In horse riders if this muscle is tight it prevents the rider being able to stretch the leg back and keep the heel in alignment with the shoulder.

如果骑手的腰肌紧张会有碍他向后拉伸腿并保持足跟与肩形成一条水平线。

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The biggest challenge of survey and alignment is the soft groundwork and the tight positioning requirement for Shanghai Synchrotron Radiation Facility.

上海光源在准直测量方案设计中面临的最大挑战来自于松软地基及高精度的定位要求。

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