Hamstring stiffness pattern during contraction in healthy individuals: analysis by ultrasound-based shear wave...

Area of Science:

• Biomechanics
• Musculoskeletal Ultrasound
• Rehabilitation Science

Background:

• Assessing hamstring muscle stiffness is crucial for understanding muscle function and injury.
• Ultrasound-based shear wave elastography (SWE) offers a non-invasive method to evaluate tissue mechanical properties.

Purpose of the Study:

• To evaluate the repeatability of SWE for hamstring stiffness assessment.
• To characterize hamstring muscle (semitendinosus and biceps femoris long head) stiffness during isometric contractions.
• To examine stiffness distribution and inter-limb symmetry in healthy individuals.

Main Methods:

• Two experiments were conducted on healthy participants assessing intra- and inter-day repeatability.
• Hamstring stiffness was measured using SWE at varying maximal voluntary isometric contraction (MVIC) intensities (10-60%).
• Measurements were taken with the knee flexed at 30° and hip neutral.

Main Results:

• High intra- and inter-day repeatability (ICC = 0.69-0.93) was observed for hamstring stiffness assessment.
• The biceps femoris long head (BFlh) to semitendinosus (ST) stiffness ratio increased with contraction intensity.
• The ST was stiffer than other hamstring muscles at 20% MVIC, with symmetric stiffness between limbs.

Conclusions:

• Shear wave elastography demonstrates high reliability for assessing hamstring muscle stiffness during isometric contractions.
• Hamstring muscle stiffness distribution is heterogeneous but symmetric between limbs.
• Muscle stiffness varies significantly with contraction intensity.