Does intra-individual variability and coordination of chronic ankle instability individuals during squat differ by elevating the rearfoot?
Samson, Christine Olivia
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The combination of joint kinematic variability and time spent in coordination patterns throughout a closed chain task may provide insight to why CAI individuals have a greater risk of posttraumatic osteoarthritis development. The purpose of this dissertation was to identify intra-individual lower extremity kinematic variability and coordination differences between CAI and healthy individuals during normal and elevated rearfoot double-leg squat tasks to identify changes in lower kinematic chain coordination with alleviation of anatomical constraints. Motion capture data were collected as participants performed four trials of 10 squat repetitions for each squat task. Joint and segment angles were processed and analyzed for eight repetitions to determine kinematic variability and segment coordination, respectively. The summated integrated joint angle standard deviation time series across 32 squat repetitions captured total joint kinematic variability throughout a task. Time spent in coordination patterns (e.g., in-phase, anti-phase) throughout the squat for the shank-rearfoot and shank-femur was also identified. Groups were not significantly different with respect to height, mass, age, or physical activity levels (p>.05). Test limb closed chain dorsiflexion identified with the weight bearing lunge test (WBLT) distance was not different between groups, t(26)=1.62, p=.09, d=0.67, (1-β)=0.50. No significant interaction effects between group, task, and anatomical plane were identified for summated joint kinematic variability. However, variability in the sagittal plane was identified as greatest in the knee and hip for both tasks in both groups. No differences in time spent in major coordination patterns of the shank-rearfoot were identified between groups or task in any anatomical plane (p>.05). CAI individuals spent significantly less time in shank-femur in-phase motion than anti-phase motion compared to controls, F(1,26)=6.02, p=0.02, η^2=0.19, (1-β)=0.66, suggesting altered knee neuromuscular control. Both groups had significantly different coordination patterns throughout the squat with the rearfoot elevated compared to flat on the floor (normal). The lack of significant differences in WBLT between groups may explain the similar amounts of variability and changes in coordination between tasks. This study revealed similar squat depths between groups for both tasks but significant differences in shank-femur segment coordination suggests altered neuromuscular control throughout the squat is different for those with CAI.