MyotonPRO-derived hamstring mechanical properties across testing positions and their associations with maximal strength

The MyotonPRO is increasingly used to quantify skeletal muscle mechanical properties; however, hamstring measurements may vary across testing positions, and the relationships between these measurements and maximal strength remain unclear. This study investigated differences in MyotonPRO-derived mechanical properties of the biceps femoris and semitendinosus across four testing positions and examined their exploratory associations with maximal isometric hamstring strength. Thirty healthy adults (18 males, 12 females; age 27.4 ± 4.9 years) underwent MyotonPRO assessment in the prone position, prone with the knee flexed to 90°, bilateral standing, and single-leg standing. Oscillation frequency, dynamic stiffness, logarithmic decrement, relaxation time, and creep were measured in both muscles. Maximal isometric hamstring strength was assessed using the End Range Hamstring Strength Test with handheld dynamometry. MyotonPRO-derived mechanical properties differed significantly across testing positions, with large position effects (partial η² = 0.355-0.822). Stiffness and oscillation frequency generally increased toward weight-bearing positions, whereas relaxation time and creep decreased; logarithmic decrement showed a less consistent pattern. Exploratory correlation analyses showed moderate-to-strong associations between maximal hamstring strength and stiffness, frequency, and relaxation time, as well as creep (|r| = 0.38-0.67), whereas logarithmic decrement showed weaker and more variable associations. In an exploratory hierarchical regression, adding logarithmic decrement to the selected stiffness measure increased R² from 0.440 to 0.500, but the incremental change was not statistically significant (ΔR² = 0.060, p = 0.082). These findings indicate that MyotonPRO-derived hamstring mechanical properties differ across testing positions and should therefore be interpreted within standardized testing conditions.