OK, let’s take a closer look at that stride
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.”
For example, gait analysis showed several of the girls, including Stephanie, tended to twist their upper bodies while running. (The computerized video measurement even showed the angle of the tilt.) Runners perform faster when their upper body is still. Moreover, twisting of the upper body can cause the thighs to rotate in too much. One common result of this abnormal rotation is a knock-kneed appearance and kneecap pain.
“We still had our share of injuries this season, but they weren’t as debilitating,” Casas says. “The runners were stronger.”
Video analysis can also include use of a pressure plate, a device that looks like a bathroom scale and gives information on how much pressure each part of the foot absorbs while running. For example, excessive pressure on the inside of the foot suggests an overly pronated foot, which can lead to strain on the connective tissues elsewhere in the foot. Ideally, pressure should be distributed more evenly throughout the foot.
As for digital analysis, it’s most useful in research settings, Ferber says. “It’s very technical, and the interpretation is relatively complicated.” Digital analysis can yield information that can be otherwise hard to detect. It can also show how the movements in a runner’s body are synchronized.
Davis says she prefers video gait analysis rather than the complicated charts and graphs produced in a digital analysis.
“When I sit down with the patient, they don’t understand the graphs,” she says. “But they can understand looking at themselves on tape. They can see it when I say, ‘See, your knee is coming in.’”
A digital gait analysis can cost up to $1,000 in a medical or sports clinic. The cost of video analysis varies widely. (It’s typically more in a clinic than in a retail store.) Prices can range from $45 in a store to several hundred dollars in a clinic. Visual footwear inspections are usually offered free or at a nominal cost. Health insurance will sometimes cover gait analysis performed in a medical setting if the purpose is to assess an injury.
Who should get one
Opinions vary on whether gait analysis is useful for everyone. Most biomechanics experts agree that almost everyone can benefit from a visual gait analysis to help them find the best running shoe. But some experts think more detailed gait analysis is best suited for competitive runners trying to gain a performance edge or for people who are trying to figure out the cause of a chronic injury.
Research shows that at least half of runners sustain an injury over the course of a year. Many are related to biomechanical flaws.
“The most common types of injuries we see in running are overuse injuries,” Dugan says. “There is something not ideal about your biomechanics.”
The most likely problems identified in gait analysis include an over-pronated foot that shifts weight to the inside and strains the connective tissues of the foot, ankle and knee. Over-pronation can lead to falling arches, bunions, hammer toes and heel pain and other foot injuries. (A pronated foot needs more arch support for stability.)
Another typical gait problem is supination, or under-pronation. Someone with supination has an insufficient inward roll of the foot and stress can be transferred to the knee or Achilles tendon. Plantar fasciitis can also result from supination. Runners with high arches and tight Achilles tendons tend to have supination. (The supinated foot usually needs a shoe with more cushion.)
But gait analysis can also show if one leg is shorter than the other, if the runner has a hip sway, excessive upper-body movement or other abnormal movement. An expert performing gait analysis will look at the entire body, or what Dugan calls the “biomechanic chain.”
“If you come to see me because your heel hurts, I need to look at your spine, your knees, your ankles, your toes,” she says.
The key to gait analysis, say experts, is to gain some useful information that will prevent injury. This can involve a simple change in footwear, use of orthotics, therapies to strengthen or add flexibility to muscles and changes to one’s mechanics or exercise patterns.
Malit at the Running Lab says, “My intervention is the shoe.” But if he spots complex mechanical or structural problems, such as the need for orthotics, he often refers customers to podiatrists, physical therapists or other medical experts.
A running coach or expert in biomechanics can perform gait analysis to recommend specific exercises or make changes in training regimens, Davis says. She uses biofeedback systems to teach runners how to change their mechanics.
For example, if a runner is landing too hard (a frequent cause of stress fractures), she can teach him or her to run more softly by having the runner perform on a treadmill linked to a device called an accelerometer. The runner can see the shock wave produced by his or her stride and can adjust, such as by shortening the stride or increasing the knee flexion, so that the shock wave is softened. Davis says many problems can be corrected -- and performance improved -- through biofeedback.
Consumers who undergo gait analysis should make sure they receive sound advice. Most experts suggest that gait analysis for injury diagnosis and treatment should be performed in a healthcare setting. Consumers who are getting the service in a store should inquire about the employee’s background and training.
“The value in gait analysis is in the person doing it, not the equipment,” Davis says. “If you’re getting a footwear recommendation, that’s not a big deal. But if it’s advice on mechanics, that’s something that requires training.”