Carbohydrate Oxidation in Elite Wheelchair Racers During Marathon Simulation

Dietary Carbohydrate, Para-Athletes

To examine the effect of varying amounts of carbohydrate ingestion on performance, gastrointestinal experiences, and other physiological markers in elite wheelchair racers during a simulated marathon.

The metabolic demands created by endurance activities, which include muscle and liver glycogen depletion as well as losses in body fluids and electrolytes, are significant limitations to the performance potential of the athlete. For this reason, a well-supported recommendation exists for such athletes to consume a carbohydrate (CHO) formula, in particular, one containing electrolytes during their activity. Furthermore, the current CHO recommendations to support prolonged activity have been developed specifically for able-bodied athletes, thus are potentially inappropriate for para athletes. Metabolic and physiological functions are altered in individuals with physical disabilities, so it is unknown how transferable these recommendations are to para athletes. As such, it is important to understand this population's unique carbohydrate requirements for performance optimization. Recently, our group showed stable elevated circulating glucose concentrations by utilizing two different sources of CHO dosed at 60 g/h when compared to water. Significantly improved performance was observed with both CHO conditions. These findings, combined with studies showing decreased net muscle glycogen degradation during intravenous glucose infusion (3.5 g/min), show the importance of plasma glucose concentration for sustained performance. Therefore, the purpose of this study is to investigate the SCI-specific responses to exogenous CHO during a full marathon simulation (MS). Twelve highly trained men and women (20-50 yrs old) will be recruited to the study. The inclusion criteria are: 1.) Best marathon time lower than 2h 2.) and ≥6 months of prior training history. After initial screenings, participants will perform three marathon (MS) trials. In cross-over trials, each subject will participate in a MS trial consisting of a challenge (90% of subject's best marathon time) followed by a time trial (TT) representing the last 10% of the marathon time. During each MS trial, participants will be randomly assigned to receive either water, 30g, or 60g of carbohydrate (CHO) every 15 minutes in the form of a sports nutrition beverage. Repeated blood and breath sampling will occur throughout the MS. These samples will be used to determine glucose concentration, lactate concentration, as well as CHO and fat oxidation. Heart rate, core temperature, blood pressure, ratings of perceived exertion and GI symptoms will also be assessed throughout the MS and after the time trial. Completion of this research study will help to identify more appropriate CHO recommendations for para athletes to support prolonged endurance exercise. This will aid in the understanding of the unique physiological and metabolic needs of para athletes as compared to their able-bodied counterparts, thus enhancing inclusivity within sports nutrition literature.

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