Multiple Transportable Carbohydrates and Endurance Exercise: Addressing Selected Issues in the Literature

Abstract

Over the last two decades, numerous studies have shown that feeding multiple saccharides during exercise--compared to a single saccharide--increases exogenous carbohydrate oxidation, reduces gastrointestinal distress, and improves performance when carbohydrate intake exceeds 50-60 g/hr. Glucose and fructose utilize separate intestinal transporters and have therefore been referred to in the literature as multiple transportable carbohydrates (MTC). Despite the growing evidence, few studies have examined MTC during running, and none of the previous studies assessed their effects on running stride parameters. Moreover, no published study has quantified MTC use in a non-simulated setting, and previous studies largely failed to include women, as only 17 of 266 participants from 24 studies have been female. This dissertation attempted to address these limitations using observational and experimental approaches. The findings from Chapter 3 suggest that many athletes do not consume a balanced mix of saccharides during ultra-endurance competition. This is likely due, in part, to the saccharide profiles found in many foods and beverages sold as carbohydrate supplements. This suggests that competitors may need more education regarding MTC and should pay close attention to the saccharide composition of the products they consume during competition. The findings from Chapters 4 and 5 markedly add to the literature examining MTC during endurance running. The results showed that ingestion of a glucose-fructose beverage (1.3 g/min carbohydrate)--compared to glucose-only--improved running performance and psychological affect, as well as reduced gastrointestinal distress. Performance benefits were apparent for men and women alike, and ranged from 1.6-2.6%. Additionally, ingestion of glucose-fructose better maintained stride frequency during 120 min of constant-velocity running. Thus, this dissertation contributes to the knowledge base of MTC in several ways. It contains the first data to show that MTC can enhance running performance, including for women. It also includes the first data to quantify MTC use during a "real-life" event. Finally, it provides a foundation for future studies attempting to examine the effects of MTC during running and under field-based environments.