Department of Physical Education, National Defence Academy , Kanagawa, Japan.
J Sports Sci Med. 2009 Dec 1;8(4):548-52. eCollection 2009.
The purpose of present study was to compare the effect of Ia afferent attenuation on the activity of alpha motor neuron (MN) during concentric and eccentric action. Eight male subjects were enrolled in the present study. The experiments consisted of two sessions of MVC measurements, since all subjects performed both maximal concentric and eccentric action. EMG signals were simultaneously measured. To establish the baseline of strength, subjects were asked to perform MVC of knee extension in each session. After finishing the measurements, 20 min of vibration stimulation was applied. Immediately after finishing vibration stimulation, the MVC and AEMG were again measured. The means of MVC for concentric knee extension at pre and post- vibration stimulation were 192.2 ± 49.3 Nm and 162.3 ± 47.9 Nm, respectively. The means of MVC for eccentric knee extension at pre and post-vibration stimulation were 299.7 ± 77.0 Nm and 247.3 ± 88. 6 Nm, respectively. Two-factor repeated ANOVA detected significant differences in the MVC. Both main effects for pre-post condition (F(1,7)=, p = 0.0033) and action (F(1,7)=26.35, p = 0.0013) were noted. No interaction effect (action x condition) was noted. The means of AEMG (vastus lateralis (VL), vastus medialis (VM), rectus femoris (RF)) at pre and post -vibration stimulation were decreased. Two-factor repeated ANOVA detected significant differences in AEMG (VM and VL). Both main effects for pre-post condition (VL;F(1,7)=7.27, p = 0.0308, VM; F(1,7)=9.55, p = 0.0175) and action (F(1,7)=12.40, p = 0.0097) were noted in the VL and the VM but not in the RF. Furthermore, significant interaction (action x condition) effect was noted in the VM (F(1,7)=7.03, p = 0.0328) but not in the VL. The MVC and the EMG activity of the VL in response to the prolonged vibration stimulation were significantly reduced in eccentric contraction over concentric contraction. These results represented that a deactivation effect on the alpha MN of the VL during eccentric action was greater than that of concentric action. Key pointsA deactivation effect on the alpha motor neuron of the vastus lateralis during eccentric action was greater than that of maximal concentric action.
本研究旨在比较 Ia 传入神经阻滞对向心性和离心性收缩时运动神经元（MN）活性的影响。本研究纳入了 8 名男性受试者。实验包括两次最大等长收缩测量，因为所有受试者都进行了最大向心性和离心性收缩。同时测量肌电图信号。为了建立力量的基线，要求受试者在每次试验中进行膝关节伸展的最大等长收缩。完成测量后，进行 20 分钟的振动刺激。振动刺激结束后立即再次测量 MVC 和 AEMG。振动刺激前和后向心性膝关节伸展的 MVC 平均值分别为 192.2 ± 49.3 Nm 和 162.3 ± 47.9 Nm。振动刺激前和后离心性膝关节伸展的 MVC 平均值分别为 299.7 ± 77.0 Nm 和 247.3 ± 88.6 Nm。双因素重复方差分析检测到 MVC 的显著差异。前-后条件（F(1,7)=, p = 0.0033）和动作（F(1,7)=26.35, p = 0.0013）的主效应均有统计学意义。未检测到动作 x 条件的交互效应。振动刺激前和后，AEMG（股外侧肌（VL）、股内侧肌（VM）、股直肌（RF））的平均值均降低。双因素重复方差分析检测到 AEMG（VM 和 VL）的显著差异。前-后条件的主效应（VL：F(1,7)=7.27, p = 0.0308，VM：F(1,7)=9.55, p = 0.0175）和动作（F(1,7)=12.40, p = 0.0097）在 VL 和 VM 中均有统计学意义，但在 RF 中无统计学意义。此外，在 VM 中检测到显著的交互（动作 x 条件）效应（F(1,7)=7.03, p = 0.0328），但在 VL 中未检测到。VL 对延长振动刺激的反应中，离心收缩时的 MVC 和 EMG 活动明显低于向心性收缩。这些结果表明，VL 的 alpha MN 在离心收缩时的去激活效应大于向心性收缩。关键点VL 在离心收缩时的 alpha MN 去激活效应大于最大向心性收缩。
