**5. Conclusions**

Interestingly, the study yielded new results regarding the age of the runners. Senior runners (45–53) showed significant higher levels of lipid peroxidation (MDA concentration) than medium (38–44) and young runners (31–37) throughout the study. A plausible explanation would be the higher body fat percentage observed in senior runners, together with the loss of muscular mass compared to younger runners (Table 1). These results are in agreement with Hattori and cols. who reported that ultramarathon runners aging less than 45 years old had lower ROS levels at all race points [51]. Again, larger series would be necessary to study the predictive value of this assay to consider if a personalized antioxidant supplementation might promote the physiological recovery after great physical efforts.

**Supplementary Materials:** The following are available online at https://www.mdpi.com/2076-392 1/10/3/355/s1, Supplementary Table S1. Evolution of muscle strength (SJ and HG), muscle damage (LDH and CK) and acute inflammation (CRP) biomarkers.

**Author Contributions:** Conceptualization, C.G., C.H., E.C.-B. and M.M.; methodology, P.B., B.H. and C.H.; formal analysis, C.G., M.M. and C.H.; investigation, Barbara Hernando, I.M.-N. and C.H.; writing—original draft preparation, E.C.-B., C.G., C.H.; writing—M.M., P.B., C.H.; funding acquisition, C.H. and I.M.-N. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by Vithas Hospitals group (https://vithas.es), Penyagolosa Trails organization (http://penyagolosatrails.com), catedra Endavant Villarreal CF de l'Esport (https://endavant.villarrealcf.es/) and the following grant code: UJI-B2019-38. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

**Institutional Review Board Statement:** The investigation was conducted in accordance with the Declaration of Helsinki and approval for the project was obtained from the research Ethics Committee of the University Jaume I of Castellon (Expedient Number CD/007/2019). This study is enrolled in the ClinicalTrails.gov database, with the code number NCT03990259 (www.clinicaltrials.gov).

**Informed Consent Statement:** Informed consent was obtained from all volunteers involved in the study.

**Data Availability Statement:** Data is contained within the article or supplementary material.

**Conflicts of Interest:** The authors declare no conflict of interest.
