Research Article Oxidative Stress Assessment in Response to Ultraendurance Exercise: Thiols Redox Status and ROS Production according to Duration of a Competitive Race Alessandra Vezzoli, 1 Cinzia Dellanoce, 2 Simona Mrakic-Sposta, 1 Michela Montorsi, 1,3 Sarah Moretti, 1 Annamaria Tonini, 2 Lorenza Pratali, 2 and Roberto Accinni 2 1 Institute of Bioimaging and Molecular Physiology, National Research Council (CNR), Via Fratelli Cervi 93, 20090 Segrate, Italy 2 Institute of Clinical Physiology, National Research Council (CNR), Niguarda Ca’ Granda Hospital, Via G. Moruzzi 1, 56124 Pisa, Italy 3 Telematic University San Rafaele, Via F. Daverio 7, 20122 Milan, Italy Correspondence should be addressed to Simona Mrakic-Sposta; simona.mrakic@ibfm.cnr.it Received 21 April 2016; Revised 23 May 2016; Accepted 24 May 2016 Academic Editor: Steven McAnulty Copyright © 2016 Alessandra Vezzoli et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Purpose. Response to an ultraendurance competitive race on thiols redox status, reactive oxygen species (ROS) production, and oxidative stress (OxS) was investigated according to duration. Methods. Twenty-four elite runners were examined: six completed 50 km and eighteen 100 km. Blood and urine samples were collected before and immediately afer the race. Erythrocytes and plasma aminothiols by high-performance liquid chromatography, total antioxidant capacity (TAC), and OxS biomarkers (protein carbonyl (PC), thiobarbituric acid-reactive substances (TBARS), 8-isoprostane (8-iso-PGF2), and 8-OH-2-deoxyguanosine (8-OH-dG)) by immunoenzymatic assays and ROS production by Electron Paramagnetic Resonance were assessed. Results. Signifcant increases ( between <0.05 and <0.0001) were recorded in plasma total and oxidized aminothiols concentration and TAC ( < 0.0001) only afer 100 km: plasmatic (ROS production (+12 versus +29%), PC (+54 versus +115%), and TBARS (+28 versus +55%)) and urinary (8-OH-dG.creatinine −1 (+71 versus +158%) and 8-iso-PGF2.creatinine −1 (+43 versus +135%)) concentrations for 50 and 100 km (duration 4 h 3  versus 8 h 42  ), respectively. Conclusion. Very prolonged ultraendurance exercise causes an increase in ROS production and OxS depending on specifc biomarker examined but always linearly and directly related to exercise duration. Redox status of erythrocytes was preserved. A relationship between running performance and both prerace ROS production and antioxidant-redox status was found in 100 km race. 1. Introduction Despite the many known health benefts of exercise, there is a body of evidence suggesting that moderate/vigorous physical activity results in enhanced formation of reactive oxygen species (ROS). Over the past 20 years, perceptions on the roles of ROS have changed and are now considered physiologically vital in the process of signal transduction. Despite this, if they are not balanced or cleared, then they may cause structural damage to various macromolecules [1]. Electron Paramag- netic Resonance (EPR) is the only technique that provides direct evidence of the “instantaneous” presence of ROS leading to absolute concentrations. However, most adopted methods for assessing oxidative stress (OxS) utilize the mea- surement of ROS-induced modifcations to proteins, DNA, and lipids. Adducts on these molecules, referred to as biomarkers, determined in blood correlate with similar mea- surements in tissues and therefore their assessment provides an indication of whole-body OxS [2]. Te vast majority of the human studies have measured the redox status of plasma. Tis is probably done due to the easiness of plasma collection and because it is assumed Hindawi Publishing Corporation Oxidative Medicine and Cellular Longevity Volume 2016, Article ID 6439037, 13 pages http://dx.doi.org/10.1155/2016/6439037