Fitting Efficacy

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Fitting Efficacy

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August 2005 Biomechanics Magazine

By: CPT Lee Goss, MPT, OCS, ATC, R. Tortorelli, MPT, and

H. Saylor, RT, RDMS

Proper footwear has a role in preventing and treating running-related

lower extremity overuse injuries and low back pain. Running shoe

clinics can be an effective outreach tool to inform the public of

injury prevention strategies and maximize each runner's potential. A

greater awareness of the importance of selecting the right running

shoe and an increased understanding of the factors to be considered

in making that selection may help prevent many running injuries.

The numbers of people who routinely run for exercise and enter races

have been on the rise for several decades.1,2 With more people

running for their health,3 running injuries are a serious concern.

Between 30% and 70% of all runners will sustain an injury each year

that will sideline them for at least a week.4-10 Many of these

runners will not seek advice from a healthcare professional in a

clinic, but will ask other runners for advice.4,6 The most common

injuries seen in runners are iliotibial band syndrome (ITBS), stress

fractures, patellofemoral pain syndrome, Achilles tendinopathy,

plantar fasciitis, and tibial stress syndrome, or " shin

splints. " 2,7,9,11 High running miles (more than 30 or 40 miles per

week),1,2,4,10,11 a sudden increase in running miles,6,9,12-15 high

combined running and marching miles,16 and a previous history of

injury5 have all been suggested as reasons for an increased incidence

of overuse injuries.

Most experts agree that training errors, such as improper or

overtraining, increase the likelihood of overuse injuries; however

there is a discrepancy in the literature concerning foot morphology

and overuse injuries. Kaufman and Simkin7,17 found an increased

incidence of stress fractures in patients with pes planus and pes

cavus feet compared to those with normal feet. They found that

overpronation in planus feet led to a higher incidence of metatarsal

stress fractures and underpronation in the cavus feet led to tibial

and femoral stress fractures.7,17

However, Cowan and Giladi18,19 found a significant linear trend for

increasing risk of stress fractures with increased arch height, which

led them to coin the term " protective pes planus. " It is widely

accepted that the cavus foot does not adapt to the ground as well as

the other foot types. This inability to attenuate shock may lead to

higher stress fracture incidence or lateral ankle and leg injuries.18-

20 Simkin demonstrated that cushioned insoles in the boots of pes

cavus military recruits reduced femoral stress fracture incidence by

15.5% to 5.1%.17

In a small sample of 40 subjects, 20 found that high-arched

runners reported a greater incidence of ankle injuries, bony

injuries, and lateral lower extremity injuries. Low-arched runners

exhibited more knee, soft tissue, and medial lower extremity

injuries. He determined arch height by dividing the height to the

dorsum of the foot from the floor by the individual's truncated foot

length. He then theorized that arch height may affect the

distribution of injury in the lower extremity through its influence

on the mechanical coupling between the subtalar joint and the knee.

This coupling is related to the orientation of the subtalar joint

axis. A low arch with a relatively low angle of inclination at the

subtalar joint is thought to result in more eversion at the subtalar

joint and less tibial internal rotation.20 He believes the opposite

is true for the high arch. He admits, however, that it has been

difficult to establish a relationship between a single structural

deviation and a specific injury, as the etiology of injuries is

multifactorial in nature.

The lower extremity vertical shock wave resulting from ground

reaction forces is influenced by the position and orientation of

joint axes, neuromuscular activity, and strength.21 The effect of

running shoes on these factors is often underestimated. Shoes may

allow excessive movement or may reduce unwanted movement (like

pronation). Since significant differences can be found in the peak

pressure (approximately 20% body weight) and relative load patterns,

shifting weight medially or laterally in different shoe

constructions, the influence of footwear on the occurrence of overuse

injuries should be obvious.22

Efficacy of a clinic

These points support the theoretical efficacy of running shoe clinics

that address foot morphology and shoe design and are staffed with

knowledgeable professionals such as physical therapists or other

practitioners. Our running shoe clinics consist of an injury

questionnaire, a wet footprint test, a videotaped running analysis, a

flexibility and injury evaluation from a physical therapist, and

injury prevention education. Running shoe clinics are conducted

monthly at our local fitness center through a collaborative effort of

the physical therapy-sports medicine department, the wellness center,

and the fitness center. We advertise ahead of time and see 30 to 50

participants in an afternoon with a staff of five. Each participant-

they're scheduled every 10 minutes-cycles through all stations in

about 30 minutes. We also accept walk-ins. The clinics are free and

we do not endorse any particular shoe brand in our recommendations.

