Author(s): AMPE, T., ARENALES ARAUZ, Y.L., DEMUYSER, T., ROELANDS, B., DE PAUW, K., Institution: VRIJE UNIVERSITEIT BRUSSEL, Country: BELGIUM, Abstract-ID: 1685

INTRODUCTION:
Both ultrarunning, an extreme sport pushing participants to their physiological limits, and the gut microbiota have gained enormous interest in recent years. Despite this growing interest, research on physiological responses during ultra-endurance events is limited, especially research on the relation with the gut microbiota1,2. Therefore, this study aims to fill this gap by exploring changes in the gut microbiota during a Backyard ultra-endurance running (BYR) event. Understanding these alterations is crucial for understanding their impact on energy metabolism, immune function and long-term health.
METHODS:
Eight male ultrarunners (41 ± 9 years old, BMI: 23.0 ± 1.1 kg/m²), with personal BYR records ranging from 100.5 km to 677 km, were monitored before, during and after a BYR event. Gut microbiome was examined before (pre), immediately after (post) and two weeks after the event (recovery). Athletes diets were tracked using Food Frequency Questionnaires (pre and recovery) and food diaries (during). Together with the diet, other gut related metadata (e.g. medicines, surgeries,…), as well as performance data during the event (e.g. heart rate, pace, lactate,…) were collected in order to correlate and/or correct for during the gut microbiome analysis.
RESULTS:
Preliminary results show differences in beta-diversity of the gut microbiome between pre, post and recovery samples. On phylum level, a shift in the Bacteroidetes/Firmicutes ratio was observed, with a decreased abundance of Bacteroidetes post event compared to pre event in 6 out of 8 athletes. Additionally, in 6 out of 8 recovery samples, an increased abundance of Bacteroidetes compared to post and pre event was shown. Consistently, on family level, Prevotellaceae exhibited lower abundance in the post and higher abundance in the recovery samples. For Bifidobacteriaceae a higher abundance was found post event for 5 athletes. Lastly, results indicate a high variance in Lachnospiraceae abundance across the different time points.
CONCLUSION:
Performing an ultra-endurance running event is associated with a temporary shift in bacterial composition in the gut and with the increased/decreased representation of some bacterial phyla and families immediately after the event and after recovery. Correcting for and/or correlating the gut microbiome data with the diet and metadata of the athletes, should confirm these results. Notwithstanding, the abundance of Prevotellaceae and Lachnospiraceae are typically associated with a higher fiber intake, which was lower during the event. Further analysis on species level, as well as metabolomic analysis should reveal further details on the effect of an ultra-endurance running event on the gut microbiome.

1. Grosicki, G. J. et al. (2019). Rapid gut microbiome changes in a world‐class ultramarathon runner. Phys. Rep., 7(24), e14313.
2. Sato, M. et al. (2022). Alterations in intestinal microbiota in ultramarathon runners. Sci. Rep., 12(1), 6984.