Eccentric Muscle Contraction

These are common in the adolescent age group, particularly those involved in physical activity. In acute injuries, they are the result of extreme, unbalanced and often eccentric muscle contraction. In more chronic cases, they are the result of repetitive microtrauma and overuse (Tehranzadeh 1987 El-Khoury et al. 1997 Stevens et al. 1999). The fracture occurs at the muscle attachment or tendon insertion on the bone. In adolescents, these attachments and insertions are often onto an apophysis, where the growth cartilage is an area of relative weakness. In addition, the bone in young people is relatively weaker and more elastic, so consequently it is this bone attachment that is more prone to injury than the musculo-ten-dinous junction. Not until early adulthood does the musculo-tendinous junction become the point of relative weakness and muscle and tendon tears the commoner injury. 

During muscle contraction, the force is transmitted to the skeleton by the tendon or aponeurosis and may or may not result in joint motion. There are three different types of muscle contraction isometric, when the muscle contracts but there is no change in its length (Fig. 3.3a,d) isotonic, when the muscle contracts and simultaneously shortens (Fig. 3.3b,e) and eccentric, when the muscle contracts and, at the same time, lengthens (Fig. 3.3c,0. 

Several muscles attached onto the pelvic bones are subjected to considerable tensile forces, often related to eccentric muscle contractions. Injury... 

Eccentric— a contraction in which a muscle lengthens while continuing to maintain tension [Gowitzke etal, 1980]. 

Komi P.V. 1973. Measurement of the force-velocity relationship in human muscle under concentric and eccentric contractions. In S. Cerquighni, A. Venerando, and J. Wartenweiler (Eds.), Biomechanics III, pp. 224-229. Baltimore, University Park Press. 

Eccentric contraction. The muscle lengthens, using extensibility to perform the task. 

In the upright position, the eccentric contraction (lengthening) of the extensor muscles controls the speed of forward bending. These muscles are exercised. 

Sugita M, Ohtani M, Ishii N, Maruyama K, Kobayashi K. Effect of a selected amino acid mixture on the recovery from muscle fatigue during and after eccentric contraction exercise training. Biosci Biotechnol Biochem 2003 67 372-375. 

Muscle strains most often occur as a result of powerful stretching when the muscle is contracted. This typically occurs during an eccentric contraction, when the muscle is being lengthened as it activates (Zarins and Ciullo 1983). In these cases, there is... 

Yeung, E. W. Ballard, H. J. Bourreau, J. P. Allen, D. G. Intracellular sodium in mammalian muscle fibers after eccentric contractions. J. Appl. Physiol. 2003, 94, 2475-2482. 

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