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Why Is Ankle Mobility Important Following Lateral Ankle Sprains?

BYU Human Performance Research Center Biomechanics Laboratory
Provo, Utah
MedicineNeuroscienceGrant: Exercise Research
$14
Raised
1%
Ended on 1/02/17
Campaign Ended
  • $14
    pledged
  • 1%
    funded
  • Finished
    on 1/02/17

About This Project

Some people have more risk of ankle sprains than others. Restricted ankle mobility makes ankle injury 5 times more likely. Each individual with a history of ankle injury reveals a different level of deficits and severity following injury. Considering various levels of deficits, some people likely have normal mobility similar to healthy people, which begs the question as to whether unstable ankles with normal mobility would reveal less risk for injury in a neuromechanical view.

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What is the context of this research?

Ankle sprains occur at a high rate (one of every 10,000 people) daily in the general public. After a single ankle sprain, up to 80% of people suffer repeated ankle sprains, which often develop into chronic ankle instability (CAI).

CAI is characterized by increased ligament laxity, impaired balance, impaired proprioception, muscle weakness, delayed sensory response, and/or restricted ankle mobility.

Tension force during injury results in a positional fault of the talus, which prevents the ankle from reaching its stable position. This restricted mobility leads to a shorter distance and faster angular rotation to reach an injury-prone position which results in a deficient time to develop protective tension from counteracting muscles.

What is the significance of this project?

First, we will use a novel error-driven experimental model that places the foot into an ankle sprain position during walking using a walkway platform. This experimental model will replicate lateral ankle sprain mechanisms (not causing injury) with a trap door that falls into 30 deg inversion during walking.

Second, as 75% of all reported ankle sprains occur during landing and side-cutting, we have developed a dynamic task that mimics typical ankle injury mechanisms.

Third, due to variations in patient’s physical status and levels of deficits in a CAI population, it is necessary to make subgroups of CAI based on ankle mobility.

What are the goals of the project?

This study aims to examine the effects of ankle mobility on reactive responses to repetitive inversion stress. We will examine whether CAI patients with normal mobility can demonstrate better neuromechanics during landing.

We hypothesize that CAI patients with restricted mobility would show a higher susceptibility to ankle sprains such as reduced muscle activation, unstable joint positions when compared to both CAI patients with normal ankle mobility and matched healthy controls.

If this hypothesis is correct, it would change the current treatment paradigm wherein clinicians treat a “homogenous” injured population the same. Rather, the ankle instability patient should be treated differently based on ankle mobility (restricted vs. normal).

Budget

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Monetary compensation will be awarded to each subject at the completion of data collection in the amount of $20. Each subject will report to the BYU biomechanics laboratory for a single visit session, which will take about 90 minutes.

A total of 90 recreationally active people (30 CAI patients with restricted ankle mobility, 30 CAI patients with normal ankle mobility and 30 matched healthy controls) will be recruited from a community-based population aged 18-50 years.

Endorsed by

This is a well developed project that should help identify the significance of limited ankle motion on movement mechanics. Ankle instability is a multifactorial problem, and limited mobility may play a larger role in muscle function, dynamic joint stability, and altered movement. This project is well designed, and it has the potential to provide essential information about the role of limited ankle motion in perpetuating ankle instability.

Meet the Team

S. Jun Son
S. Jun Son
Graduate Student

Affiliates

Brigham Young University
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S. Jun Son

https://www.researchgate.net/p...

Hi, I'm Jun. I am a doctoral student in the Department of Exercise Sciences, with an emphasis in lower extremity joint injury and rehabilitation at Brigham Young University. I earned my BS and MS in Athletic Training from The University of Texas at Austin and Brigham Young University, respectively.

My advisor, J. Ty Hopkins, PhD, and I have been working on several chronic ankle instability research studies over the past 15 and 5 years, respectively. Our research aims to develop a better understanding of mechanisms of chronic ankle instability and to define a more effective treatment intervention, and thereby minimizing the long-term consequences of ankle injury.

Lab Notes

Nothing posted yet.

Additional Information

CAI research has shown several deficits including increased ligament laxity, impaired balance, impaired proprioception, muscle weakness, delayed sensory response, and/or restricted ankle mobility. Restricted ankle dorsiflexion mobility is of particular interest in this project. Tension forces during lateral ankle sprains result in an anterior positional fault of the talus, which prevents an ankle joint (e.g., tibiotalar or talocrural) from reaching its rigid, stable, close-packed position and thereby restricting full ankle dorsiflexion mobility. This restricted ankle mobility leads to greater risk of ankle reinjury due to a shorter distance and faster angular rotation to reach a maximal inverted or supinated position of the foot which ultimately results in a deficient time to develop protective tension from counteracting muscles (e.g., peroneus longus, peroneus brevis and tibialis anterior). As such, restricted ankle dorsiflexion mobility would place the foot in a more loose-packed, injury-prone position (e.g., plantarflexion and inversion) during movement.

There are three unique features in this project: (1) a new group comparison, (2) a landing task and (3) an error-driven experimental model. First, previous ankle research has compared CAI patients to healthy controls to identify a mechanism of repetitive ankle sprains. However, this common comparison does not consider between-patient variability in this injured population. Since each CAI patient would have a different level of deficits and/or severity after ankle injury, it is necessary to consider subgroups of CAI based on each patient’s physical status. This speculation led us to consider the idea that some CAI patients likely do not have restricted ankle mobility similar to a healthy population. For a group assignment in a CAI population, we will use 45 degrees of ankle dorsiflexion during a weight-bearing lung test as a cut-off score, which is average dorsiflexion angle from healthy individuals (n=1093).

Second, previous work has used various landing tasks (e.g., drop jump, stop jump, vertical jump, or lateral jump) to examine risk factors for ankle injury, but these landing tasks may be oversimplified and uniplanar without directional changes compared to sports activities. This provides limited generalization to an active CAI population. As 75% of all reported ankle sprains occur during landing and side-cutting, we have developed a more dynamic, multiplanar, sport-specific task which contains a component of maximal vertical forward jump, a single-leg sudden deceleration during a high impact landing, and an immediate side-cutting acceleration. Our landing task simulates movement that often occurs during sports activities and further mimics about 75% of typical ankle sprain mechanisms.

Third, in order to examine feedback (reactive) and feedforward (proactive) controls during landing, we will use a novel error-driven experimental model that places the foot into an inverted position during walking using a walkway platform. This experimental model will replicate lateral ankle sprain mechanisms while not causing injury with a trap door that falls into 30 deg inversion during walking. As a normal self-protective mechanism, when the foot is in a vulnerable position to lateral ankle sprains, the body would increase muscle activation and place the foot into more stable positions (e.g., eversion and dorsiflexion) in a manner that protects the ankle against injury. However, given a shorter distance and faster angular rotation to reach a maximal inverted or supinated position of the foot due to restricted ankle mobility, we believe the sensitivity of self-protective mechanism would be worse in CAI patients with restricted ankle mobility compared to both CAI patients with normal ankle mobility and matched healthy controls.


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