![]() Alfredson ( 1), and Alfredson and Lorentzon ( 2), a leading researcher in the area of achilles tendinosis, stated that the effects of loading induced hypertrophy, increased tensile strength, and the effect of stretching the muscle tendon unit were all positive adaptations from eccentric training. The most obvious is the increased eccentric strength of the calf muscles ( 2,6,52). There are many proposed reasons why eccentric strength training is an effective means of rehabilitation of achilles tendinosis. Currently, rehabilitation programs involving eccentric training using loads greater than body weight have provided positive results in the treatment of achilles tendinosis, with a decrease in pain and a higher percentage of patients returning to preinjury levels of physical activity ( 8,12,14,15,21,23,37,51,59). Therefore, many earlier researchers recommended eccentric training programs to increase eccentric strength in the tendons during running and jumping ( 32). ![]() Early researchers believed that because most tendon injuries occurred during the eccentric phase of muscle work, eccentric exercise would be a viable treatment modality ( 75). The eccentric training theory promoted the importance of structural adaptation of the symptomatic tendon, so it could cope with the increased repetitive loads and prevent injury ( 24). If these loads were repeated, as in many activities and sports, then a symptomatic tendon condition could result. Eccentric training models were based on the belief that tendon injuries could result from tensile loads exceeding the tendon's mechanical strength ( 24). One form of treatment that has gained popularity in the rehabilitation of achilles tendinosis is eccentric strength training. Other suggested etiologic factors include aging, decreased blood supply, decreased flexibility, muscle imbalance, decreased concentric and eccentric calf strength, faulty musculoskeletal alignment, and training errors ( 2). Depending on an individual's activity level, even short walks could be enough loading to cause overuse symptoms. Many authors have considered achilles tendinosis as an overuse injury from repetitive loading, but others have observed the condition in sedentary populations ( 11,52). Furthermore, as tendons are collagenous structures with limited blood supplies, their slow metabolic rate leads to an impaired healing response ( 5). In addition to a loss of collagen fibers, there is also a loss of fiber cross-links, which results in a reduction in tendon strength ( 2). ECCENTRIC LOADING FOR REHABILITATION OF ACHILLES TENDINOSISĪchilles tendinosis etiology is a degenerative process because of overuse where there are no inflammatory cells, but changes of the collagen fiber structure result in the tendon's inability to adapt to changes in loading patterns ( 15,17,23). This is by no means an exhaustive review of each of these areas but rather a brief introduction to the many faces of eccentric training. The physiologic rationale for each form of eccentric training and simple loading parameters are briefly described. Specifically, we will address the use of eccentric resistance training for (a) tendon injury rehabilitation via tendinous remodeling (b) muscle injury prevention via shift in the optimum length of muscle (c) supramaximal and/or accentuated eccentric loading (i.e., loads exceeding the 1 repetition maximum (1RM) and/or greater than the concentric load) for strength, performance, and hypertrophy and (d) improved sports performance via SSC optimization. This article discusses how we can modify the stress (load), strain (length or amplitude of movement), and velocity during the eccentric phase, to impose a variety of mechanical stimuli that have different adaptational and functional effects. It is the eccentric phase of this coupling that provides the focus of this article. Most human motion involves this eccentric–concentric coupling or SSC muscle action. Understanding these muscle actions and how to program them into a resistance training protocol is an essential component of successful strength and conditioning practice. For these requirements, the situational needs usually involve a blending of certain muscle actions-isometric, concentric, eccentric, or a coupling of an eccentric–concentric muscle action termed a stretch-shortening cycle (SSC). The job description of a strength and condidioning specialist will change with degrees of athlete preparation, injury prevention, and injury rehabilitation.
0 Comments
Leave a Reply. |