As you slowly return to the starting position , turn your palms toward the ceiling , flex your arms and curl the dumbbells in toward your shoulders .
当慢慢回到原位置时，手掌朝上，弯曲手臂，朝肩部方向运动哑铃。
Scientists have long speculated that ocean waves could cause an ice shelf to flex and break , but this is the first time researchers have observed a tsunami having this effect .
When a knife cuts your skin , it leaves a relatively clean cut compared to paper , which will flex a little and do more microscopic damage to the skin .
During yawning , the walls of the maxillary sinuses ( located in the cheeks on each side of the nose ) flex like bellows and help with brain cooling , according to the researchers .
这两位研究人员表示，在打哈欠时，上颌窦的壁部（位于鼻子两边的脸颊上）像风箱一样弯曲，帮助大脑降温。
The severing at these points causes nerve damage that makes the wrist flex and the fingers curl up in the manner of a waiter taking a backhanded tip .
