Common Questions and Tentative Answers on How to Assess Oxidative Stress after Antioxidant Supplementation and Exercise

Redox biology has been one of the most rapidly developed fields of biology and one of the most popular in the mass media. Free radicals (reactive species in the present review) have been linked to many different biological processes, such as cell signalling (Forman et al. 2010), enzyme activity (Stubbe and Van Der Donk 1998), synthesis of antibiotic substances (Lesniak et al. 2005) and pathophysiology of diseases (Valko et al. 2007). From the results of thorough investigations conducted in the past three decades, it is now clear that acute exercise induces oxidative stress, whereas chronic exercise enhances the endogenous antioxidant mechanisms (Camiletti-Moirón et al. 2013; Theodorou et al. 2011). Along with the progress of the exercise redox biology, the molecular and biochemical properties of many nutrient compounds possessing redox properties (i.e. pro-oxidants and mostly antioxidants) have also been revealed. However, despite the long-standing research efforts, it is still uncertain whether and how the exogenous administered antioxidants affect redox homeostasis and physical performance (Bell et al. 2013; Braakhuis 2012; Nikolaidis 2012c; Peternelj and Coombes 2011; Powers et al. 2010). Why did it prove to be difficult to reveal the effects of antioxidant supplementation on oxidative stress and human physiology? We believe that the main reason is the methodological uniqueness of each study, particularly regarding the research strategy that investigators adopt on issues relevant to redox biology. Taking into account that redox biology of exercise is a relatively new field, research is driven more on intuition and less on sound methodological evidence. Thus, it is desirable to develop and achieve some agreement on key influencing factors, which investigators should take into account when designing studies in the area of redox biology. Therefore, the aim of this chapter is to provide a methodological framework and broad directions on setting up appropriate experimental set-ups. In particular, we have introduced and tentatively answered eight questions, which a researcher may come across when designing experiments in the redox biology of exercise. It is emphasised, particularly considering the inherent complexity of redox biochemistry, that the following answers are based on the current knowledge; therefore, they can always be amended or disproved by new evidence and should not be accepted as the final answers.