Nutritional strategies for endurance and ultra-endurance cycling
Doctoral Thesis
2008
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University of Cape Town
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Abstract
Ingestion of a high carbohydrate (CHO) diet (7-10 g CHO/kg body mass) for 3 days, typically referred to as ‘CHO-loading’, is a commonly recommended dietary practice for endurance sporting events lasting >90 minutes. CHOloading effectively maximizes muscle glycogen stores and has been shown to enhance prolonged exercise performance. However, the body’s glycogen stores are limited, therefore a dietary strategy that would not only increase CHO availability but also ‘spare’ muscle glycogen during exercise may be more beneficial during prolonged exercise compared to a standard CHO-loading diet. Preliminary studies in which athletes ingested a high fat diet (4-4.6 g fat/kg body mass) for 5-6 days followed by 1 day of CHO-loading have been shown to increase fat oxidation and ‘spare’ muscle glycogen during prolonged exercise compared to a high CHO diet. However, the effectiveness of a high fat diet followed by CHO-loading has not been tested in self-paced endurance and ultra-endurance events. Further, there is little available evidence concerning the pre-event habitual dietary practices of ultra-endurance athletes. It is possible that athletes and cyclists competing in endurance and ultra-endurance events have diets which may differ in macronutrient content compared to that typically recommended for endurance events. As a result, athletes may not respond in a similar way to diets typically recommended for endurance and ultra-endurance events, such as CHO-loading. The aims of this thesis were therefore: (1) to characterize the habitual dietary intakes of sub-elite male cyclists before and during an ultra-endurance event; (2) to investigate the effects of different dietary strategies aimed at increasing carbohydrate availability and ‘sparing’ muscle glycogen (e.g. CHO-loading and fat-adaptation), on substrate utilization and exercise performance during simulated endurance and ultra-endurance exercise; and (3) to investigate the individual responsiveness of athletes to these dietary strategies.
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Haveman, L. 2008. Nutritional strategies for endurance and ultra-endurance cycling. University of Cape Town.