Altering the length-tension relationship with eccentric exercise : implications for performance and injury.

The effects of eccentric exercise on muscle injury prevention and athletic performance are emerging areas of interest to researchers. Of particular interest are the adaptations that occur after a single bout, or multiple bouts of eccentric exercise. It has been established that after certain types of eccentric exercise, the optimum length of tension development in muscle can be shifted to longer muscle lengths. Altering the length-tension relationship can have a profound influence on human movements. It is thought that the length-tension relationship is influenced by the structural makeup of muscle. However, the mechanism responsible for the shift in optimum length is not readily agreed upon. Despite the conflict, several studies have reported a shift in optimum length after eccentric exercise. Unfortunately, very few of these studies have been randomised, controlled training studies, and the duration of the shift has not yet been established. Nonetheless, this adaptation may result in greater structural stability at longer muscle lengths and consequently may have interesting implications for injury prevention and athletic performance. Both contentions remain relatively unexplored and provide the focus of this review.