Fig. 1

Identification of discriminating biomarkers by metabolomics analysis. The PCA (a) and OPLS-DA (c) score plot are in negative ion mode. PCA (b) and OPLS-DA (d) score plot are in positive ion mode following marathon. Validation plot of 200 permutation tests for OPLS-DA model is built for negative (e) and positive ion mode (f) before and after marathon. The slope of R2 is greater than 0 and the intercept of Q2 on Y axis is less than 0.05, indicating a valid model