bodies. When you reach a certain threshold of force, some joint is going to give. It makes no difference what you jump on, the force is going to be about the same, within 50 pounds. If you run faster, of course, the force will be higher for the same speed. That's why I'm jumping, because I'm falling at the same speed.

"Now I'll try to fall a little more carefully," he says, and he jumps a fourth time, but more delicately, landing on his toes and springing lightly off the force plate. Reading this time: 456 pounds. "So I knock off 30-40 pounds just by using my body better. So the story in running is much more drastically how you run than what you run on-or even what you run in. It's that filtering mechanism in the body that the people in the shoe companies fail to realize. They think that by making a shoe with a little more heel or by making it a little thinner, it will make a drastic difference. No, it's how the body accommodates. If I fall really hard, it will add maybe 100 pounds of force. It depends on how much I give in my knees.

"When the body reaches a certain threshold, the knee gives. If the knee is too hard, the hip gives. If the hip doesn't give, you reach a certain point where you crush yourself. You jump from a plane with no parachute."

Pointing to his sneaker-beater, Ariel says, "If we use this mechanism, we have a drastic difference between shoes of different materials, because there is no filter here. There is no dumping. It's steel. Metal. Not flesh and joints. In the human body you have a lot of dumping. So anybody who says one shoe is 100 times better than another shoe is full of baloney. One runner might like this shoe, another might like that shoe."

Was there any one thing Ariel might hope to see developed to make future running shoes more helpful for the runner across the board? "We would like to produce more shock absorption in the shoe for everybody," he pauses, "for long distance. For certain athletic events, you don't want shock absorption. You want all the force to go right into the leg. That's why sprinting shoes are very hard. But you are taking risks. You may have injuries. You don't want shock absorption when you are sprinting full blast in the Olympics. But you don't train all the time sprinting full blast."

Emphasizing that different people want different things in a shoe-"your average runner wants something (Iifferent, than a runner training for competition, your jogger has different. running

characteristics than someone training for a marathon, and when you train for a marathon you have different characteristics from when you actually run in a marathon."-Ariel concludes firmly, "There isn't one shoe for everybody, and there never will be. An `average shoe' is by definition a shoe that fits nobody, because people will be to one side of the line or the other, never on it."

This iconoclast of the computer, who admits he makes "lots of enemies by telling people where they're wrong," has poured time and money into research and development of prototypes for running shoes. One has an inflatable insole and a tiny appendage at the back of the heel to which he affixes a COs hand cylinder to pump up the insole with a quick puff. He says they used too much gas at first and got in effect a balloon, with too much sway. After checking many runners on the force plate, C.B.A. redesigned the insole with air pockets in different places and narrow alleys separating them into a pattern, waffle-fashion. They got so much variation among the runners, though, that Ariel thinks inflatable insoles will always have to be customized.

Another future shoe is a sleek red sprinting model with a white plastic wedge under the arch, its razor-thin forward edge flush with and extending back from the sole, and its flat rear edge ending where the non-existent heel would have begun. "We tried to design this shoe so that when you sprint, you would apply force at the proper angle," Ariel explains. "This is the way you run in sprinting, so the wedge helps you push off against the surface for maximum force at leap-off."

A third future shoe is a weightlifting shoe with a variable heel that lets the athlete achieve greater mechanical advantages for different weights at different heights by adding or removing leather sections at the heel. Yet a fourth experimental model is a track shoe Ariel is using to determine whether spikes, instead of helping a runner, might actually interfere with performance. "We don't know if you need all these spikes, especially with artificial surfaces. We are finding out. We are also finding out maybe you shouldn't prevent rotation."

Gideon Ariel's C.B.A. has no peer, he claims, "and I travel all over world. There is nothing like it anywhere." He feels the day has passed when athletes could win Olympic gold medals on sheer talent., and that. if we apply his kind of computerized analysis and training,

"There is no limit to what we can achieve." He points out that the field is wide open, that there's room for "a hundred operations like ours" to teach golfers how to add 30 yards to a drive, place kickers to boost yardage, tennis players to belt out faster serves, young athletes to find their way earlier to excellence in sports, and runners to use their individual characteristics more productively.

While Ariel takes a dim view of most podiatric practice because, he believes, the podiatrist sees only the results of physical activity, never the activity itself, and rarely has the opportunity to measure that activity as precisely as C.B.A.'s equipment can, Ariel has nonetheless teamed up with San Francisco podiatrist Jim Malone to develop a trademarked Shoe Scan data questionnaire. The runner answers the questions, sends it to C.B.A. with $15 and gets a computer printout within four weeks that lists recommended shoes that fit the individual subscriber's personal needs and shoe stores that carry those shoes, a $2 certificate redeemable at participating stores, recommendations for shoe care and information to help find manufacturer's defects. The Shoe Scan project (360 College Avenue, Amherst, Massachussetts 00112) will even take credit cards and boasts, "We'll give you a run for your money."

Ariel says that even today materials vary so widely in memory, shock absorption and wear characteristics that it would be impossible to evaluate them meaningfully without a computer. He thinks shoe materials in the coming years will be "like nothing we have now, and will simulate the characteristics of air inside the shoe. They will also be lighter and very hard. They could wear a lot longer too, but most shoe companies don't want to see shoes wear too well."

Concerned as he is with "the way the foot behaves inside the shoe," Ariel envisions "cafeterias" capable of assembling shoe components on a customized basis as perhaps the runner's best hope of getting the correct shoe a decade from now. "Maybe they'll need to have a computerized force plate in every store," he says, "but they'll also need personnel who know how to interpret what the equipment is saying. Otherwise it's guessing."

Then, in a rare departure from his party line of the marriage of machine and mass, Ariel confessed: "The right. shoes for the individual runner may help, bul, only proper training and conditioning ran solve the underlying problems." IFINISHI