Hamstring stiffness pattern during contraction in healthy individuals: analysis by ultrasound-based shear wave elastography
To assess the stiffness of hamstring muscles during isometric contractions in healthy individuals, using ultrasound-based shear wave elastography to (1) determine the intra- and inter-day assessment repeatability, (2) characterize the stiffness of semitendinosus (ST) and biceps femoris long head (BFlh) along the contraction intensity, and (3) characterize stiffness distribution among the hamstring muscles and inter-limb symmetry.
Two experiments were conducted. In experiment I (n = 12), the intra-day repeatability in assessing the BFlh and ST stiffness were determined at intensities between 10–60% of maximal voluntary isometric contraction (MVIC) in a single session. In experiment II (n = 11), the stiffness of the hamstring muscles of both thighs was assessed at 20% of MVIC in the first session; and retested (for one randomly chosen thigh) in a second session. Isometric contraction of knee flexors was performed with the knee flexed at 30° and with the hip in a neutral position.
Moderate-to-very-high intra- and inter-day repeatability was found (ICC = 0.69–0.93). The BFlh/ST stiffness ratio increased with contraction intensity. At 20% of MVIC, the ST showed the highest stiffness among the hamstring muscles (p < 0.02), with no differences between the remaining hamstring muscles (p > 0.474). No differences were found between limbs (p = 0.12).
The stiffness distribution among the hamstring muscles during submaximal isometric contractions is heterogeneous, but symmetric between limbs, and changes depending on the contraction intensity. Shear wave elastography is a reliable tool to assess the stiffness of hamstring muscles during contraction.
KeywordsSurface EMG Shear modulus Skeletal muscle Biceps femoris short head Semitendinosus
Biceps femoris long head
Biceps femoris long head to semitendinosus ratio
Biceps femoris short head
Cohen effect size
Intraclass correlation coefficient
Maximum voluntary isometric contractions
Pearson correlation coefficient
Standard error of measurement
Ultrasound-based shear wave elastography
The authors confirm that they have read the Journal’s position on issues involved in ethical publication and affirm that this report is consistent with those guidelines.
All authors conceived and designed the research. TF and BM conducted experiments. TN processed the data. TF and BM analyzed data. TF and BM wrote the manuscript. All authors read and approved the manuscript.
Compliance with ethical standards
Conflict of interest
None of the authors has any conflict of interest to disclose. JV is funded by P20GM109090.
Informed consent was obtained from all individual participants included in the study. We are thankful to Mr. Vitor Meha for his great contribution in the experimental setup.