Author(s): YUSEN, W., HAICHUN, W., CHENG, D., YANGYU, G., XIAOLAN, Z., Institution: BEIJING SPORT UNIVERSITY, Country: CHINA, Abstract-ID: 337

INTRODUCTION:
Ollie has been placed as the focal point since its representativeness of low level stunts among all skateboarding maneuvers. Accompanying by technique advancing, the multi-body dynamics model was used for detecting Ollie’s jumping action as well. As previous studies reported that shock attenuation can be realized by changing the shape of longitudinal and transverse arch. However, we don’t know whether the metatarsal’s (MT) role and trend in skateboarding are consistent with other sport ls. Accordingly, finite element method was used in this study on the purpose of investigating internal movement and shock-absorbing mechanism of MT in the Ollie landing motion.
METHODS:
A male skateboarder was recruited. The experimental shoes and skateboard are ES skateboard shoes and 8.0-inch street skateboard. The program was approved by the Ethics Committee of Beijing Sport University (2023143H). We used the CT scanner and the 3D laser scanner to acquire the image. Model extraction and restoration were performed at Mimics 21.0 and Geomagic Studio 2013. The model was verified by comparing the plantar pressure of simulation with the measurement of natural standing condition. The subject performed Ollie movement via the Pedar system to obtain the planter force-time curve (F-T curve). the F-T curve through removing the noise directly, three characteristics were found: the moment of touching the ground (T1), the moment of the peak of the plantar force (T2) and the moment of the trough of the plantar force (T3). Loading the data into the FE model and restore the Ollie landing action.
RESULTS:
The result error was approximately 6.98% comparing the measuring outcome and model simulation of peak plantar pressure when subject stood on the skateboard, which were 125kPa and 116.27kPa respectively, and all positioned in the heel. The largest figure of stress peak (1.126MPa) at T1 occurred in MT3. The stress of MT4 at both T2 and T3 were the highest, peaking at 23.211 MPa and 29.161 MPa respectively. The changing trends of peak stress of MTs were the same, namely the tendency of MT1 to MT5 were gradually increasing from T1 to T3 and eventually peaking at T3. During landing, the twisting angles of MT1 and MT2 changed greatly, the medial part of the foot moved downward, and the transverse arch of the foot collapsed. This alteration represented that MTs were withstanding changed impact force at T2 and T3. When cushioning, the sagittal plane of MT2, MT3 and MT4 shifted more. The displacement of medial MT1 was greater than that of lateral MT5, accompanied by midfoot and medial downward displacement and transverse arch collapse.
CONCLUSION:
During Ollie landing, the transverse arch of the foot has tendons to collapse, by sinking the medial metatarsal bone to achieve the purpose of delaying the impact. The main load-bearing site is in the middle metatarsal bone(MT2, MT3,MT4), which is subjected to a large vertical axial load. The first and fifth metatarsal bones are mainly auxiliary to prevent lateral migration.