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TEACHING GUIDES


GOING TO EXTREMES: Ultimate Speed

(Running Time: 10:54)



The cheetah and the pronghorn antelope are the world's fastest land animals, but each achieves its success in locomotion because of very different biomechanics. The cheetah is a sprinter, built for speed with a flexible body and a large stride. By contrast, the pronghorn's body is built for endurance and long distances; it has evolved an aerobic ability that enables it to utilize oxygen at a very high rate. Both the cheetah and the pronghorn have been clocked at speeds higher than 60 mph.

Curriculum Links
"Do the Locomotion . . ."
Activity 1: Calculate VO2 Max
Activity 2: Biomechanics of Running
For Further Thought



CURRICULUM LINKS


BIOLOGY

blood gases,
respiration
GENERAL
SCIENCE


mammals,
vertebrates
LIFE
SCIENCE


life processes,
respiration
PHYSICAL
SCIENCE


force plate
analysis, gases

PHYSICS


acceleration,
velocity




"DO THE LOCOMOTION . . ."

Researchers interested in the physiology of locomotion look at how the body's systems - respiratory, cardiovascular, musculoskeletal - work when animals move. As you see on FRONTIERS, physiologists use different tools and devices to study the science of running. Gas analyzers of O2 and CO2 concentrations and flowmeters can determine how efficiently an organism uses oxygen; high-speed videos record and analyze components of movement. The same techniques can be applied to human physiology and fitness. You can set up your own research activities to find out more about the physiology and biomechanics of locomotion.



ACTIVITY: CALCULATE VO2 MAX

The two fastest land animals, the pronghorn and cheetah, have evolved different solutions to the need for speed. Each animal is perfectly designed to run at top speed. One difference is in the ways the two use oxygen. The cheetah, like any sprinter, is anaerobic, while the pronghorn relies on aerobic endurance, similar to marathon runners.

Several tests have been developed to measure aerobic capacity in people and in animals. A popular test measures VO2 (volume of oxygen) max - the more efficiently the oxygen is used, the more fit the runner. The higher the VO2 max, the greater the aerobic capacity. The longer the run, the more accurate the measurement. Less than a mile is anaerobic running, not aerobic.

Physiologists have found a high aerobic capacity or ability to use oxygen in the pronghorn. As you see on FRONTIERS, physiologists monitor the O2 and CO2 concentrations in expired gases from the pronghorn.

You can measure VO2 max yourself, by following these steps. Work with the physical education teacher or a track coach. You may want to ask for volunteers from various sports teams or set aside a block of time for a special physical education/science project. Non-runners can handle the timing and calculations for the runners.

MATERIALS
  • stopwatch
  • calculator
  • writing materials
  • graph paper

OBJECTIVE

Collect and analyze data to calculate human aerobic capacity.

PROCEDURE

Use this equation to calculate VO2 max for a distance of one mile: VO2 max = 133.61 - (13.89 x time)

Time is equal to the number of minutes it takes to run one mile. VO2 max is usually given in milliliters of oxygen per kilogram of body weight per minute (ml/kg/min). This equation, from Inside Running: Basics of Sports Physiology by David Costill, is just one example of many prediction equations. For a two-mile test, use: VO2 max = 128.81 - (5.95 x time).

QUESTIONS

  1. Graph the data you collect and examine it in different ways. For example, does VO2 max differ by age or gender? Does VO2 max differ among students involved in different sports?

  2. VO2 max can be influenced by exercise. What kind of exercise might help improve VO2 max?

  3. Why might we see more variation in aerobic capacity in humans than in animals?

  4. Compare and contrast the physiology and biomechanics of the cheetah and pronghorn.


ACTIVITY: BIOMECHANICS OF RUNNING

When animals want to run faster, they increase either their stride rate or stride length. As you see on FRONTIERS, measuring the stride of a galloping pronghorn is challenging! Cheetah

A stride is a complete movement from the point of one foot striking the ground, leaving it, then striking the ground again. Stride length is the distance traveled in one stride. A horse has a maximum stride length of about seven meters, a stride rate of about 2.25 strides/second and a top speed of about 70 km/hr. A cheetah, which is much smaller than a horse, has a stride length that is about the same as that of the horse; but the cheetah has a stride rate of about 3.5 strides/second and a top speed of about 110 km/hr. Where does the difference in speed come from? Consider the cheetah's physiology as explored in Activity 1: Calculate VO2 Max. Teaching Guides Header
Physiologists studying the mechanics of movement look at how anatomy contributes to speed by running animals at different speeds and filming them. They use high-speed cameras that can film at speeds greater than 1,000 images per second. Even though a video camera can shoot only 30 images per second, not fast enough to capture the details researchers need to see, you can use it to begin studying the biomechanics of running.

MATERIALS
  • video camera
  • meter stick
  • writing materials
  • graph paper

OBJECTIVE

Find out how different speeds affect stride rate and length.

PROCEDURE

  1. Position the video camera (an 8mm camera is best) in a well-lit area and against a backdrop that will let you capture a runner passing in front of the camera. Make sure you keep a detailed research journal with information on time, date and details of the data collection. You should also record the position of the camera setup so you can duplicate it if you have to take down your equipment.

  2. Frame the picture so that you can capture about two full strides without having to move the camera while your subject is running.

  3. Place a meter stick or mark the background with meter increments to give you a frame of reference to measure. To get a time reference, have the camera's time and date stamp feature turned on.

  4. Start your camera and have the subject walk slowly in a straight line past the camera. Record at least two trials.

  5. Next have your subject run at a jogging pace and record two trials. Repeat this at faster paces until, for the last trial, you have the subject sprint in front of the camera.

  6. Once you've collected your data, examine the video to see how stride length and stride rate vary with pace. You may want to set up a data table to record the pace, stride length and stride rate.
QUESTIONS

  1. How do stride rate and stride length vary between males and females? Among runners of different ages?

  2. Set up experiments that study the stride rate and length of different animals, or of different breeds of animals. How do they compare?

EXTENSIONS

  • If your videotape player has a pause feature, you can stop the video at key times to trace the outline of the legs in a stride. Try to superimpose the bones of the leg over your drawing. What is the movement of the bones in the leg and foot over the course of a stride cycle?

  • Reset your camera to get a close-up of the foot during running. How does the movement of the foot vary at different speeds? Does a different part of the foot hit the ground first? Does this vary among different people?

  • Research other running animals. What bones do they use to run? How do they differ from the bones in a human's leg and foot? How does the ankle spur and bone structure help pronghorn run?

  • If you have access to a software program like Avid Cinema, try making a movie of animals or people running, perhaps for your school's Web page, or just for fun.

  • You can measure your VO2 max on a treadmill. See Bicycling Medicine - Cycling Health, Fitness " Injury Explained by Arnie Baker, M.D.



FOR FURTHER THOUGHT

  • Cheetah and other large mammals inhabited parts of North America until the end of the Pleistocene era, about 10,000 years ago. Find out where they lived and why they died out in these regions.

  • The cheetah is greatly endangered. Find out how many cheetah are living, where they live and the reasons for their critical status.

  • The pronghorn's speed may be an evolutionary adaptation in response to a predator chasing it. Today there is no creature living in the pronghorn's habitat that is capable of pursuing the chase. So why do pronghorn continue to run so fast? Some scientists have suggested that they are being chased by "ghosts" of predators. In other words, according to this theory pronghorn exhibit behavior appropriate for the wild but no longer necessary for survival. Can you find other examples of relict behavioral adaptations?


CREDIT: These activities were contributed by Jamie Larsen, a science teacher and Tufts University Wright Fellow currently living near Sedona, Arizona.





 

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