Author(s): BOOTH, P., Institution: LEEDS BECKETT UNIVERSITY, Country: UNITED KINGDOM, Abstract-ID: 2587

INTRODUCTION:
Ultra-running is in the midst of a carbohydrate (CHO) revolution. Anecdotal reports by ultra-runners suggest CHO ingestion at 120 g/h significantly enhances performance compared to the current recommended dose of 90 g/h. However, CHO dose-response studies have yet to establish a performance advantage of 120 g/h over 90 g/h. This is the first study to evaluate the effects of ingesting 120 g/h vs 90 g/h of CHO on ultra-running performance, heart rate, rating of perceived exertion (RPE), blood glucose, blood lactate, and gastrointestinal distress in ultra-runners during a mountain trail ultra-marathon.
METHODS:
28 male (n=18) and female (n=10) ultra-runners were recruited, however only 10 males completed the study. On two occasions, separated by 21 days, participants completed three 17.7 km loops of a simulated 53 km mountain trail race with 2,500m of vertical elevation. Participants were blinded to dose, taking either 90 or 120 g/h (maltodextrin: fructose ratio 1:0.8) in a randomised crossover design. CHO were provided as gels and drinks, consumed in 30 or 40 g doses every 20 minutes throughout the race. Race times were recorded at the end of each loop and at three separate checkpoints within each loop. RPE, gastrointestinal (GI) symptoms, blood lactate and glucose were collected pre-race and at the end of each loop, while heart rate was monitored throughout the study.
RESULTS:
There were no significant differences for total race completion time (p = 0.80), loop time (p = 0.80), or segment times (p = 0.79) between 90 and 120 g/h conditions. No significant differences were reported between conditions for GI symptoms during loop 1 (p = 0.98) and loop 2 (p = 0.87). GI symptoms steadily increased during loop 3 and were significantly greater in the 120 compared to the 90 g/h condition (16.8 vs 7.5; p = 0.035). During loop 3, upper GI symptoms accounted for 63% of all reported issues, which were significantly higher for the 120 g/h condition (9.0 vs 3.8; p = 0.013). Blood lactate did not change significantly with duration (p = 0.11). Blood glucose (p = 0.001), heart rate (p <0.0001), %VO2max (p <0.0001), and RPE (p <0.0001) all increased significantly with duration. There were no significant differences in these variables between conditions, except blood glucose and RPE, which were significantly higher in the 120 g/h condition during loop 3 (6.91 vs 6.20 mmol/l; p = 0.04 and 15.5 vs 14.5; p = 0.003, respectively).
CONCLUSION:
This is the first study to report that ingesting carbohydrates at a dose of 120 g/h does not improve performance during a 53 km mountain trail ultra-marathon compared with 90 g/h. This is despite an increase in upper gastrointestinal symptoms and perceived exertion during the final stage of the race whilst consuming 120 g/h of carbohydrates. Therefore, ultra-runners competing in trail races up to 50 km are recommended to follow current carbohydrate recommendations at 90 g/h, to avoid unnecessary gastrointestinal stress.