The aim of this study was to examine the tendinous inscription (TI) of the human semitendinosus (ST) muscle using dissection (cadavers) and ultrasound (in vivo). Ultrasonography (US) scans were taken in 18 young males at rest and at maximum voluntary contraction (MVC). Further, the ST was dissected and removed from its origins in 10 cadaveric specimens (5 cadavers). The cadaveric long arm of the TI was 6.67 ± 0.64 cm (6.45 ± 1.21 in US) while the shorter arm was 2.39 ± 0.38 cm (1.99 ± 0.75 in US). The angle formed by the two TI arms ranged from 53.19 (US) to 56.05° (cadavers) while more superficial fascicles intersected the inscription at significantly higher angles (range 31.98 ± 6.15 to 34.69 ± 7.71°) compared with deeper fascicles (p < 0.05). Fascicle length did not differ between compartments, but it was significantly smaller in superficial compared with deeper layers (p < 0.05). With the exception of the angle between the TI arm and the deep aponeurosis, all measured angles as well as the length of the long arm of the TI increased significantly from rest to MVC (p < 0.05). The role of the TI probably lies in the local interconnections with the fascicles of either compartment, which upon contraction is such that the ST muscle contracts as one muscle. However, the TI arm morphology changes from rest to MVC, indicating a nonuniform displacement of the TI, mainly between the superficial and deeper layers of the muscle.
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