Schilling Nadja, Carrier David R
Institute of Systematic Zoology and Evolutionary Biology, Friedrich-Schiller-University, Erbertstrasse 1, Jena 07743, Germany.
J Exp Biol. 2009 Apr;212(Pt 7):1053-63. doi: 10.1242/jeb.020248.
In mammals, the epaxial muscles are believed to stabilize the trunk during walking and trotting because the timing of their activity is not appropriate to produce bending of the trunk. To test whether this is indeed the case, we recorded the activity of the m. multifidus lumborum and the m. longissimus thoracis et lumborum at three different sites along the trunk (T13, L3, L6) as we manipulated the moments acting on the trunk and the pelvis in dogs trotting on a treadmill. Confirming results of previous studies, both muscles exhibited a biphasic and bilateral activity. The higher burst was associated with the second half of ipsilateral hindlimb stance phase, the smaller burst occurred during the second half of ipsilateral hindlimb swing phase. The asymmetry was noticeably larger in the m. longissimus thoracis et lumborum than in the m. multifidus lumborum. Although our manipulations of the inertia of the trunk produced results that are consistent with previous studies indicating that the epaxial muscles stabilize the trunk against accelerations in the sagittal plane, the responses of the epaxial muscles to manipulations of trunk inertia were small compared with their responses when moments produced by the extrinsic muscles of the hindlimb were manipulated. Our results indicate that the multifidus and longissimus muscles primarily stabilize the pelvis against (1) vertical components of hindlimb retractor muscles and (2) horizontal components of the hindlimb protractor and retractor muscles. Consistent with this, stronger effects of the manipulations were observed in the posterior sampling sites.
在哺乳动物中，轴上肌被认为在行走和小跑时稳定躯干，因为其活动时间不适合产生躯干弯曲。为了验证情况是否确实如此，我们在跑步机上小跑的狗身上，沿着躯干的三个不同部位（T13、L3、L6）记录了腰多裂肌和胸腰最长肌的活动，同时我们操纵作用于躯干和骨盆的力矩。与先前研究结果一致，这两块肌肉均表现出双相和双侧活动。较高的爆发与同侧后肢站立期的后半段相关，较小的爆发发生在同侧后肢摆动期的后半段。胸腰最长肌的不对称性明显大于腰多裂肌。尽管我们对躯干惯性的操纵产生的结果与先前的研究一致，表明轴上肌可稳定躯干以抵抗矢状面内的加速度，但与后肢外在肌产生力矩时轴上肌的反应相比，轴上肌对躯干惯性操纵的反应较小。我们的结果表明，多裂肌和最长肌主要稳定骨盆以抵抗（1）后肢牵缩肌的垂直分量和（2）后肢前伸肌和牵缩肌的水平分量。与此一致的是，在后部采样部位观察到操纵的效果更强。
