Researchers develop hinged figure skate prevent to joint injuries

Apr 29 2004

Researchers at the University of Delaware have redesigned the traditional figure skate, with the goal of reducing the joint injuries that plague many competitive skaters.

The new skate, with a hinged boot that allows its wearers’ ankles to flex in order to cushion their jump landings, currently is being tested by a small group of skaters at the University and is scheduled to be available commercially this summer. The design allows skaters to point their toes during a jump, coming down toe-first with the rest of the foot hitting the ice more slowly, in a way that absorbs much of the impact of landing, according to Jim Richards, Distinguished Professor of Health, Nutrition and Exercise Sciences and director of the UD Biomechanics Laboratory.

“With the hinged design, you can land with your heel relatively high in the air, increasing the landing time and resulting in a lot less stress on the knees, hips and spine,” Richards said. “The current boot is so rigid that it’s like putting your ankle in a cast. It forces skaters to land flat-footed, which leads to the injuries you see so often—sometimes to the foot itself but primarily to the joints.”

The injury problem has grown in recent years as skaters are expected to do more and higher jumps, beginning at earlier ages, to be successful. Young competitors today commonly jump 50 or 75 times during a single practice session, each time landing with enough force to severely jolt their knees, hips and spine, Richards said. Such skaters as Tara Lipinski, who won the gold medal in the 1998 Olympics at age 15, and Naomi Nari Nam, who at age 13 in 1999 landed five triple jumps at the U.S. Nationals and was hailed as the sport’s next major star, have been sidelined with chronic hip injuries.

To illustrate his point about the mechanics of landing from a jump, Richards uses both scientific data and common sense. Jump off a low platform in your street shoes and try to land as softly as you can, he tells people in explaining the premise behind the hinged skate. When his listeners do so, they see that they have naturally landed on their toes to absorb the shock. Richards has corresponding graphs showing exact measurements of the force that occurs with a flat-footed landing compared with landing toe-first.

“If your toe hits the ground at the same time, or very close to the same time, as your heel, the total force of the impact spikes as much as eight to 10 times the person’s body weight, and for a very short period of time,” Richards said, pointing to a sharp peak on his graph. “If you can get your toe down long before the heel, we can decrease the impact by 20-30 percent. That’s a huge difference, and it’s critical to avoiding injury.”

Richards began developing the hinged boot design more than a decade ago, but the manufacturing company with which he was working at the time was sold and went out of the skating equipment business. The idea was revived recently when Jackson Ultima Skates, a Canadian manufacturer, became interested in a redesigned skate and contacted Richards and UD skating coach Ron Ludington.

Earlier this year, Jackson Ultima announced a partnership with the University and contracted with Richards to develop a prototype of the hinged, or articulated, boot. UD now holds a preliminary patent on the tongue design that, combined with the hinge at the back of the boot, allows a skater to move his or her foot up and down as if operating a gas pedal.

Key to the new design has been research conducted by Richards’ graduate assistant Dustin Bruening, who is completing his master’s degree this spring in health and exercise sciences and in the fall will begin work toward a doctorate in biomechanics and movement science. Bruening, a figure skater himself, spent last summer observing and recording research subjects repeatedly flexing their ankles while their feet were strapped to a hinged wooden platform. The data that resulted enabled him to precisely determine the best location for the skate’s hinge and for the rubber inset in the tongue.

“I had to figure out how to best match the ankle’s natural axis of motion,” Bruening said. “We came up with a placement that allows the skaters to flex their ankles [up and down] while forcing them to keep them straight [from side to side] so they can land with the proper control.” To avoid the problem of laces that might bite into the ankle through the flexible rubber part of the tongue, the new skate has laces only below the hinge and a buckle to hold the upper part of the boot in place.

Richards said skaters testing the prototypes take a couple of weeks to get used to the unusual ankle flexibility and then are comfortable with the new boot. Because appearance plays an important role in judging figure skating, athletes and coaches are expected to be wary of the redesign, he said, even though the U.S. Figure Skating Association has OK’d the hinged skate for competitions, as long as it is available to anyone who wants to use it.

“To Jackson Ultima’s credit, they know this isn’t an infinite market, so they don’t see the new design as a big money-maker,” Richards said. “But, they’re serious about trying to improve skating.”

“We had reached the conclusion that the needs of the figure skating community demanded a quantum leap in technology,” Malvin Loveridge, the company’s vice president of manufacturing, said. “Our relationship with the University of Delaware provides access to facilities that would be prohibitive for a private company to replicate. … The Delaware facility is amazing, and their testing capabilities are not available anywhere else in the world.”

Ludington, a World Hall of Fame and Olympic coach, some of whose skaters are testing the prototypes, said the new design “will allow us to address many of the equipment problems skaters have had to deal with in the past. We now have the ability to analyze new concepts and designs and gather real data that will help to improve performance and reduce the injuries associated with traditionally manufactured equipment.”

There is some early indication that the hinged skate might improve a skater’s ability to do certain jumps, Richards said, although that was not the impetus behind the redesign. “We never had in mind an increase in performance,” he said. “We wanted an increase in safety with no change in performance. If performance happens to improve, that’s a bonus.”

Kelsey Davidson, a junior majoring in health, nutrition and exercise sciences at UD, is one of the competitive skaters trying out the hinged boot. After a short period of adjusting her sense of balance to the new range of ankle movement, she said she is skating and jumping as she did before. Davidson has a personal reason for hoping the new design succeeds: Two years ago, she suffered a stress fracture to her lower spine and still experiences occasional pain when skating.

“Every other sport you can think of has added or improved protective gear for their athletes in recent years,” Richards said. “The exception is skating, where the kids are starting younger and doing more and more jumps, and they clearly need better protection from injury. You have skaters in their 20s who need knee and hip replacement surgery, and that just shouldn’t be happening.”