Hard-Hitting Research

Professor Dennis K. Lieu with martial arts headgear strike-testing apparatus. Photo credit: Dennis K. Lieu. Professor Dennis K. Lieu with martial arts headgear strike-testing apparatus. (Photo by Dennis K. Lieu.)For 10 years, mechanical engineering professor Dennis Lieu moonlighted as an instructor in the martial art of taekwondo, which emphasizes full-contact kicks and punches to the head and body. During that time, he saw the sport become more safety conscious, and out of his own interest and concern, began testing commercial martial arts headgear that had become standard and required for competitions. His results were startling: many of the helmets failed his tests and, he concluded, would not prevent injuries.

“Look inside a cycling, football or motor sports helmet, and they all have labels saying that they pass the relevant ASTM safety standard,” Lieu explains, “But look inside martial arts headgear, and you just see a label saying ‘Use at your own risk.’”

After taekwondo sparring became an official Olympic event in 2000, Lieu put his research into full gear, setting up an area in his lab where he subjected test helmets to calibrated pummeling from a pneumatic arm. He outfitted each helmet with acceleration sensors that fed into a laptop, which analyzed the impacts for brain-damaging, neck-snapping potential. From these tests he created the first technical standard for martial arts protective headgear, the ASTM F2397.

Although approved by the ASTM, the American Society for Testing and Materials, in 2004, Lieu’s ASTM F2397 is not yet required competition gear. He thinks it is just a matter of time before it is a requirement. “It’s a slow process, but eventually I expect it to be driven by the insurance companies. They’ll start asking, ‘Did the equipment meet the safety standard and, if not, why not?’”

Lieu is now working on a martial arts chest-guard standard, which presents a different problem. Heads are injured when rapid acceleration bounces the brain inside the skull; they are best protected by thick materials that absorb energy and decrease the acceleration. Torsos, in contrast, are injured when concentrated pressure crushes ribs or soft tissue. Cushioning may protect against this, and existing chest-guard standards, for baseball, for example, prescribe this approach. But a better solution (especially for sports) is a thin, hard shell that disperses the energy over a larger area, converting a gut-penetrating blow into a broad shove.

To test body armor designs with his pneumatic kicker, Lieu and his students developed a torso made of silicone, instrumented inside with pressure sensors. The sensors are embedded in fluid bubbles that enable them to detect strikes over a wider area and eliminate the hot-spot effect directly over the sensor sites.

The instrumented torso also works well for testing non-lethal projectiles, which Lieu became interested in after the controversial shooting in 1997 of Kuanchung Kao by Sonoma police, who mistook him for a martial arts expert and a threat. “That had a big impact on me,” Lieu recalls, “and I thought that, if the police had had another option, his life might not have been lost.”

Lieu looked into rubber bullets, bean-bag disks and other so-called non-lethal projectiles; he discovered that one percent of the shots actually do kill people, while many more cause serious injuries. Some of Lieu’s undergraduate students began making alternative projectiles for the standard 37-mm projectile launchers used for riot control, then tested them in the ballistics lab in the basement of Etcheverry Hall.

Soon they found the magic bullet that might knock someone down without injuring them: a sphere of soft silicone that pancakes on impact, but delivers almost all of its energy into its target. The balls perform well in any weather and can even be fired at higher than standard velocities. Lieu hasn’t yet looked into commercializing the projectiles, but expects that they would stand up better than now-standard non-lethal munitions in lawsuits against law enforcement.

Lieu also conducts research on electromechanics, designing smoother-running motors and actuators. But it’s his work with martial arts and projectiles that attracts the most attention.

“The biomechanics research is technically much simpler than my other research,” Lieu explains. “It makes more sense to people. Anyone who’s ever been hit can relate to it.”