Hamstring Muscle Use in Females During Hip-Extension and the Nordic Hamstring Exercise: An fMRI Study.

J Orthop Sports Phys Ther. 2018 Apr 23;:1-23

Authors: Messer DJ, Bourne MN, Williams MD, Al Najjar A, Shield AJ

Abstract
Study Design Cross-sectional study. Background Understanding hamstring muscle activation patterns in resistance training exercises may have implications for the design of strength training and injury prevention programs. Unfortunately, surface electromyography studies have reported conflicting results with regard to hamstring muscle activation patterns in women. Objectives To determine the spatial patterns of hamstring muscle activity during the 45º hip-extension and Nordic hamstring exercises, in females using functional magnetic resonance imaging. Methods Six recreationally active females with no history of lower limb injury underwent functional magnetic resonance imaging (fMRI) on both thighs before and immediately after 5 sets of 6 bilateral eccentric contractions of the 45º hip-extension or Nordic exercises. Using fMRI, the transverse (T2) relaxation times were measured from pre- and post- exercise scans and the percentage increase in T2 was used as an index of muscle activation. Results fMRI revealed a significantly higher biceps femoris long head (BFLongHead) to semitendinosus ratio during the 45° hip-extension than the Nordic exercise (P = .028). The T2 increase after 45° hip-extension was greater for BFLongHead (P < .001), semitendinosus and semimembranosus (P = .001) than that of biceps femoris short head (BFShortHead). During the Nordic exercise, the T2 increase for semitendinosus was greater than that of BFShortHead (P < .001) and BFLongHead (P = .001). Conclusion While both exercises involve high levels of semitendinosus activation in women, the Nordic exercise preferentially recruits that muscle while the hip extension more evenly activates all of the biarticular hamstrings. J Orthop Sports Phys Ther, Epub 23 Apr 2018. doi:10.2519/jospt.2018.7748.

PMID: 29685059 [PubMed - as supplied by publisher]