Rectus Femoris Stretching Effect on Antagonist Muscles Strength in High-Speed Runners

Abstract

Hamstring strain injury (HSI) is the most common injury in sports including high-speed running. Hamstring muscles main activation during sprinting is mainly in late swing phase in which they have to activate against hip flexors force. The purpose of this study was to analyse if rectus femoris (RF) muscle stretching produces immediate strength and activation increase in hamstrings muscles. An open-label, single-arm, control, pretest-posttest clinical trial was conducted. The study was carried out in the Aragonese centre of Sports and 16 (10 women and six men) high speed runners were recruited. Rectus femoris length and hamstrings isometric strength were registered as main outcomes and surface electromyography (sEMG), tensiomyography (TMG) variables and pelvic position were considered secondary outcomes: No differences were observed for any of the variables between baseline and control measurements. An increase in RF length (p<.002) and in hamstring isometric strength (p<.001) was registered between baseline and post-treatment measurements with a large effect size for both, 0.88 and 0.81 respectively measured by Cohen´s d.-test. It seems hamstring isometric strength improves immediately after performing RF static muscle stretching in young high-speed runners with RF shortening.