask about type of activity performed, the intensity of the activity, the urine colour, the thirst sensation after waking up in the morning; eventual cramps. Anthropometric measurement and Bioimpedence Analysis (both mono-frequency and multi-frequency) were performed to assess body composition and hydration in term of total body water, intra-cellular water and extra-cellular water.
\nFollowing guidelines indications, through the use of 150% of water intake in the post exercise, a variability among subjects were observed with cases also of worsening of hydration status underlining the importance of beverage characteristics as several elements might affect fluid balance: the macronutrient content, the electrolyte (i.e. sodium and potassium) [5-9].
\nAmong the different strategies tested, skimmed milk resulted again the best one, able both to improve total body water in terms of intra-cellular water and body composition more than single milk nutrients. This underlines the importance of further investigate milk as post-exercise recovery beverage in terms not only of nutrients content but also nutrients synergism.
\nEven if data obtained by this study are limited by the restricted number of athletes, obtained results can be considered a step ahead to better evaluate the role of milk as recovery beverages, to define its applicability and to study new hydration protocols in order to improve the present knowledge on athlete’s hydration and recovery. 
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\nReferences
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\n[10]\tVici G, Albertini F, Quintavalle A, Belli L, Polzonetti V. Milk as recovery drink after exercise: a case study. Alimenti Funzionali e Nutraceutici per la Salute. Camerino, 28th June 2016
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\n[13]\tRoy BD. Milk: the new sports drink? A Review. J Int Soc Sports Nutr. 2008;5:15.

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