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A study was conducted using two muscles of different connective tissue content [13.13 ± 3.11 and 2.47 ± 0.95 mg collagen/g of muscle for sternomandibularis (S) and psoas major (PM) muscles, respectively], which had shortened to various sarcomere lengths (1.35-2.6 μm and 1.7-3.25 μm for the S and PM muscles, respectively). Differences in structural preservation of the mitochondria, triads and Z-lines were noted for the stretched and contracted samples of both muscles. The difference in connective tissue of the two muscles was related to the differences in tenderness of these muscles at all sarcomere lengths. However, the difference in tenderness of these muscles was not constant at all sarcomere lengths, with the S muscle decreasing in shear force at a faster rate due to increasing sarcomere length. This phenomena is probably due to a toughening of both connective tissue and muscle fibers as the S muscle shortens, whereas, in the PM muscle, only the muscle fibers cause a toughening due to shortening. This study also indicates the effectiveness of using a trained sensory panel to detect connective tissue and muscle fiber tenderness separately. |
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