c

Race walking shares many fitness benefits with running, research shows, while most

likely contributing to fewer injuries. It does, however, have its own problem.

Race walkers are conditioned athletes. The longest track and field event at the Summer

Olympics is the 50-kilometer race walk, which is about five miles longer than the marathon.

But the sport's rnules require that a race walker's knees stay straight through most of the leg

swing and one foot remain in contact (接触) with the ground at all times. It's this strange form

that makes race walking such an attractive activity, however, says Jaclyn Norberg, an assistant

professor of exercise science at Salem State University in Salem, Mass.

Like running, race walking is physically demanding, she says. According to most calculations,

race walkers moving at a pace of six miles per hour would bum about 800 calories (卡路里)

per hour, which is approximately twice as many as they would bum walking, although fewer

than running, which would probably bumn about 1,000 or more calories per hour.

However, race walking does not pound the body as much as running does, Dr. Norberg

says. According to her research, runners hit the ground with as much as four times their body

weight per step, while race walkers, who do not leave the ground, create only about 1.4 times

their body weight with each step.

As a result, she says, some of the injuries associated with nunning, such as runner's knee,

are uncommon armong race walkers. But the sport's strange forn does place considerable stress

on the ankles and hips, so people with a history of such injuries might want to be cautious in

adopting the sport. In fact, anyone W ishing to try race walking should probably first consult a

coach or experienced racer to learn proper technique, she says. It takes some practice.

[单选题]

[单选题]

[单选题]

[单选题]