Thesis Defense Announcement

School of Health Studies announces the Final Thesis Defense of

Rachael Arnwine

for the Degree of Master of Science

April 17, 2019 at 1:00 PM in Fieldhouse, Room 341

Advisor: Douglas Powell

Effects of Arch Height and Arch Stiffness on Knee and Ankle Stiffness During Landing

ABSTRACT: Landing is associated with high external forces applied to the musculoskeletal system. A measure that captures both load magnitude and the musculoskeletal system's response to loading is stiffness. Greater lower limb joint stiffness and joint moments may be contributing factors to traumatic lower extremity injury. It has been postulated that arch height index (AHI) and arch stiffness index (ASI) may be predictors of leg and lower extremity joint stiffness and may be associated with the risk of lower extremity injury. The purpose of this investigation was to evaluate the association between AHI, ASI, and lower extremity stiffness (leg and joint). Sixty recreational athletes performed five step-off landing trials from a height of 40 centimeters. AHI and ASI were calculated. 3D kinematics and ground reaction forces were collected simultaneously. Visual3D was used to calculate ankle, knee, and hip joint angles and moments. Custom software was used to calculate ankle and knee joint stiffness as well as leg stiffness.There were significant differences in AHI (p= 0.00, d = 6.04) and ASI (p= 0.012, d = -1.74) between high and low arched individuals. T-tests showed no significant differences for ankle stiffness (p= 0.154, d = -0.68), knee stiffness (p= 0.149, d = -0.680), or leg stiffness between high and low arched individuals (p= 0.285, d = 0.34). Pearson correlation tests showed no correlation between AHI and ankle stiffness (r = 0.036), knee stiffness (r = -0.165), or leg stiffness (r = 0.312). In addition, there was no correlation between ASI and ankle stiffness (r = 0.083), knee stiffness (r = -0.100), or leg stiffness (r = 0.022). This suggests that there is not a strong association between AHI or ASI and joint or leg stiffness during a step-off landing. We suggest that AHI and ASI may not be significant factors when investigating ankle and knee joint stiffness and leg stiffness during landing. Future research is necessary to further understand the contributions to ankle and knee joint stiffness and leg stiffness during landing.