Intracellular and Extracellular Water Content With Carbohydrate-Loading Diets

Abstract

Introduction: In prolonged physical activities, water replacement and muscle glycogen content are limiting factors in marathon runners. Carbohydrate-loading (CHO) in the days prior to endurance competition is a commonly employed method to optimise muscle glycogen stores and optimise exercise performance. Since each gram of muscle glycogen binds ∼2.7-4 grams of water, water retention may occur during carbohydrate-loading diets. Objective: To evaluate differences between CHO loading strategies (Bergström and Sherman) on intracellular (ICW) and extracellular (ECW) water content. Methods: Twenty-three runners were randomly allocated to two interventions (Bergström and Sherman) in a crossover design. Participants underwent a baseline evaluation before 3 days of glycogen depletion followed by 3 days of carbohydrate loading with a washout of 30 days consisting of normal diet and training. Multifrequency bioimpedance (BIS) was used to assess ICW and ECW at Baseline, Post-depletion and Post-CHO to determine any differences between Bergström and Sherman protocols. Blood samples were also obtained to assess potassium levels. Associations between ICW and ECW and muscle glycogen were determined. Results: There were no differences in ICW or ECW content between the two interventions at any moment. There was an effect of time for ICW, with an increase from Post-depletion to Post-CHO without any difference between interventions. Plasma potassium decreased from Baseline to Post-depletion in both conditions. There was no difference in muscle glycogen content between interventions or moments. Conclusion: There were no differences in ICW and ECW content between the Bergström and Sherman interventions at any moment. Level of Evidence I; Tests of Previously Developed Diagnostic Criteria.