Acute Effect of Active and Passive Static Stretching on Elastic Modulus of the Hamstrings.

The purpose of this study was to investigate differences in the acute effects of passive knee extension (PKE) and active knee extension (AKE) stretching on the shear elastic modulus of the hamstrings. In 20 healthy men, maximum knee extension (maximum range of motion [ROM]) and shear elastic modulus of the hamstrings (biceps femoris long head, semitendinosus, semimembranosus) were measured before (Pre) and after (Post) AKE and PKE stretching. The maximum ROM during stretching was measured. In both stretching methods, maximum ROM increased and the shear elastic modulus decreased (p<0.01), but no difference was found between the procedures. No significant difference was observed in the maximum ROM during stretching between the procedures (p=0.06). The shear elastic modulus was significantly lower in the biceps femoris long head and semimembranosus than in the semitendinosus muscle (p<0.05). Static stretching with PKE and AKE stretching showed an increase in maximum ROM and a decrease in hamstring elasticity, but no difference was found between the methods. Both stretching protocols were effective for reducing elasticity of the biceps femoris long head and semimembranosus.