Keerasomboon Taspol, Soga Toshiaki, Hirose Norikazu
College of Sports Science and Technology, Mahidol University.
Graduate School of Sport Sciences, Waseda University.
Int J Sports Phys Ther. 2022 Aug 1;17(5):832-840. doi: 10.26603/001c.36627. eCollection 2022.
Previous studies have shown that performing the Nordic hamstring exercise (NHE) with different board slope angles can affect hamstring activation. However, changes in muscle length with different board slopes can alter joint angles leading to the moment arm (MA) at the knee changing during the NHE.
This study aimed to investigate the influence of changing muscle length on hamstring electromyographic activity during an isometric NHE, while maintaining an equal moment arm.
A crossover study design.
Sixteen male volunteers performed two types of conventional NHE, one with knees on the floor (NHE) and one with the legs placed upon an incline slope of a lower leg board (NHEB). To compare between the conventional and inclined NHE, the moment arm at the knee was calculated to be equal by an examiner holding the lower legs at points marked at 77% and 94% of the length of the lower leg. The four sub-groups comprised of: 1) NHE-77%, 2) NHE-94%, 3) NHEB-77%, and 4) NHEB-94%. The hamstring EMG activity was measured at the biceps femoris long head (BFlh) and at the semitendinosus (ST) and related compensatory muscles. The RMS data were normalized as a percentage of the maximum isometric values (normalized EMG [nEMG]). Significant main effects findings were followed up with Tukey's post-hoc test using SPSS software and statistical significance was set at the p < 0.05 level.
The BFlh EMG activity values for NHE-77% were significantly higher than those for NHE-94% (p= 0.036) and NHEB-77% (p < 0.001), respectively, while ST during NHE-77% was significantly higher only in NHEB-77% (p < 0.001). In addition, NHEB-94% was significantly greater than NHEB-77% for both BFlh (p < 0.001) and ST (p < 0.001).
These results indicate that hamstring electromyographic activity is decreased when the hamstring muscle is lengthened during the Nordic hamstring exercise.
先前的研究表明，以不同的木板倾斜角度进行北欧式腿弯举运动（NHE）会影响腘绳肌的激活。然而，不同木板倾斜度下肌肉长度的变化会改变关节角度，导致在NHE过程中膝关节处的力臂（MA）发生变化。
本研究旨在探讨在等长NHE过程中，在保持力臂相等的情况下，肌肉长度变化对腘绳肌肌电活动的影响。
交叉研究设计。
16名男性志愿者进行两种类型的传统NHE，一种是膝盖着地（NHE），另一种是将腿放在小腿板的倾斜面上（NHEB）。为了比较传统NHE和倾斜NHE，一名检查者通过将小腿保持在小腿长度的77%和94%处标记的点上，计算出膝关节处的力臂相等。四个亚组包括：1）NHE - 77%，2）NHE - 94%，3）NHEB - 77%，和4）NHEB - 94%。在股二头肌长头（BFlh）、半腱肌（ST）及相关代偿肌肉处测量腘绳肌的肌电活动。均方根（RMS）数据被标准化为最大等长值的百分比（标准化肌电图[nEMG]）。使用SPSS软件进行Tukey事后检验对显著的主效应结果进行跟进，统计学显著性设定为p < 0.05水平。
NHE - 77%的BFlh肌电活动值分别显著高于NHE - 94%（p = .036）和NHEB - 77%（p < .001），而NHE - 77%期间的ST仅在NHEB - 77%中显著更高（p < .001）此外，对于BFlh（p < .001）和ST（p < .001），NHEB - 94%均显著大于NHEB - 77%。
这些结果表明，在北欧式腿弯举运动中，当腘绳肌被拉长时，其肌电活动会降低。
3级。
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