Get the jump on soles: here's a peek at how sneaker designers slip science into your soles - includes a short experiment on jumping in sneakers

Science World, Feb 23, 1998 by Damian McNamara

Here's a peek at how sneaker designers slip science into your soles.

What do "octopus suckers," "herringbones," and "nubby cobbles" have in common? They're state-of-the-art sneaker designs!

Check out the soles of some hot new sneaker models. New Reebok basketball soles sport air-filled pods that look like the suction cups on an octopus. Fila Grant Hills and Nike Zoom Air Pros boast zany patterned soles that make use of herringbone, or zigzag, traction grooves. Fila

Signatures and Nike Air Zooms feature knobby bottoms that resemble big goose bumps.

What's the sole story? In the cutthroat sneaker market, famous name brands are blending high-flash design with high-tech biomechanics (the mechanics of body action) to grab your interest--and your dollars. After all, in 1996 Americans spent $1.2 billion on 22 million pairs of basketball shoes, according to the National Sporting Goods Association. But the real question is: Is sneaker design science or just jazzy marketing hype? Will a $100-plus pair of sneakers make you run faster or soar higher than good old cut-rate high-tops?

SNEAKER LAB

At Reebok's Human Performance Engineering Lab in Stoughton, Massachusetts, 30 sneaker scientists and engineers videotape star athletes sprinting, shooting hoops, and wielding tennis rackets. "That's the fun stuff from my perspective," says Spencer White, Reebok's research and engineering director.

The lab looks like a high-tech gym with a bank of computer tables and measuring equipment that surround a half-basketball court and a 30-m (100-ft) running track. Researchers swap Astro Turf (artificial grass) for the smooth wood floor when they seek to mimic tennis courts. White and his team review high-speed videos frame-by-frame to examine the motion of athletes' feet upon impact, when the feet apply force to the ground (the ground returns an equal amount of force to the foot, according to the laws of physics).

With every step, your feet--each with its 26 small bones and many joints, as well as tendons and muscles--bear the full weight of your body. When you walk, your foot applies 1.25 to 1.5 times your body weight to your heel. When you run, the force increases to 2 to 3 times your weight. And when you leap to spike a volleyball or slam dunk a basketball, your heel has to absorb a force up to 10 times your body weight. "For nearly 136-kg (300-lb) Shaquille O'Neal, 10 times his body weight equals a ton and a half of pressure," says White.

Sneaker scientists use a sensor called a force plate to measure exactly how the foot applies pressure on the ground as it moves from heel to toe. Then they engineer athletic soles to absorb the shock of feet by spreading out that force.

Reebok researchers spent five years developing their latest sole-technology--the DMX Series 2000. The "octopus suckers" are actually 10 chambers packed with air-five in the heel and five in the forefoot. As you walk or run, air-filled cushions shift air from heel to toe to stabilize your foot joints and reduce the risk of injury from impact. "You can actually feel air shifting back and forth under your foot, like a waterbed," says White.

But don't get too excited about the look of Reebok's new technology. "Designs are constantly changing," White cautions. "Every model has to meet performance standards, but the look has to be different every time."

TOUGH COMPETITION

Two of Reebok's competitors, Fila and Nike, bare their soles quite differently. Fila's Grant Hill models (designed for the ace basketball player) and Nike's Zoom Air Pros (inspired by Michael Jordan) rely on a flatter surface with a traditional herringbone pattern of thinly-spaced grooves--the hallmark of basketball and tennis shoes. The flatter surface and thin grooves allow more contact and traction, or adhesive grip, between the player's foot and the smooth basketball court. They also increase friction, or rubbing action between surfaces, so basketball players can zoom over the court without fear of slipping or sliding--on their rears.

For joggers and runners, on the other hand, Fila Signatures offer textured or "nubby cobble" soles, and Nike Air Zooms offer knobby barnacle-like soles. These bite into loose surfaces like dirt or grass, to lend more friction to runners who tear down a field at breakneck speed.

Companies like Reebok and Nike also brag about new advanced plastic compounds--like "Hexalite" and "Duralon"--used to toughen their soles. Reebok's Hexalite, for example, is a flexible plastic with honeycomb grids placed inside the soles. The grids are designed to spread out the force of impact and pamper your entire foot with extra cushioning.

At the end of the race, are the shoes really worth their steep price tags? According to most consumer magazine reports, kids find these snazzy sneakers don't turn them into Grant Hill. "Sneakers are engineered the same way as a car from the tires up, through the body of the car all the way to the seats," says Reebok's White. "How the car feels when you're in it is a big part of how everything works together." When it comes to spreading big bucks around for sneakers, you're in the driver's seat.