Assessing Concussion Recovery With Dynamic Stability Methodologies

The overarching purpose of this dissertation was to investigate methods and measures of dynamic stability with the final application being assessment within a concussed population. Of the three studies presented, the focus of the first two studies was on development of a new measure of dynamic postural stability, comparing it to traditional methods, and determining how it performed relative to traditional methods. In the first study, participants performed a forward hop while kinematic and kinetic data were collected. Comparison of the kinetic estimation of the center of mass to the kinematic estimation showed moderate to strong agreement. This allowed the use of the COM estimation from ground reaction forces to be used to calculate the torque about the COM during landing. Assessment of the stabilization time of the toque using methods developed for force signals showed that the torque stabilization time provides further insight than the similar force values when using sequential estimation. The second study examined traditional measures of dynamic stability and the new measure of torque stability during repeated assessment of three common dynamic stability tasks. The purpose of this study was to determine if the measures plateaued, indicating optimal performance had been attained. None of the examined measures exhibited this characteristic, suggesting 30 repeated trials were not adequate to show stability of the measure. A secondary purpose of this study was to examine the correlation of stability measures with landing velocity. The dynamic postural stability index showed moderate agreement with the landing velocity, suggesting use of this measure may require additional considerations to account for landing velocity. Finally, the third study used the studied methods and measures to assess dynamic stability within a concussed population. Static assessments typically used in monitoring recovery were also collected, which showed the previously reported trend that these measures would recover by the time an athlete returned to sport participation. The dynamic measures, expected to show worsened postural control during return to play where static measures could not, did not exhibit any trend indicating compromised dynamic stability. In general, the results of these studies showed that a measure quantifying a stabilization time of torque about the COM provided further insight into planar system stability during dynamic tasks. The estimation of the COM position required for this calculation can be estimated reliably using GRF. Additionally, the repeated assessment of various dynamic stability tasks, and the resulting stability indices, do not present a discernable plateau indicating measure stability. This allows for an adequate amount of practice trials before assessing stability without compromising the measurement due to varying amounts of practice time. Along with this interpretation, landing velocity may affect the dynamic postural stability index, while landing velocity shows no correlation with the measure of torque. This appears to be a strength of the torque measurement, as tasks may not need to be tightly controlled methodologically. Finally, the assessment of concussion using dynamic stability was not improved in comparison to using static assessments. However, further investigation is warranted, as injury rates post-concussion are shown to be elevated