Biomechanical assessment of the shoe-surfact interface during the golf swing
A successful golf swing is dependent on the performance of a complex sequential action. This movement involves the feet, knees, rotation of the hips and trunk, which result in a transmission of forces and torques between the feet/shoes and the ground (Williams and Sih, 1998). The aim of this thesis was to investigate golf shoe interface aspects relevant to the golf swing process. One flat-soled, one traditional and three alternative spiked golf shoe sole interfaces were evaluated. Using a mechanical traction-testing device, specific linear forces and rotational torques were applied to the forefoot and whole-foot of the five different golf shoe sole interface designs on a grass covered force platform. Greater linear and rotational ground action forces were identified within the traditional sole (whole-foot limiting friction 1.01) and alternative sole conditions (whole-foot limiting friction Blue 1.00, Red 1.02, Yellow 1.01) when compared to a flat-soled shoe (whole-foot limiting friction 0.88). The traditional shoe was also identified to frequently produce greater friction (forefoot limiting friction 0.97) in comparison to the alternative shoe soles (forefoot limiting friction Blue 0.92, Red 0.91, Yellow 0.91). Due to the mechanical nature of the study it was important to gain an understanding of how the golf shoe sole interface interacted with the ground and if between-shoe differences were repeated when subjected to dynamic human movement during the golf swing. Dynamic analysis of the five soles identified two between shoe-sole differences (P = <.OS); Driver back foot Tz range (BW.m) (Traditional shoe (IS.98 ± 1.11) was significantly different to the Blue alternative (12.77 ± .83) and flat-soled shoe (12.73 ± .8S)); and 7iron front foot, Mz maximum time (s) (Flat-soled shoe (1.39 ± .02) was significantly different to Blue (1.72 ± .03) Red (1.71 ± .03) and Yellow (1.72 ± .04) alternative spiked shoes). The low handicap group (0-7) produced significantly slower weight transfer times (s) when compared to the medium (8-14) and high (15+) groups within all club conditions (3iron Low 0.73 ± .03, Medium 0.43 ± .02 and High 0.41 ± .02; 7iron Low 0.76 ± .01 Medium 0.S4 ± .01 and High 0.54 ± .01; Driver Low 0.70 ± .01, Medium 0.48 ± .01 and High 0.43 ± .01). However, no significant differences in forces or torques were identified between handicap groups. The findings contradict the previous mechanical testing results concluding mechanical traction tests are not an appropriate test of between shoe differences when relating the findings to the golf swing. The differences in forces created between the shoe and ground identified between the mechanical and dynamic studies was a result of the adaptation by the golfer to the footwear condition. Dynamic in-shoe pressure analysis identified regional pressures created between the golfer and shoe throughout the swing process. The highest peak pressures (N/cm2 ) were associated with the lateral regions of the front-foot from the point of ball impact (Front foot Traditional (R5) 114.33 ± 6.29 N/cm2 Back foot Traditional (R5) 7.18 ± 1.07 N/cm2) supporting previous kinematic and ground action force findings. The traditional spiked shoe produced greater in-shoe pressures within the front foot lateral mid-foot region however all sole conditions provided significantly higher pressures within specific in-shoe regions at different stages of the swing process. The comparable between shoe findings support the previous dynamic findings. The thesis enhanced current understanding of between shoe-ground and shoe-golfer interactions. Different demands were placed on the front and back shoes during the golf swing highlighting the need for asymmetrical shoe sole designs. Limited differences were identified between the different shoe sole interface designs, concluding that golf shoe interface designs are not effective for the demands of the golf swing, subsequently shoe outsole modifications were suggested.