Skeletal muscle consumes significant amounts of oxygen, and its oxygen flux increases significantly under conditions of exercise and muscle contraction. This makes the muscle vulnerable to oxidative stress since concomitantly with the increase of oxygen flow there is an increase of free oxygen radicals which are a byproduct of muscle respiration. A number of studies in the last decade have documented the involvement of free oxygen radicals in exercising muscles. The consequences of muscle oxidative stress have resulted mainly in increased muscle protein oxidation, elevation of lipid peroxidation, and depletion of muscle antioxidants. The mechanisms of this oxidative stress are under extensive investigation in laboratories around the world and are topics of the chapters in this volume. This book is intended for professionals who are interested in muscle function, physiology, pathophysiology and well-being, such as therapists, trainers and medical professionals as well as for researchers in the field of muscle physiology.