Dominant and Nondominant Side Patterns in Hamstring Stiffness and Clinical Flexibility in Amateur Football Players...

Football-specific loading may be associated with different dominant and nondominant (D and ND) side patterns in hamstring stiffness and clinical flexibility. This study compared D and ND side patterns in semitendinosus (ST), semimembranosus (SM), and biceps femoris (BF) stiffness and in active knee extension (AKE) and straight leg raise (SLR) measurements between amateur football players and healthy controls.

This cross-sectional study included 50 amateur football players and 50 healthy controls without organized athletic participation. Bilateral ST, SM, and BF stiffness values were measured using shear wave elastography (SWE). Clinical hamstring flexibility was assessed with AKE and SLR tests. D and ND side differences were examined within each group, and side difference patterns were compared between groups.

In football players, SM stiffness was higher on the dominant side (D-ND estimate, 1.25 kPa, p = 0.012). In controls, BF stiffness was higher on the nondominant side (D-ND estimate, - 0.90 kPa, p = 0.044). In the primary between group comparison, only the BF D-ND difference differed significantly, with opposite directions of side difference between groups (between group estimate, 1.74 kPa, p = 0.013). Controls also showed dominant side AKE and SLR differences of 1.00° and 1.50°, both below reported measurement error thresholds.

D and ND side patterns in hamstring stiffness and clinical flexibility varied according to the muscle, test, and group studied. The main between group difference emerged through BF stiffness, whereas the AKE and SLR differences observed in controls were limited in magnitude.