Background The formation of cardiac fibroid deposits due to intense exercise may be involved in cardiac arrhythmias. Galectin-3 (Gal-3) and suppression of tumorogenicity2 (ST2) are considered as markers for fibrosis development and cardiac remodeling.

Objective The aim of our study was to examine the evolution of both in trailers who ran the Tor des Géants (TdG).

Design Longitudinal, cohort study

Setting The TdG, a 330 km long ultra-distance trail running, with +24,000m elevation changes, is considered as one of the most difficult mountain marathon race in the world.

Patients (or Participants) 51 participants have been followed and the study was conducted on 33 subjects having reached at least half of the race.

Interventions (or Assessment of Risk Factors) Blood and urine samples collection were carried out at 4 key time points: before, during (mid-point) and after the race (less than 1h) and 3 days after the end of the race.

Main Outcome Measurements Levels of plasma Gal-3 and ST2 were determined at the 4 times. We calculated the difference between the different times in delta. Results were considered as significant with p<0.05.

Results We observed an increase for Gal-3 and ST2, above the reference values only for ST2. We noted for both a decrease up to the normal values 3 days after the trail. For the correlation between deltas, we observed that Gal-3 and ST2 are correlated for each delta.

Conclusions The results of this study demonstrate that this exercise was associated with biochemical abnormalities that may reflect adverse consequences on cardiac structure as fibrosis. ST2 values were higher, perhaps due to a mechanical stress more than a cardiac stress.