Force sensors underneath the bindings of a snowboard are used to test torque and pressure on a snowboarders feet.
Force sensors underneath the bindings of a snowboard are used to test torque and pressure on a snowboarders feet.Photo by Andrew Tat
UW Ph.D. student Jeff Campbell is looking to make winter sports a little safer by combining two of his passions: skiing and physics.
Campbell began skiing when he was two years old. Since then, he has seen slopes from Salt Lake City to Mt. Hood. After recovering from a ski injury a few years ago, he directed his focus to the UW Applied Biomechanics Lab. Campbell is currently doing research that aims to make ski terrain parks safer.
According to Randy Ching, director of the Applied Biomechanics Lab, Campbell’s work is the first time there has been focus on optimizing safety in ski terrain design.
The technology and calculations used to design the size and scale of ski jumps use what are called ballistic equations, which calculate the path a thrown or launched projectile will take under the action of gravity while neglecting all other forces, such as friction from air resistance. To determine where the object will land, these equations treat the jumper as an object, much like a cannonball, and only account for the object’s initial velocity and the ramp’s angle.
Though widely used, Campbell explained that ballistic equations fail to account for the fluidity and dynamism of the human body, which also contribute to the body’s trajectory while jumping.
Campbell said the technology used to design most ski parks is rudimentary.
“It’s the best [method] that’s out there, but we believe that it’s not good enough,” Campbell said. “It can be made a lot better.”
In his hopes to derive more realistic mathematical equations for use in ski-jump design, Campbell decided to explore two main factors that current ballistic equations do not cover.
The first is how a rider’s center of mass shifts as the body continually moves during a ride. These movements can be subtle, but have a substantial impact on the success of a jump. For example, in his study, Campbell found a similarity in the way most jumpers’ knees flex as they go off a jump. This indicated that a particular knee orientation was a necessary component.
The second factor is the forces and torque — the tendency of a force to rotate an object around an axis — felt by riders while on a jump. Campbell explained that riders experience varying magnitudes of force as they move along a jump. For example, the deeper the dip in the snow before the jump, the greater the downward force felt by the rider. This force can lock a rider into unpredictable positions, which can in turn lead to unsuccessful jumps and possible injuries.
The data collection portion of Campbell’s research begins with the test subject putting on a Lycra suit coated with sensors. These suits are similar to ones that video-game animators often make their subjects wear to collect realistic recordings of human motions.
The subject then gets on a board equipped with small, light force sensors. Without interfering with the ride, these sensors measure all forces and torque experienced by the subject’s feet.
Researchers then analyze these force measurements. According to Campbell, the forces felt at one end of the body extend to the rest of it at varying magnitudes. This information corresponds to how components of a jump should be tailored, including the depth of the dip before the jump and the length or height of the landing.
For ski-park designers, this information can be used to create ramps and jumps that better fit the varying skills of their clientele. The findings also provide skiers and snowboarders an opportunity to learn the most efficient stance and body orientation when going off a jump.
“From an educational standpoint, this is valuable information,” Campbell said.
Ching said one of the priorities of the lab is to develop methods that prevent injuries in real life situations. He said Campbell’s work is both relevant and important to this goal.
Sheri Imsdahl, a doctoral student and Campbell’s colleague, said his situation is unique.
“What is so special about Jeff’s research is that he has such a connection to the ski and snowboard industry,” Imsdahl said. “It makes him really driven and puts him in a unique position to make a great contribution.”
By next spring or summer, Campbell hopes to be able to test these calculations on the “perfect jump.”
Reach contributing writer Christina Cho at email@example.com. Twitter @CCchews
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