ABSTRACT
Owing to the potential for cellular damage, much controversy was created by initial reports that indicated that physical exercise increased the production of reactive oxygen species (ROS). The nicotinamide adenine dinucleotide phosphate oxidases are a family of enzymes first identified in phagocytes with a primary function of generating ROS as part of the innate immune response to pathogens. In summary, the electron transport chain is the site for mitochondrial respiration resulting in oxygen consumption leading to adenosine triphosphate synthesis. The chapter aims to briefly explain the main pathways in the human body, which lead to free radical production, and then to highlight the impact of free radical regulation in both cardiac and skeletal muscle tissues. Superoxide production from the xanthine oxidase pathway, however, might be species dependent and the overall impact of this pathway in human muscle remains to be fully appreciated.
