Pietrosimone Brian G, Hammill Robert R, Saliba Ethan N, Hertel Jay, Ingersoll Christopher D
Exercise & Sport Injury Laboratory, University of Virginia, Charlottesville, Virginia, USA.
Am J Phys Med Rehabil. 2008 Feb;87(2):100-8. doi: 10.1097/PHM.0b013e31815882e0.
The purpose of the study was to compare the central activation ratio (CAR) of eccentric contractions to isometric contractions at 30 and 70 degrees of knee flexion.
A repeated-measures design was used. CARs were measured at 30 and 70 degrees of knee flexion in 16 healthy subjects during both eccentric and isometric modes of contraction. CARs were measured using the superimposed burst technique.
Isometric CARs at 30 degrees (0.88+/-0.069) of knee flexion were significantly higher (P<0.001) than at 70 degrees (0.77+/-0.116). Eccentric CARs were significantly higher (P=0.013) at 70 degrees (0.87+/-0.085) of knee flexion compared with 30 degrees (0.8+/-0.09). At 30 degrees of knee flexion, isometric CARs were significantly higher (P=0.003) than eccentric CARs. At 70 degrees, eccentric CARs were higher (P<0.001) when compared with isometric CARs.
Our results provide evidence that isometric measures at a single joint angle are not sufficient in generalizing activation of an entire muscle group for dynamic movements. CARs are significantly affected by joint angle and mode of contraction.
本研究旨在比较膝关节屈曲30度和70度时离心收缩与等长收缩的中枢激活率（CAR）。
采用重复测量设计。在16名健康受试者进行离心和等长收缩模式时，测量膝关节屈曲30度和70度时的CAR。使用叠加脉冲技术测量CAR。
膝关节屈曲30度（0.88±0.069）时的等长CAR显著高于70度（0.77±0.116）时（P<0.001）。膝关节屈曲70度（0.87±0.085）时的离心CAR显著高于30度（0.8±0.09）时（P=0.013）。在膝关节屈曲30度时，等长CAR显著高于离心CAR（P=0.003）。在70度时，离心CAR高于等长CAR（P<0.001）。
我们的结果表明，单一关节角度的等长测量不足以概括整个肌肉群在动态运动中的激活情况。CAR受关节角度和收缩模式的显著影响。
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