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Taking a Load Off

Researcher’s unweighting device gives
patients a new, lighter road to recovery

UM researcher and inventor Ryan Mizner guides Anna Johnson, a UM freshman in athletic training and veteran of three knee surgeries, in the use of his BRIDGE unweighting system.Only a dozen men ever have experienced the one-sixth gravity of the moon as they walked — more of a hop-skip, really — across the lunar surface and into history. After just a few days in reduced gravity, they came back from their mission literally weak in the knees. But for patients who find themselves in UM Assistant Professor Ryan Mizner’s low-gravity environment, the goal isn’t to slip the “surly bonds of Earth” and walk amongst the stars. They simply want to walk again.

In a physical therapy lab brimming with high-tech equipment, Mizner has built a cutting-edge device to provide patients — ranging from those recovering from knee surgeries to those suffering severe brain injuries — with a path to recovery that’s surprising in both its simplicity and its efficacy. A series of cords and pulleys, carefully calibrated to provide varying degrees of resistance, eventually wend their way to an unassuming-looking harness, which, once attached to some custom-built compression shorts, can lighten a patient up to 30 percent of their body weight.

The Bodyweight Reduction Instrument to Deliver Graded Exercise (BRIDGE) offers consistent vertical force no matter what the movement. Or, as Mizner says: “What we’re doing here is reducing gravity.”

Unweighting devices, whether mechanical, pneumatic or otherwise, aren’t new. But while other methods of lightening a patient’s load are confined to small movements of a patient’s core like walking or running on a treadmill, Mizner’s device is dynamic in all directions, allowing physical therapists to have patients make lateral and vertical movements that closely mimic the moves they’ll make outside the lab’s walls.

“A patient in a fully weighted environment might only be able to make a maximum of 120 repetitions of a jump motion, but when you’re able to severely reduce the loads their body is experiencing, you can increase that number and give therapists the opportunity to work with a patient for 350 or 400 repetitions,” Mizner says. “And with unrestricted motion those reps can be sport-specific movements like vertical leaps, basketball cutting or volleyball blocks.”
Mizner also theorized that being able to make more dynamic movements more times could have value beyond the return of muscle memory and strength.

Mizner adjusts the elastic tubes that create the BRIDGE unweighting.As a former collegiate athlete himself — he threw hammer and javelin at Montana State University before heading to the East Coast to earn his master’s of physical therapy and doctorate in biomechanics and movement science at the University of Delaware — Mizner saw firsthand how even when athletes have a complete physical recovery from an injury, they still have psychological hurdles to overcome. If jumping, cutting and other high-load movements are what caused an ACL to tear, it can be hard to trust those motions again and return to pre-injury levels of performance.

“In traditional jump retraining, patients will often self-limit loads borne by their repaired knee due to insecurities. Concurrently, clinicians will often limit their practice of those movements due to the intense joint loads during practice,” he says. “A novel approach to deliver graded exposure is needed. If we can cut the load and start increasing repetitions, then patients can learn to trust the joint stability.”

That idea earned Mizner a $40,000 grant from the Foundation for Physical Therapy last year to conduct a double-blind study for 30 patients recovering from ACL reconstruction to test their response to the BRIDGE-based therapy versus the current best practices. Mizner says he anticipates seeing improved rates of people participating in sports with lower risk for secondary injury after a knee surgery. The idea goes beyond ACL reconstruction to patients with other issues, such as chronic pain, who can benefit from carefully managed graded exposure to loading.

The potential benefits of Mizner’s BRIDGE device are such that there’s already talk of how the collection of half a dozen 200-foot elastic cords and repurposed climbing and mountain rescue pulleys can be packaged for use outside of his UM lab and used by physical therapists in their own practices.

That task falls in part to UM Director of Technology Transfer Joe Fanguy, who works with University researchers to help turn their discoveries into marketable, commercialized products and services.

“The University is in the business of research, not necessarily commercializing a product, and so over the past several years we’ve really tried to raise awareness of this option and encourage people to explore it,” Fanguy says. “Ryan has put a ton of effort into prototyping his system, and as a result we have a much clearer picture about the commercialization potential.”

Fanguy says making the transition from laboratory to a viable business is never easy and requires not only a great idea, but also a mix of individuals with technical and business acumen to form a team that’s up to that task of making and bringing a product to market.

For Mizner, he envisions further refining the prototype to take up a smaller footprint and even structure the system in a way that it could be mounted out of sight above drop-ceiling panels to avoid taking up valuable real estate on a clinic floor. It’s a far cry from the early models, which were strung up on progressively taller wooden A-frames to test the concept before the current-generation hardware was bolted to the floor and ceiling of the Skaggs Building basement.

And whether BRIDGE evolves into a manufactured product that can be packaged for any forward-thinking physical therapy clinic to purchase and install, or becomes the basis for a service-based offering that could be a destination center for patients from around the region, both Mizner and Fanguy think the future is bright.

“Commercializing these ideas is about more than making money, it’s about the vision of providing job opportunities for the very students these professors are working with,” Fanguy says. “I think there’s enough strength with Ryan’s invention for us to consider the potential for great impacts in western Montana and beyond.”

— By Alex Strickland