STEPHANIE Felix didn't realize running could be so complicated.
The high school junior took up the sport a few years ago and quickly emerged as a top distance runner at La Mirada High School. But then her coach had team members' gaits assessed.
The analysis, in which Stephanie was videotaped while running on a treadmill, showed a litany of problems. She shifted her weight to the inner foot, which could lead to ankle and foot injuries. Her arms swung too much, which could cause misalignment in her lower body. And she had a heel strike, meaning the heel of her foot hit the surface first, placing more stress on the heel and slowing her down.
"I was really surprised by what I saw," says Stephanie, 16. "I learned a lot about my form that I didn't know -- that it matters how your heel hits, where your arms are. When you have good form, you're a better runner."
And perhaps a less injured one too.
Long used in medical settings to help people with movement disorders, such as cerebral palsy, learn to move more efficiently and with more stability, gait analysis is increasingly offered in running and footwear stores.
Casual joggers and walkers are using the analysis to find comfortable -- and productive -- footwear, to prevent injury and assess chronic injuries or soreness.
In general, gait analysis is the study of foot motion during normal running and walking. The process evaluates the foot's anatomical structure, muscle flexibility and strength -- assessing how those factors influence the way a person runs or walks.
Weak or inflexible muscles, if stressed by a lot of running over time, can lead to injury. And even a simple movement such as an excessive arm swing can make a difference in the performance of a competitive runner, adding a precious second or two to running times.
"It shows you things from a biomechanical standpoint: What are you doing when you run? What small improvements can you make?" says Reed Ferber, director of the running injury clinic at the University of Calgary in Alberta, Canada. "But it also suggests things on the clinical side, such as where someone is inflexible or weak in a specific muscle."
Several forces have merged to popularize the service in recent years, such as more user-friendly video and computer technology and athletic footwear that requires more thoughtful shoe fittings. At the Running Lab in Orange, owner Earl Malit displays shoes by their specific function -- extra support, more cushion, added stability -- not by brand or price. The store also features a gait analysis lab with a treadmill, video cameras and a computer to receive the information and analyze it. "We don't just look at the foot," Malit says. "The whole point of gait analysis is to understand why you do what you do."
Watching your step
Gait analysis can be simple or highly sophisticated. Footwear stores often offer the simplest method -- a visual inspection of the foot and shoe. More specialized stores and many physical therapy and sports clinics offer video gait analysis, in which a person is taped while running on a treadmill and their movements are studied. An even more sophisticated method includes a digital analysis using video- and motion-analysis computer software that can produce two-dimensional or three-dimensional images.
"There are all sorts of gradations," says Dr. Sheila Dugan, an assistant professor of rehabilitation medicine at Rush University Medical Center in Chicago. "The different types of gait analysis assessments will give you different information."
During a visual inspection, store employees typically examine patterns of wear on the customer's old running shoes. "Shoes tell a history if they're well-worn," says Irene Davis, a professor of physical therapy at the University of Delaware. For example, a worn heel can suggest a heel strike, in which the heel of the foot strikes first instead of allowing a larger surface of the foot to absorb the shock. Runners who land hard can develop stress fractures more easily.
The customer is also asked to walk across the store so that problems with knock-knees, splayed feet, pigeon toes or falling arches can be identified. The foot should also be measured, Malit says, including length, width and arch length.
In video analysis, a customer is taped from various angles. The tape is then played back frame by frame to identify specific movements not visible to the human eye.
Stephanie underwent gait analysis because her coach recommended it. Ralph Casas shepherded his La Mirada cross-country team to the Running Lab last August and says he'll take his team back every year.
"The kids thought it was neat," he says. "And it was helpful to us as coaches because we could then tailor workouts and strengthening exercises that would target what they needed to do."