Researchers examine influence of foot orthoses on running gait

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Biomechanics Magazine August 2006

Researchers examine influence of foot orthoses on running gait

By: Jordana Bieze

http://biomech.com/showArticle.jhtml?articleID=192700631

Gait analysis findings presented at the annual meeting of the

American College of Sports Medicine continue to illustrate the ways

in which foot orthoses alter running mechanics. But the extent to

which those alterations are beneficial or potentially injurious is

not yet entirely clear, and may depend on an individual runner's

anatomical and biomechanical characteristics.

Research from the University of British Columbia suggests that the

effectiveness of moderately posted foot orthoses in runners may be

limited by the type of running shoe in which the orthoses are worn.

The investigators used goniometers to measure rearfoot motion in the

frontal plane and knee motion in the sagittal plane as 15 female

runners ran on a treadmill under two orthotic conditions and two shoe

conditions. When no orthoses were worn, the researchers found more

intralimb coordination variability with a motion control shoe than

with a neutral shoe. However, when the runners wore orthoses with 3

degrees of rearfoot posting, more intralimb coordination variability

was associated with the neutral shoe.

Given that in the June 1999 issue of Clinical Biomechanics,

researchers from the University of Massachusetts at Amherst reported

less variability of intralimb coordination in injured runners than in

healthy runners, the UBC findings suggest that wearing a moderately

posted orthosis with a motion control shoe could put a runner at risk

of injury.

" The ideal combination for this group is a neutral shoe with their

orthoses, " said Baker, MSc, a former graduate student in

sports medicine at UBC, who presented her group's results at the ACSM

meeting. " However, the less posting you use, the more ambiguous the

effect becomes. With this group it's possible they could have gone

either way with a shoe or an orthosis. "

Researchers from the University of Kansas also found that orthoses

were associated with increased variability, but reached a different

conclusion about the implications of their findings. In 30 runners

identified as being excessive pronators, they found that the use of

soft prefabricated orthoses significantly increased variability for

ankle range of motion in the transverse plane, knee range of motion

in the transverse and frontal planes, and knee peak angular velocity

in the sagittal plane.

The increased kinematic variability seen with orthosis wear suggests

the orthoses may not be having their desired effect, said

Brethauer, ATC, a graduate student in biomechanics at the university,

who presented the group's findings at the ACSM meeting.

" Theoretically, the idea for excessive pronators is that you want to

control motion. So with orthoses we would expect to see less

variability, " Brethauer said.

Two other studies presented at the ACSM meeting suggested benefits of

custom foot orthoses in runners.

A University of North Carolina study found that custom semirigid

orthoses can help counteract the effects of fatigue that may increase

a runner's risk of plantar fasciitis. In six runners, the devices not

only helped maintain arch height but also decreased plantar fascia

tension during midstance phase before and after local muscular

fatigue was induced.

In a study of 18 high-arched and 19 low-arched runners, researchers

from the University of Delaware determined that a custom foot

orthosis produced more rearfoot control than a semicustom orthosis

but that the effectiveness of either type of orthosis was not related

to arch height. They did find that high-arched runners were less

comfortable in the custom orthoses than the semicustom orthoses while

walking, but not while running. The low-arched runners were equally

comfortable in the two devices at either pace.