Introduction: Participation in ultra-endurance events has increased exponentially in recent years. Despite this, performance in such demanding events has been stagnant. Numerous studies have observed that ultra-endurance athletes consistently fail to meet the extensive energy demands and the current carbohydrate (CHO) recommendations, which may in part explain this plateau in performance. To date, little is known about the causes of suboptimal energy and CHO intake or the most effective strategies to address these inadequacies. Therefore, the aims of this thesis were to (i) explore the challenges to optimal nutritional intake, (ii) establish whether a gut-training programme could enable ultra-endurance athletes to meet the CHO recommendations and (iii) determine whether a short term high fat, low CHO diet (HFLC) or a low fat, high CHO (LFHC) diet prior to competition is more effective for ultra-endurance performance, when fuel availability is likely to be compromised. Methods: One hundred and seventy participants took part in the studies involved in this thesis, including 118 ultra-endurance athletes. The remaining participants consisted of three population groups with different levels of nutrition knowledge and experienced distance athletes, who were involved in the developmental phase of the first two studies. Both studies employed a two-phase approach to (i) adapt and evaluate a questionnaire for use with ultra-endurance athletes; and (ii) subsequently implement the questionnaire with these athletes (n = 101). The first questionnaire was completed alongside a series of 24 hr food diaries to explore the relationship between nutrition knowledge and food intake. The second explored the main factors that influence food choices during training and competition. The penultimate study required ultra-runners (n = 17) to follow a multicomponent dietary intervention (gut training + HFLC compared with gut training + LFHC diet), which was designed to overcome identified challenges to optimal nutritional intake and to optimise fuel iii availability in preparation for a 56 km ultra-endurance foot race. The final study explored the experiences of a subsample of ultra-endurance runners (n = 14) as they made their food choices during the race, using a series of face-to-face interviews. Results and discussion: The nutrition knowledge of ultra-endurance athletes was superior to the general population, however there was no relationship between knowledge and the adequacy of the ultra-endurance athletes diet. The most important factors that influenced the food choices of these ultra-endurance athletes were the avoidance of gastrointestinal symptoms (GIS) and the provision of adequate energy. These factors were followed closely by the desire for nutritious products and those that were easy to consume during training and competition. The multicomponent intervention successfully manipulated the CHO and fat composition of the 17 ultra-endurance athletes, however this did not affect their race performance. Furthermore, despite a period of gut training designed to improve the ultra-runners tolerance of high volumes of CHO, ultra-runners failed to meet the recommended rate of CHO intake and the severity of their GIS did not improve. Subsequent analysis of the interviews indicated that the processes involved in making food choices during the race were complex and dynamic. All ultra-runners altered their food choices during the race in response to triggers, such as hunger and taste fatigue. This resulted in the consumption of lower CHO density products, which may partially explain the suboptimal CHO intake. Conclusion: Advances in ultra-endurance performance appear to be restricted in part by the adequacy of the athlete’s nutritional intake. At present, strategies to address the multiple challenges to optimal nutritional intake have had limited success. However, practicing competition nutrition during training is likely to simplify iv the decision-making process during events, allowing ultra-endurance athletes to focus on their performance.
|Date of Award||23 Aug 2018|
|Supervisor||Andy Sparks (Director of Studies) & LARS MCNAUGHTON (Supervisor)|
- food choice