The effect of dietary standardisation on exercise performance and physiological responses in male athletes
Sport scientists have been using different techniques to control dietary intake in an attempt to minimise the impact of several dietary components on the outcomes of the study. This is achieved by eliminating some components completely from the diet (such as caffeine and alcohol) for few days or controlling the intake by replicating what was consumed before the first trial, prior to every subsequent trial. Researchers help participants replicate their diet by using dietary standardisation tools such as dietary recall and food record or by providing pre-packaged meals (standardised diet). The aims of this PhD were 1) to assess the reproducibility of a diet using different standardisation techniques, 2) examine what effect does 24-hours carbohydrate manipulation within a 15% variation have on endurance capacity and physiological responses, 3) assess the new proposed method to standardise dietary intake, and 4) measure the efficacy of encouraging individuals to stay well-hydrated on next day hydration status. This PhD concluded that standardised diet is the best approach to control dietary intake. Dietary recall and food record techniques should only be used when large effect is expected and the diet has low impact on the intervention. The liquid based standardised diet that we proposed was found to be an effective technique with similar reproducibility to solid based standardised diet (2-3% and 5% variation, respectively, in energy and macronutrient intakes). Furthermore, it was suggested that a 15% difference in 24-hour carbohydrate intake did not significantly affect endurance capacity, nutrient oxidation and blood glucose/lactate levels in trained cyclists. Finally, it was confirmed that encouraging participants to drink water in the pre-trial preparation period is not enough to achieve euhydration before exercise tests. This PhD adds essential information to the area of dietary standardisation and helps improve the quality of future research projects.
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