Vertical ground reaction force asymmetries in male and female athletes across four athletic tasks
LE3 .A278 2021
Bachelor of Science
Motor asymmetries are naturally occurring phenomena that may result from longstanding participation in sport and athletic activity. Ground reaction forces (GRF) produced by athletes through tasks such as cutting, running, and landing on one or two legs yield various levels of asymmetry when comparing one leg to the other. Certain levels of asymmetry may increase the risk of injury to an athlete if not addressed and remediated. The purpose of this study was to identify and compare the level of asymmetries across various athletic tasks in males and females of contact (male football and female rugby), soccer, and basketball sport backgrounds while qualitatively comparing three different symmetry indices including; the Symmetry Index (SI), Symmetry Angle (SA), and Normalized Symmetry Index (NSI). Data were collected in the John MacIntyre motion Laboratory of Applied Biomechanics (mLAB) located in the Athletic Complex of Acadia University in Wolfville, Nova Scotia, Canada. The cohorts included: male contact (football), female contact (rugby), male soccer, female soccer, male basketball, and female basketball. The athletes performed a sub-maximal run, an unanticipated cut to change direction,and double leg and single leg drop landings. Data collection involved capturing muscle activity, ground reaction forces, and 3D marker position for each participant, however only vertical forces were analyzed in this study. Using MATLAB, symmetry index values were tabulated for the peak vertical ground reaction force (vGRF) through the stance phases of the run and cut, and the landing phases of a double and single leg drop jumps, referred to as double leg landings and single leg landings. RStudio was used to calculate means and standard deviations and then create two-factor gamma generalized linear models (GLM) for each task for sex and sport. A Wald chi- squared test was performed on the GLMs to identify significant main or interaction effects. If a significant effect was found (p < 0.05), a pairwise comparison test was conducted using the Tukey p-value adjustment method to reveal the levels of the main effects. This study found that through a cutting and running task, males produced significantly greater asymmetries than females. In the cutting task, contact athletes produced significantly greater asymmetries than basketball athletes. In the running task, basketball athletes produced significantly greater asymmetries than soccer athletes. Significant differences were not evident through the double leg landing and single leg landing tasks. The present findings may help address the injury implications of vGRF asymmetries within high school and university athletes, while providing a qualitative understanding of various symmetry indices.
The author grants permission to the University Librarian at Acadia University to reproduce, loan or distribute copies of my thesis in microform, paper or electronic formats on a non-profit basis. The author retains the copyright of the thesis.