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Region-specific assessment of the mechanical properties of each hamstring muscle in human cadavers using shear wave
Gakuto Nakao1, Taiki Kodesho2, Kazuma Yamagata3
1Graduate School of Health Sciences, Sapporo Medical University, Sapporo, Japan; Professional Post-secondary Course (Physical Therapist), Sapporo Medical Technology, Welfare and Dentistry Professional Training College of Nishino Gakuen School Foundation, Sapporo, Japan.
Background:
Understanding regional mechanical properties of individual hamstring muscles is essential for accurately interpreting their functional behavior during elongation. However, how mechanical stress varies within muscles during elongation remains unclear. This study aimed to examine whether mechanical stresses differ among the hamstring muscles and at various regions within each muscle.
Methods:
Fifteen cadavers were dissected to study the biceps femoris long head, semitendinosus, and semimembranosus muscles. Proximal and distal tendons were attached to a mechanical testing machine, and muscles were stretched from slack length to 8 % strain. Muscle length was measured with a tape measure, and anatomical cross-sectional areas at proximal (33 %) and distal (67 %) regions were determined using B-mode ultrasonography. Strain and stress were calculated to assess mechanical properties, and shear modulus was measured using shear wave elastography at the same regions.
Findings:
A linear correlation between shear modulus and stress was found for all hamstring muscles (P < 0.01). Significant interactions among muscle, region, and strain were observed, with post-hoc tests revealing that the biceps femoris long head and semimembranosus had higher shear modulus than the semitendinosus after 0.5 % strain. The proximal biceps femoris long head showed increased shear modulus after 5 % strain, and proximal semimembranosus showed higher values after 0.5 % strain compared with the distal region.
Interpretation:
The study findings reveal region-specific variations in the mechanical properties both among and within the hamstring muscles. Combining shear wave elastography with mechanical testing offers a non-destructive approach for characterizing these variations in passive muscle behavior.
