The Effect of a Specialized Yoga Intervention on Characteristics of Functional Ankle Instability
Ankle sprain is the most common injury to active individuals, constituting between 15% of all injuries in high school and collegiate sports. Approximately 40% of individuals experiencing an acute ankle sprain go on to develop chronic ankle instability (CAI). CAI is characterized by perceived instability, episodes of the ankle giving way, and/or recurrent sprains of the ankle. There are two non-mutually exclusive types of CAI: mechanical instability (MI) and functional ankle instability (FAI). MI results from damage to musculoskeletal structures in the ankle joint complex causing pathological joint laxity or arthrokinematics restrictions. Functional ankle instability (FAI) is defined by the ankle giving way, in which a person experiences instability due to a near-sprain as a result of a benign or even an absent stimulus. Single leg balance training and interventions that improve ankle dorsiflexion have both been successful in reducing characteristics of FAI. Yoga is an exercise modality that incorporates poses emphasizing both single leg balance and ankle dorsiflexion. Additionally, yoga has been shown to be effective as a therapeutic intervention. One purpose of this study was to investigate the effect of a yoga intervention emphasizing single leg balance and ankle dorsiflexion on the perceived instability, ankle proprioception, and static and dynamic stability in participants with FAI. Chapter 2 summarizes the results of the effect of this specially designed yoga intervention on perceived instability and static stability. We found trends toward significant improvement in perceived instability as quantified using the Cumberland Ankle Instability Tool (CAIT) and some improved measures of static postural stability as quantified using time in balance and the number of foot lifts during single leg stance compared to a control yoga group in participants with FAI. Chapter 3 summarizes our findings of the effects on the yoga intervention on ankle proprioception. We found no improvement in ankle proprioception as quantified by active joint position sense error in five of the six measures in the yoga intervention group compared to the control yoga group. People with FAI are deficient in, among other things, dynamic postural stability. A common measure of dynamic postural stability in studies of participants with FAI is “time to stability” (TTS) following a dynamic, sports-related task such as jumping, cutting, or landing. TTS values show substantial variability related to changes in task characteristics, algorithms used in analysis, thresholds used to determine stability, sampling frequency, trial length, etc. In this dissertation project, we explored an alternative measure of dynamic postural stability in participants with FAI: the damping coefficient in a damped harmonic oscillator (DHO) model of center of mass acceleration during a single leg, lateral drop landing. Our results, summarized in Chapter 4, showed strong content validity of the DHO in modelling the center of mass acceleration, some significant construct validity findings correlating some other measures of stability with the damping coefficient in the DHO model, but poor trial to trial reliability. This dissertation project provides evidence that yoga emphasizing single leg balance and ankle dorsiflexion has the potential to be a safe, conservative treatment for people with FAI. It also shows that the DHO is an appropriate model for center of mass acceleration data during a single leg lateral drop landing, but the poor reliability of the damping coefficient parameter of the model prevents it from being a useful clinical measure for people with FAI. Future studies will address the effect of yoga interventions on the postural control of the hip in participants with FAI as well as exploring the conditions under which the reliability of the damping coefficient in the DHO model improves.
Physical therapy, Biomechanics, Ankle, Ankle instability, Ankle sprain, Modelling, Yoga
Networked Digital Library of Theses and Dissertations