英语听力文摘 English Digest 668 为何一些人是双关节？

 　　Why Are Some People Double-Jointed?

　　Can you bend your thumb backwards² until it touches your wrist? If you join your hands behind your back, can you lift them over your head without letting go?

　　If you can, you might be what some people call “double-jointed.” But, A Moment of Science wonders, how could anyone have double joints³?

　　Range Of Motion

　　Double-jointed people don’t really have two joints. Any joint¹, such as the thumb joint or the shoulder, can be called “double-jointed” if the tendons and ligaments surrounding the joint allow a wider range of motion than is usual.

　　Joints are created whenever 2 adjacent bones meet. They have fibrous bands of connective tissue called ligaments that stabilize⁴ the joint. Connective tissues also form the tendons that join the bones to the muscles.

　　Ligaments and tendons usually restrict the movement of the joint, but in some people, these normally restrictive tissues can be quite flexible and allow the extra movement we call “double-jointed.” Practice can increase a joint’s natural flexibility⁵ just the way stretching can increase your muscles’ flexibility.

　　Flexibility

　　While flexible joints are very useful to contortionists, some joints can become so loose that they are unstable⁶. This allows the bones of the joint to slip out of their sockets⁷ and can be very damaging.

　　Strengthening the muscles around the joint can stabilize it and still allow you to show off your trick joint at parties.

1 joint   

adj.联合的，共同的；n.关节，接合处；v.连接，贴合

参考例句：

• I had a bad fall,which put my shoulder out of joint.我重重地摔了一跤，肩膀脫臼了。
• We wrote a letter in joint names.我们联名写了封信。

2 backwards   

adv.往回地，向原处，倒，相反，前后倒置地

参考例句：

• He turned on the light and began to pace backwards and forwards.他打开电灯并开始走来走去。
• All the girls fell over backwards to get the party ready.姑娘们迫不及待地为聚会做准备。

3 joints   

接头( joint的名词复数 )； 关节； 公共场所（尤指价格低廉的饮食和娱乐场所） （非正式）； 一块烤肉 （英式英语）

参考例句：

• Expansion joints of various kinds are fitted on gas mains. 各种各样的伸缩接头被安装在煤气的总管道上了。
• Expansion joints of various kinds are fitted on steam pipes. 各种各样的伸缩接头被安装在蒸气管道上了。

4 stabilize   

vt.（使）稳定，使稳固，使稳定平衡；vi.稳定

参考例句：

• They are eager to stabilize currencies.他们急于稳定货币。
• His blood pressure tended to stabilize.他的血压趋向稳定。

5 flexibility   

n.柔韧性，弹性，（光的）折射性，灵活性

参考例句：

• Her great strength lies in her flexibility.她的优势在于她灵活变通。
• The flexibility of a man's muscles will lessen as he becomes old.人老了肌肉的柔韧性将降低。

6 unstable   

adj.不稳定的，易变的

参考例句：

• This bookcase is too unstable to hold so many books.这书橱很不结实，装不了这么多书。
• The patient's condition was unstable.那患者的病情不稳定。

7 sockets   

n.套接字，使应用程序能够读写与收发通讯协定(protocol)与资料的程序( Socket的名词复数 )；孔( socket的名词复数 )；（电器上的）插口；托座；凹穴

参考例句：

• All new PCs now have USB sockets. 新的个人计算机现在都有通用串行总线插孔。
• Make sure the sockets in your house are fingerproof. 确保你房中的插座是防触电的。 来自超越目标英语 第4册