Supplemental Antioxidants and Adaptation to Physical Training

Excerpt

Free radicals are commonly thought of as perpetrators of cell damage, ageing and even cancer, while antioxidants are seen as the defence against these threats. As awareness about the harmful effects of free radicals has increased, so has consciousness regarding the importance of dietary antioxidants. As a result, many health-conscious people turn to nutritional supplements containing vitamins and other antioxidants. Particular interest in antioxidant supplements has arisen among athletes and people who train regularly. Indeed, antioxidants are among the most common sport supplements used by amateur and professional athletes (Krumbach et al. 1999; Margaritis and Rousseau 2008; Sobal and Marquart 1994). A quick survey of the labels on most energy bars and recovery drinks would seem to erase any doubt that athletes have an extraordinary need for antioxidants. However, it has not been conclusively shown that this is the case, and it remains debatable whether large amounts of supplementary antioxidants are sensible at all for athletes in training (Padilla and Mickleborough 2007).

Indeed, there is a growing body of evidence that the appearance of free radicals in skeletal muscle, besides having certain negative effects, also fulfils important physiological functions in cells, and that the right balance between antioxidants and free radicals is necessary for the desired physiological adaptations (Gomez-Cabrera et al. 2008; Ji 2008). Thus, it becomes necessary to assess the prudence of antioxidant supplementation, particularly among athletes in training (Gross et al. 2011).

In this chapter, we briefly address the production of free radicals at rest as well as during and in response to exercise or training. Then we reflect upon the negative and positive effects free radicals can have on skeletal muscles, highlighting the signalling functions of free radicals in the process of physiological adaptation to training. Finally, the influence of supplemental antioxidants on free radical biology and training adaptations is discussed. An overview of the situation discussed in this chapter is presented in Figure 7.1.