(二十一)

According to some scientists, high－risk sports can be particularly valuable for certain types of people. Such activities help them to learn that being frightened doesn't mean they have to lose control. The recent fashion for jumping from bridges fastened to a length of elastic(有弹性的)rope, known as "bungee jumping", has now been tried by over one million people worldwide, and interest in it is continuing to grow.
Before the special elastic rope tightens(拉紧)around them, jumpers reach speeds of nearly 160 kilometers per hour. First－timers are unusually too frightened to open their mouths, and when are finally lowered safely to the ground, they walk around with broad smiles on their face, saying repeatedly how exciting it was. However, for some people, it is only the embarrassment(难堪)of refusing to jump at the last minute that finally persuades them to conquer their fear of heights and push themselves off into space.
简析：说明文文体，阐述高风险运动对某些特定人群很有价值。