prestigious assignments as computerized biomechanical analyses of whole teams such as the Dallas Cowboys, and serves as director of computer science and biomechanics for the United States Olympic Committee.

The rush at the force plate I have made is done to compare my running characteristics with those of my 25-yearold son, Mark. Mark is in contact with the plate for .4 seconds too long. He stopped at the plate, not an uncommon practice for people getting used to the unnatural laboratory environment. Even Bill Rodgers had to get used to it when C.B.A. tested not Bill's running style but the shoes he was wearing. Mark has a breaking force of only 47 pounds because he fails to stride through. His pushing force is, accordingly, slight-21 pounds. And he has a lateral force of 47 pounds because his body is not quite positioned over his foot. I come through with a striking force of 374 pounds (well over twice my 165pound weight), and no breaking force at all because I follow through. I am on the plate only 228 milliseconds, and I exhibit 59 pounds of pushing force that almost smashes me into the wall.

To get a total picture of the myriad forces in action while running, Gideon

says these experiments should be filmed at a rate of 200-300 frames per second. His computers can convert that picture into stick figures that show on the display console just what is happening to the entire organism and its components every millisecond. But that kind of total analysis could take as long as a week. For such a complete analysis with force plate, computers, high-speed movies and stickfigure conversions of sequential energy expenditure, C.B.A. charges $1,500. Gideon expects to trim this fee in California because he'll have lower overhead. Business thus far is good. Each of the two labs is staffed by six scientists with backgrounds in computers, exercise physiology and allied fields.

To create this program, it was first necessary for Ariel to interface diverse equipment from different manufacturers with devices built by C.B.A. itself, such as its "sneaker-beater." This jointed steel leg can have any kind of shoe fitted to it. Knowing the mass of the leg and how it's distributed, C.B.A. staffers can assess the wear and other performance characteristics of the shoe by making it hit on a test surface at any point along the sole. This is an important breakthrough be

cause, by simulating actual running, the sole goes beyond static-load testing,

where constant pressure is applied to a

material to find out how much it compresses or when it reaches its breaking point.

But 'while the rapidly applied dynamic load of running deforms or breaks shoe materials sooner than a static load does, that dynamic load varies too much from runner to runner, and even from run to run in the same runner, to be dependable. The sneaker-beater takes care of that problem by smoothing out these variables to make the results more predictably uniform. Its ram is attached to a displacement transducer so that it can measure both force and displacement simultaneously. That gives C.B.A. accurate measurements of the actual behavior of the material, shows how it absorbs energy and how it recovers, spells out its stiffness and energy-loss and so on. All this information is reduced to usable form by the computer for instant visual evaluation on its display console.

The force plate can measure force in three coordinate dimensions-vertical, horizontal and longitudinal. It also measures twist or rotation. The plate is designed around special piezo-electric crystals that are built up in layers with the grain going in different directions. The direction of the grain determines which force it will measure. With the sensitivity turned up, the force plate can detect the presence of a fly.

Asked about the improvements he expects in running shoes over the next decade, Ariel climbs up on an ordinary metal folding chair and jumps three times in a row from the chair to the force plate. The first jump is onto the bare surface, and the computer shows he hit with a force of 493 pounds, more than double his body weight of 218. Next he jumps onto an athletic-mat material made by Dow called Epifoam, a tough and resilient synthetic about an inch thick, and generates a force of 488 pounds. When he jumps the third time onto yet another artificial foam of the same thickness but supposedly even more shock-absorbing than Epifoam, the computer display panel reads 504 pounds-more force than was transmitted to Ariel's body when he jumped onto the naked hardness of the force plate. For further demonstration, he drops a calculus textbook three times onto the same sequence of surfaces, and from the same height, and gets force readings of 63, 136 and 116 pounds, respectively.

"What does that tell us?" asks Ariel rhetorically in his Israeli accent. "With the book we saw a drastic difference. With the human body, we don't see a drastic difference. The reason the force will bt' approximately the same no matter how often I jump, or what I jump on, is that we have a filtering system inside our

THE LONELINESS OF THE MIDDLE-DISTANCE JOGGER

0.00 The tube socks,

the shorts, the supporter, the T-shirt,

the headband, even the shoes

all are (mostly) white.

0.25 Breathing easily, gliding at first,

hardly touching earth. Muscles stretching, contracting, smooth as poured oil.

0.75 Sweat now all over, the legs driving,

the arms pumping, the heat pulling

the body's poisons out

to shine on the surface of the skin.

1.50 Teenagers with flat stomachs grin, look askance, catcall,

don't know what asceticism means.

2.00 The fat man

laughing in the passing car eats potatoes fried in grease. One day I'll pass him by as he pants up a stair. He won't laugh then.

2.50 Sprinting now, the home stretch. Move over Lasse Viren.

1.00 Breathing is not so easy, but not yet ragged. Confidence

Is

the key.

3.00 A short walk

back homea new man

inside a salty rime, drying in the breeze.

BILL CRIDER

THE RUNNER March 1980