Eight Seconds of Static Stretching Increases Flexibility and Maintains the Strength of the Rectus Femoris

Abstract

[Purpose] To clarify the effects of short-duration static stretching on the strength and flexibility of the rectus femoris muscle. [Subjects and Methods] Thirty healthy young individuals who exercised less than two days per week participated in this study. The right legs of all the subjects were examined. Heel-buttock distance in the prone position, strain ratio measured by ultrasound elastography of the rectus femoris, and knee extension isometric strength were measured before and after 2, 4, 6, 8, 10, and 30 sec of static stretching. [Results] Heel-buttock distance was reduced after all of the stretching times. The strain ratio improved after 8, 10, and 30 sec stretching, and isometric strength decreased after 10 and 30 sec stretching. [Conclusion] These results indicate that muscle strength was preserved after 8 sec of static stretching and flexibility was improved.