Our running shoe clinics have been very popular with our local

community. In nearly 300 six-week follow-up surveys, 98% have rated

the clinic " valuable " or " extremely valuable " and 90% have improved

their knowledge of injury prevention. In a study by the authors, more

than two-thirds of the runners who came to the clinic with pain rated

their pain decreased after six weeks.23 Figures 1 and 2 quantifiy

pain complaints of clinic participants by body part and foot type.

This popularity has spilled over into our clinical practice. By

assessing our patients' biomechanics and educating them in proper

footwear selection, we believe we have been more effective than if we

had just treated their symptoms alone. We recommend that all

healthcare professionals treating running injuries become proficient

in the evaluation and prescription of footwear in the hope of

preventing and reducing these types of injuries. Further research in

this area is certainly needed to determine the ultimate effectiveness

of different shoe types on preventing injuries in runners.

The primary purpose of a running shoe clinic is to match a runner's

foot (Figure 3) and running form with the appropriate shoe category:

stability, motion control, or cushion (Figure 4). Wearing the correct

shoe assists the runner in being more efficient and minimizes his or

her risk of injury. For example, a pes planus overpronator should use

a " motion control " shoe with characteristics in the design of the

shoe intended to complement the runner's form. Motion control shoes

are often built on board or combination lasts that are relatively

straight to match the planus foot. The medial side of the shoe

consists of a denser rubber or foam material often supplemented with

a plastic reinforcement to provide additional overpronation control.

The exact opposite is recommended for a cavus underpronator. Since

the cavus foot is rigid and does not adapt well to the ground, the

runner is using less foot to contact the ground. This increased force

per unit area on the plantar foot has been shown to attenuate shock

up the leg,18-20 so the shoe prescription must include additional

cushioning in the rearfoot and forefoot. " Cushioned " shoes are built

on a split, curved last that gives in the center lengthwise and is

matched to the shape of the cavus foot. There is often extra

cushioning, EVA or polyurethane, built into the midsole and some

designs include a denser foam or rubber on the lateral side to limit

excessive supination.

Neutral, efficient runners are generally prescribed a " stability "

shoe. Stability shoes have a combination of the characteristics

above. They can be made on combination, slip, or semi-curved lasts.

Neutral runners need little pronation or supination control, so the

shoes do not include this. Some models will include a small amount of

pronation control in the form of a denser foam medially without the

addition of a plastic buttress. It is widely accepted that between

50% and 70% of runners will fall in this category24 with 15% to 25%

in each of the special categories.

If the shoe fits

While arch index and footprint reliability measures are reported

consistently high,24-26 the validity of center-of-pressure measures

with rearfoot inversion and eversion has been questionable.27,28

Although widespread, use of footprint measures alone is not

considered a representative measure of the height of the medial

longitudinal arch26 and there is also a low correlation between the

static and dynamic arch index.7 For these reasons, we recommend using

a dynamic instrument gait assessment (ideally a slow-motion videotape

of the runner) and not the footprint alone. For instance, if a runner

has what appears to be a " neutral/normal " footprint but clearly

overpronates on a running video, we recommend giving them a " motion

control " running shoe prescription. This level of analysis can be

accomplished with a simple treadmill, a video camera, and a TV or

monitor for playback. No expensive software or equipment is required

for a basic assessment and runners appreciate the videotape feedback.

Following an ideal movement theory,21,29,30 abnormal or undesired

movements that place extra stress on the skeletal system may lead to

injuries. Any intervention that supports and facilitates " normal "

motion will decrease muscle activation and feel more comfortable.

Stabilizing joints and minimizing soft tissue vibration are two

strategies by which muscle activation may be minimized.21,30 Wearing

running shoes constructed with the intention of controlling motion,

providing additional cushioning, or increasing stability will alter

peak pressure and relative load patterns in the lower extremities.22

Therefore, it is not unreasonable to theorize that matching a runner

to a proper running shoe designed for him or her may reduce injuries

in the lower extremities and even reduce pressure on the spine.21,31

Thus, matching a runner's foot type and dynamic gait assessment to

the proper running shoe design may prevent and reduce running

injuries.

CPT Lee Goss, MPT, OCS, ATC, is chief of physical therapy-

sports medicine at Patch Health Clinic in Stuttgart, Germany, APO AE

09128. R. Tortorelli, MPT is staff physical therapist at the

same institution. H. Saylor, MS, RT, RDMS, is director of

the Stuttgart Wellness Center.

Acknowledgements

The authors would like to thank De Hoyos, Matt Hafertepen, Cory

Doubek, Carnegie, and the Patch Fitness Center staff for their

contributions to the Stuttgart Running Shoe Clinics. We would also

like to thank , Heidelberg Army Hospital Librarian, for

her assistance with the literature review.

The opinions and assertions contained herein are the private views of

the authors and are not to be construed as official or as reflecting

the views of the Departments of the Army or Defense.

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