Abstract

Skeletal muscle contraction as a consequence of physical activity is characterized by a significant rise in the formation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) known as the oxidants. In accordance with the intensity, duration, type of exercise, and fitness level of the athlete, the exercise-associated oxidative stress might result in negative or positive effects on muscle integrity and performance. At high and uncontrolled levels, ROS/RNS cause lipid peroxidation, oxidation of proteins and DNA molecules, dysfunction of excitation-contraction coupling, and muscle damage. In contrast, at lower physiological levels of ROS, these molecules are responsible for important signaling functions involved in promoting mitochondrial biogenesis, stimulating antioxidant defenses, and triggering adaptive responses to physical training in accordance with the concept of hormesis. The present review covers information about cellular sources of exercise-induced ROS/RNS, mechanisms of oxidative damage to contractile and metabolic components of muscle cells, a double-faced effect of oxidants in muscle fatigue and adaptation, effect of the athlete's training status and exercise type, and debates regarding the antioxidant supplementation among athletes. Keywords: oxidative stress; reactive oxygen species; skeletal muscle; exercise; antioxidants; muscle fatigue; redox signalling.