In recent years, there has been an increasing practical, clinical and scientific interest in the effects of free radicals and antioxidants related to sporting activities and exercise performance (Nikolaidis et al. 2012a,b; Peternelj and Coombes 2011; Powers et al. 2011; Reid 2008; Stear et al. 2009). Most of these reviews agree that oxidative stress represents a fundamental biological response to exercise stimuli. The generation of reactive oxygen species (ROS) increases with inclining oxygen utilisation during endurance exercises and is potentially associated with the risk of damage to muscles and other tissues. The key question is how effectively athletes can defend against the increased free radicals resulting from exercise. Do athletes need to take extra antioxidants? Studies provide arguments for and against the use of antioxidants but also emphasise that additional research will be required until a final judgement can be made (Peternelj and Coombes 2011; Powers et al. 2011; Stear et al. 2009). Obviously, large discrepancies exist between scientific evidence and the promotion by manufacturers and distributors of antioxidants. The promises of manufacturers and distributors are often based on anecdotal reports, not well-controlled observational studies or even on theoretical assumptions or speculations. It is readily understandable that the expectations of athletes encourage business interests. However, the main goal of scientific studies is to find the truth. To accomplish this goal, appropriate study design and sound statistical methods are of utmost importance.
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