The piriformis muscles, strong external rotators of the thigh, attach to the sacrum and the femur. Stretching them can increase S-I joint instability.
梨状肌是附着在骶骨和大腿骨上的强大的回旋肌，对他们的拉伸有损于骶髂关节的稳定性。
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Regular U. S. -South Korea joint military exercises, most recently in July, have the same effect.
美韩定期联合军事演习，最近一次是在七月，也有着同样的效果。
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And strengthening the muscles around the S-I joint so as to prevent future problems can be accomplished by practicing simple backbends and standing poses.