Author(s): Michael LaForce
Mentor(s): Brent Feland, Camille L. Nguyen
Institution BYU
Introduction: Various techniques have been employed to assess hamstring stiffness; however, ultrasound sheer wave elastography (SWE) remains a relatively novel approach in this area. Ultrasound SWE allows for a quantitative rather than qualitative approach by calculating the stiffness of a muscle in kilopascals (kPa); muscles in their most relaxed state exhibit lower kPa numbers while contracted, tense, or injured muscles exhibit higher numbers. By obtaining quantitative measurements of hamstring stiffness, future research can investigate how different therapeutic modalities affect the stiffness of a muscle, providing precise numerical data for analysis. Purpose: The aim of our study was to obtain average stiffness measurements (kPa) of the semitendinosus (ST) and semimembranosus (SM) hamstring muscles using ultrasound SWE and assess the differences in stiffness values in two different positions. Methods: Seven healthy volunteers (height: 180±6.83 cm, weight: 73±8.668 kg, age: 21±1.80 years) with no history of hamstring injury were assessed once in our lab, measuring each muscle at 50% of the length between the greater trochanter and lateral epicondyle. Each measurement was acquired by identifying the target muscle in a short-axis view superior to the anterior knee and subsequently tracking the muscle fascicle to 50% of its length, at which point a measurement was obtained in a long-axis view. We acquired three cine loops per muscle for both the elevated (bolster) and normal positions, resulting in a total of 30 repeated measurements for each muscle in both positions. Results: Data were analyzed using SPSS ver. 29 and checked for normality. There was a significant difference in stiffness values between the bolster and normal position (p=0.002), while ST demonstrated stiffer values (p=0.012) regardless of position (p=0.004). Thus, there was a significant interaction for position and muscle. Variance of kPa measurements were higher for ST than SM for both bolster and normal positions. Conclusion/Clinical significance: Hamstring stiffness values are significantly reduced when subjects’ ankles are elevated in the bolster position. The SM muscle had relatively stable kPa values regardless of measurement position with ST showing greater variance, particularly in the normal position. Stiffness values were higher for both muscles in the normal vs the bolster position. Ultrasound SWE effectively discerns between muscle length stiffness differences and the SM muscle may be more reliable for repeated measures when considering future studies involving muscle interventions.