The passage implies that reversing the muscle-bone movement used to bend an arm requires the use of different muscles.

这篇文章暗示我们手臂肌肉骨骼的回动的动作需要利用不同的机肉来完成。

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Salomon Smith Barney, the securities arm of financial services company Citigroup, recently said it would offer Internet trading later this year, reversing a previous policy of limiting clients' Internet access to research and portfolio checking.

BBC: News | Your Money | Merrill Lynch moves online