Eccentric Exercise, Muscle Damage and Oxidative Stress

Abstract

Participation in exercise has been linked with positive results on the cardiovascular system, metabolism, musculature etc. Some of these benefits are linked with reductions in blood pressure, increases in resting energy expenditure, changes in lipid profile, reductions in fat mass, increases in fat free mass etc. (Evans, 1999). There are different types of exercise that someone can participate in, i.e. walking, running, lifting weights, participating in organized sports which involve different muscular contractions. Isometric, concentric and eccentric muscle actions are the main muscular contractions involved in all exercise activities. Eccentric muscular contraction is this type of contraction where the length of the muscle is increased while tension is developed. Unaccustomed eccentric exercise has been linked with greater muscle damage compared to isometric or concentric muscular contractions. However this phenomenon is temporary and perturbations in functional and biochemical indices are back to normal within a week from the initiation of the trauma. Furthermore, the damage works as a protective mechanism since data indicates that the muscle damage is attenuated when a subsequent exercise bout of the same intensity is performed even a few months later. Eventhough eccentric exercise leads to greater muscle damage, recent data indicates that eccentrically induced muscle damage is related with positive changes in lipid profile that are evident for a few days following the initial event. Furthermore, the limited data from eccentric training studies indicate that this type of exercise is linked with positive changes in strength as well as in the metabolic profile of the exercise participant. Oxidative stress indicates a condition where the cellular production of pro-oxidant molecules exceeds the ability of the antioxidant system to reduce reactive oxygen or nitrogen species (RONS). There are several studies that indicate that oxidative stress is evident following muscle damaging exercise. Its role has been related to cleaning the debris from the damaged tissue and providing the means for biochemical adaptations that lead to a stronger and more resistant to muscle damage muscular tissue.