THE PUMP -- it's not a rap song or a dance -- is the latest in shoes from Reebok, a high-concept, high-priced high top that literally puts the squeeze on an athlete's feet. "The ultimate fit and an amazing degree of ankle support," say the ads.
Support, physical support, is the name of this game. High-top shoes were originally designed with our inherently weak and wobbly ankles in mind. In theory, the thick leather cuff of a modern high top supports the ankle and prevents sprains.
Reebok's new shoes take this notion a step further by incorporating a plastic bladder that inflates with a miniature hand pump built right into the tongue -- "to protect your ankles."
Better ankle stability is surely a great goal to shoot for. Sprained ankles are probably active people's most common injury.
When you jog gently off a curb and "twist" your ankle, you tear a small number of fibers in one of the tough ligaments on the outside of the ankle. That's a mild sprain.
When a tennis player lunges out over a poorly planted foot, more of those ligaments' fibers tear -- and that's a moderate sprain.
When a basketball player jumps and lands on another player's foot, driving an ankle violently to the court and tearing most or all of the fibers, that's a severe sprain.
Ankle sprains account for 20 percent of the injuries seen in busy sports medicine clinics.
"We really don't know how many people sprain their ankles each year, because most recreational athletes treat their sprains themselves," says Thomas Miller, executive director of the Sports Medicine Clinics Association. The nation's busiest clinics each see scores of ankle sprains a day, which comes to millions a year.
In that light, there's a fine logic to the new puff-'em-up shoes -- or to anything that might stiffen the ankle. Wrapping ankles tightly with wide athletic tape is a tried-and-true method.
But studies show that tape tends to loosen with activity, so some sports doctors now suggest lace-up cloth braces that can be tightened during a timeout. Others also recommend a gizmo called the Air-Stirrup, which consists of two sets of inflatable bladders laced together so they run up both sides of the ankle.
And that, in effect, is what the Reebok Pump is, an ordinary leather high top with a set of miniature quilted air mattresses built into the sides and tongue.
Critics say Reebok's new high-top shoes may not do anything more than comfortably coddle the ankle and foot.
Convincing research is hard to come by in this field. Studies point in opposite directions. Experts contradict one another. Advertisers post exaggerated claims for their products without legitimate research to back them up.
Still, evidence suggests that something snug around the ankle does seem to help. For instance, a study of 2,500 college intramural basketball players showed that players with a history of ankle sprains who wore high tops on the court suffered half as many ankle injuries as those who played in low tops.
The sum of the research to date suggests that high tops are actually more likely to limit the severity of a sprain that to prevent it altogether.
Yet strangely, the shoes' physical support may have little to do with the lower rate of injury.
Consider a Swiss study of handball players who had special high-top shoes designed for them. The new shoes did lead to few ankle sprains, but slow-motion photography proved that the high tops did nothing to improve the side-to-side stability of the players ankles. What exactly is going on here?
The mere illusion of support apparently does the trick. Wearing a high-top shoe seems to help the body sense more readily how far the joint is flexing. As your ankle begins to roll over, the feeling of flesh and bones pressing out against the shoe sends a subconscious message to your brain to do something, quick.
This early warning may help reduce the sprain's severity by allowing you to right your foot as much as possible just before it hits the ground, according to biomechanist Edward C. Frederick, president of Exeter Research in Brentwood, N.H.
To get a sense of what happens, sit in a chair, lock your hands beneath one thigh, then raise the leg and dangle your foot in the air. Point your toes down, and your ankle will turn slightly toward the ground. Now turn the outer edge of your ankle farther toward the floor, and you'll feel the muscles above the ankle tighten up.
A high-top shoe, with the additional pressure of a high collar, helps you feel these muscles contract as the ankle starts to roll over.
It may seem that high tops provide added support, but the shoe itself isn't controlling the ankle joint. You are, by altering your foot position with the help of early nerve signals from muscle to brain.
"Perception is bigger than reality. There's no evidence that a high-top shoe gives your more support," says Tom Brunick, director of the Athletic Footwear Test Center at North Central College in Illinois.
For that matter, taping your ankle, bracing it or even wearing a stretchy elastic band also stimulates the signals that help protect the ankle from severe sprains. Inflatable shoes? Well, there's no evidence that they're an exception.
What's more, the same principle applies to hiking shoes, says James Rippe, director of the exercise physiology and nutrition lab at the University of Massachusetts Medical School. Walking a slow speed over rough terrain, you have even more of a chance for the ankle-to-brain feedback to kick in.
He says that the new sneaker-weight, high-top hiking shoes offer just as much protection from sprains as do traditional, heavy combat or hunting-style boots.