October 2015

Shoes, orthoses improve muscle activation onset in unstable ankles

Ankle-FigureLER

In the KU Leuven study, participants shifted from a double-leg stance to a single-leg stance. (Photo courtesy of Bart Dingenen, PhD, PT)

Custom insoles have greatest effect

By John C. Hayes

A study of patients with chronic ankle instability (CAI) suggests the onset of knee and ankle muscle activity occurs significantly earlier when shoes and orthoses are worn than when the patients are barefoot.

If borne out in further research, the report in the Journal of Athletic Training may provide validation for the idea that patterns of muscular activation can be improved by shoes and orthoses and provide patients with CAI added protection against an ankle “giving way” during sports and other activities.

The study conducted by Belgian researchers included data from 15 students at the Faculty of Kinesiology and Rehabilitation Sciences at KU Leuven in Belgium, all of whom had at least two lateral ankle sprains and symptoms of CAI and who had worn foot orthoses for at least six weeks. They were young (21.8 years + 3 years) and active, but were not athletes, said lead researcher Bart Dingenen, PhD, PT, a sports physiotherapist in KU Leuven’s Musculoskeletal Rehabilitation Research Group.

Investigators collected data via surface electromyography and a force plate as the participants shifted from a double-leg stance to a single-leg stance. They repeated the process under four conditions: barefoot, shoes only, shoes with prefabricated “standard” foot orthoses, and shoes with each patient’s custom foot orthoses.

The observed improvements in muscle activation onset associated with shoes and foot orthoses extended from the ankle through the knee.

Each participant received a pair of standardized neutral running shoes and a pair of prefabricated ethylene vinyl acetate foot orthoses. The height of the medial arch support of the standard foot orthoses was based on the correction of half the navicular drop excursion; rearfoot posting was added as necessary.

Muscle activation onset occurred later in the barefoot condition than when the participants wore shoes, either with or without orthoses. Shoes with custom orthoses outperformed shoes alone or shoes with standard orthoses. The study also found that the improvements in muscle activation times extended from the ankle through the knee.

Muscle activation timing is a significant issue in CAI. An ankle sprain can occur within 80 to 100 milliseconds after ground contact, Dingenen said. An electromechanical delay in muscle activation limits the muscles’ ability to counter the ankle’s tendency to roll.

“Anticipatory muscle activation is essential to protect against ankle sprains,” he said. “These types of experiments can improve our understanding of neuromuscular control during functional tasks and its difference in contributing to outcomes. “

Dingenen hypothesized that, when patients wore the custom foot orthoses they were used to, the distal sensory information is more reliable for the central nervous system, leading to earlier motor output compared with the other conditions.

Previous research, including a 2001 study in Clinical Biomechanics and a 2008 study in Foot & Ankle Specialist, has suggested that shoes and orthoses may improve proprioceptive input to the central nervous system by increasing contact area between the foot and the supporting surface.

But it also may be that shoes and orthoses, by separating the foot from the ground, actually decrease proprioceptive input, said Gregory M. Gutierrez, PhD, assistant professor of Physical Therapy & Rehabilitation Sciences at the University of South Florida in Tampa. This may make muscles activate earlier, becoming primed for a destabilizing event when sensation is poor; for example, when one is navigating a snowy or icy street.

“We cannot directly measure proprioception, we can only measure its ramifications, and in this case, the results would be the same,” said Gutierrez, a biomechanist who has done activation studies and whose primary interest is CAI.

“The study is another building block in our understanding of how persons with ankle instability interface with the world and how we can improve outcomes for them,” he said.

For Dingenen, the path ahead involves longitudinal studies to see how activation onset changes over time. He would also like to look at specific pathological populations and perhaps obtain prospective activation onset data from noninjured persons to see which are more likely to get ankle and knee injuries.

As the field progresses, one challenge will be determining how to obtain dynamic data during tasks that more closely resemble activities associated with ankle sprain, something that is difficult with current technology, Gutierrez said.

“People don’t sprain their ankle when they are going from a double-limb to a single-limb stance. They sprain their ankle when they are walking, running, jumping, cutting, or other dynamic activities,” he said.

John C. Hayes is a freelance writer based in San Francisco.

Sources:

Dingenen B, Peeraer L, Deschamps K, et al. Muscle-activation onset times with shoes and foot orthoses in participants with chronic ankle instability. J Athl Train 2015;50(7):688-696.

Nurse MA, Nigg BM. The effect of changes in foot sensation on plantar pressure and muscle activity. Clin Biomech 2001;16(9):719–727.

Sesma AR, Mattacola CG, Uhl TL, et al. Effect of foot orthotics on single- and double-limb dynamic balance tasks in patients with chronic ankle instability. Foot Ankle Spec 2008;1(6):330–337.

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