Because it happens in the blink of an eye, a golf swing is often measured by the quality of the shot it produces. Unless, of course, you have the technology to slow it down.

"Our system is running at about 500 frames per second," says R. Barry Dale, PhD, PT, ATC, SCS, OCS, CSCS, discussing the eight-camera Vicon MX 3D optical motion analysis system in the Department of Physical Therapy at the University of Tennessee at Chattanooga (UTC), where he also serves as an assistant professor. "With a golf swing only lasting two seconds, this technology allows us to go to any single part of that swing and see what is going on, from one motion segment to another."

Dale evaluates golfers as part of research being done in association with a golf fitness program that evolved from a partnership between UTC and the Siskin Hospital for Physical Rehabilitation, Chattanooga, Tenn.

In addition to its efforts with golf biomechanics, research in the lab covers a range of topics, including spine biomechanics, clinical gait analysis, orthopedic surgery techniques, and footwear biomechanics, as well as orthotics, prosthetics, and orthopedic bracing.

The process of capturing 3D data is relatively straightforward. A series of markers are placed on the joints and other strategic locations of a patient's body, while cameras watch and record designated movement from multiple angles.

Reflected light coming from the markers is captured and processed by the system's software, producing 3D images that provide a wealth of information for clinicians and researchers alike.

"Once that data is in the system, you can then spin or manipulate the images in any way you want to, looking at them from whatever angle you choose," Dale says. The 3D rendering also can be played back, making it possible to view the same motion repeatedly, again from any number of angles. "With golfers, for example, if I want to look at the trunk versus the hips at the top of the back swing, I can. I will be able to see if they are too active with their trunk, because it will show you specifically if they are out of proportion."

Integrated force plates mean this technology works equally well—and, at UTC, is applied as often—as gait analysis. Dale's system allows him to compare individual segments to one another in terms of absolute motion.

"You can also track velocity, acceleration, and things of that nature. We have force plates that allow us to look at weight distribution, which is also vital from a gait analysis standpoint," he says. Details gathered from the force plates give insight into what is happening throughout the gait cycle. "Are they putting weight properly through the limb? Do they have the right propulsion? Are they pushing off correctly? It shows you basically where they are putting force into the ground, and all of that data integrates with the information you are getting from the optical system."

DIFFERENT, NOT BETTER

Despite the benefits inherent to being able to study images in three dimensions, this type of technology does not necessarily eliminate the need for 2D motion capture systems. Not only is it possible to obtain extremely useful data using 2D technology, but in some cases it's preferable, according to Dale.

"I would almost rather use a 2D golf swing when I am talking with a [patient], because they can relate to that image; they can see what's going on, and I can show them exactly what I'm talking about," he says. "With the 3D images, it's easy to overload the patient, so you want to try to keep it as simple as possible."

He does believe the 3D system provides his team with a more complete picture, as well as valuable qualitative—as compared to quantitative—data, but he doesn't believe that an elaborate motion analysis system like the one his lab employs would be the best fit for most clinicians.

With a price tag hovering around $150,000, the system is more complicated and demands more space than the average clinic is willing to sacrifice. UTC's situation is unique: the lab's focus is predominantly research. Partnerships with various clinics in the community mean a physician who is treating a patient with a complex problem or with multiple gait-related issues can refer that individual to UTC for evaluation and consultation.

For more traditional clinics, Dale believes a basic video analysis system is often enough to gather the necessary information.

"More often than not, 2D will correlate with what we see in the 3D images. The advantage of the 3D is you've got the velocity data within the different segments of the body," he says. This means that even if a swing may look good in 2D, the 3D images can verify if it's a technically correct swing in terms of sequencing and in terms of the body segments. "The 3D system gives us a complement to our qualitative data; it completes the picture for us."

PROS AND CONS

Typically, a 3D motion analysis system with force plates is considered to provide quantitative data, as opposed to qualitative, according to Dale, who explains that the latter accurately describes something and provides good information. With quantitative, it is possible to measure an amount of motion or force.

"That's why it's more of a research-type of application, because of the kind of data that we're getting," he says. "We're able to measure joint reaction forces of the lower extremities, especially during the gait cycle. And we can determine velocity and acceleration of the different limbs, as well as angular motion in degrees, angular velocity."

Even with the added detail, the system isn't perfect. The version in place at UTC does not readily allow for real-time motion analysis. After the subject has completed the movement and all postprocessing is complete, Dale will sometimes—particularly with the golfers—sit with the patient to review their likeness.

"We can pull the images up and look at velocity curves, for example, to show the person what they just did—but in terms of doing that while they are swinging and giving them real-time feedback, that is the unfortunate drawback to the system we have here," he says, noting that other systems, including some manufactured by Vicon, are beginning to include the real-time functionality. "What we can give them real time is their weight shifts on the force platforms, because you can see those arrows pretty well. But again, it is almost more qualitative."

LOOKING FORWARD

Thinking ahead to the next innovation, Dale is interested in learning more about the ability of the Optotrak Certus Motion Capture to collect EMG data. He also sees a lot of potential from another imaging modality: functional magnetic resonance imaging (fMRI).

fMRI is a relatively new procedure that uses a powerful magnetic field, radio waves, and a computer to measure the tiny metabolic changes taking place in an active part of the brain. It is becoming a proven diagnostic method for learning how a normal, diseased, or injured brain is working, as well as for assessing the potential risks of surgery or other invasive treatments of the brain.

"With a functional MRI, you're looking exactly at the anatomical structures themselves, and it's interesting, when you start thinking about being able to analyze someone in a sport-specific movement," he says, acknowledging the limitations of the fMRI systems currently on the market and the challenges associated with accomplishing this today. "I do think it will eventually make its way into clinical applications and even sport applications; some way, they'll figure out a way to do it so we could apply functional MRI to gait analysis or the types of research applications we're interested in."

Dana Hinesly is a contributing writer for Physical Therapy Products. For more information, contact .