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  • Impact of hip flexion angle on unilateral and bilateral nordic hamstring exercise torque and high- density electromyography activity

    Author(s)
    Hegyi, A
    Lahti, J
    Giacomo, JP
    Gerus, P
    Cronin, NJ
    Morin, JB
    Griffith University Author(s)
    Cronin, Neil
    Year published
    2019
    Metadata
    Show full item record
    Abstract
    Background: In the bilateral Nordic hamstring exercise (NHE), hamstrings operate at relatively short lengths, which may limit the efficacy of the NHE in hamstring injury prevention. Objectives: To examine knee flexion torque and biceps femoris long head (BFLH) and semitendinosus (ST) high-density electromyography (EMG) activity during the unilateral and bilateral NHE, performed with either neutral (NHE0) or 90°-flexed (NHE90) hips. Methods: In this laboratory study, exercises were performed on a novel device at the eccentric 1-repetition maximum load defined for 90° to 15° of knee range of motion. Torque and EMG signals ...
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    Background: In the bilateral Nordic hamstring exercise (NHE), hamstrings operate at relatively short lengths, which may limit the efficacy of the NHE in hamstring injury prevention. Objectives: To examine knee flexion torque and biceps femoris long head (BFLH) and semitendinosus (ST) high-density electromyography (EMG) activity during the unilateral and bilateral NHE, performed with either neutral (NHE0) or 90°-flexed (NHE90) hips. Methods: In this laboratory study, exercises were performed on a novel device at the eccentric 1-repetition maximum load defined for 90° to 15° of knee range of motion. Torque and EMG signals normalized to maximal voluntary isometric activity were compared in different phases of the exercises with statistical parametric mapping. Results: The EMG levels were lower in NHE90 than in NHE0, mainly in the second half of the movement. Knee flexor eccentric torque was higher in NHE90 than in NHE0 from the beginning to 87% of the bilateral movement, and over the entire unilateral movement. In NHE0, ST activity compared to BFLH activity was higher during the initial movement phase and lower when the movement was close to knee extension. Torque and EMG activity were generally similar in the bilateral and unilateral modes. Conclusion: If performed with neutral hips, the NHE selectively activates the BFLH near full knee extension. Performing the NHE with hips flexed to 90° is preferable when higher passive torque and ST selectivity are targeted at a longer muscle length. Performing these exercises unilaterally could help train each limb separately, with similar torque and EMG output to those of the bilateral conditions.
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    Journal Title
    Journal of Orthopaedic and Sports Physical Therapy
    Volume
    49
    Issue
    8
    DOI
    https://doi.org/10.2519/jospt.2019.8801
    Copyright Statement
    Self-archiving of the author-manuscript version is not yet supported by this journal. Please refer to the journal link for access to the definitive, published version or contact the author[s] for more information.
    Subject
    Clinical sciences
    Sports science and exercise
    biceps femoris
    rehabilitation
    semitendinosus
    strain injury
    Publication URI
    http://hdl.handle.net/10072/396390
    Collection
    • Journal articles

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