Performance determinants and leg kinematics in the BMX supercross start
Keywords:bicycle motocross, leg motion, torque, power, joint angles, joint power, kinematic, kinetic
AbstractIn competitive BMX racing, a fast start, that is, the shortest possible elapsed time and the highest possible instantaneous velocity at the end of the starting phase, is crucial for obtaining a favourable position in the middle portion of the race and the best possible final ranking. This study aimed first to evaluate several influencing factors for their relative importance in determining starting performance in competitive BMX racers. Also, this study describes basic leg kinematics during the first few pedal strokes of the starting phase. Subjects performed practice starts on a supercross ramp while various kinematic and kinetic parameters were obtained using a modified powermeter crank and a 3-d motion capture system. Data were analyzed with linear regression with starting performance as the output. The results show that an early turnaround during the preparation maneuver (countermovement) prior to the gat drop and a powerful first pedal stroke, with both a high torque and equivalent cadence, have the most influence on overall starting performance. End velocity is also related to attained peak cadence and the torque at peak cadence. Regarding leg kinematics, extension velocities are similar to ballistic jumps with relatively high loads. Thus, BMX racers should focus technical training on a quick and early turnaround in the preparation maneuver and strength training should be focused on developing strength and power at relatively high loads.
How to Cite
Copyright (c) 2020 Journal of Science and Cycling
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.
Authors contributing to Journal of Science and Cycling agree to publish their articles under a Creative Commons CC-BY 4.0 license, allowing third parties to copy and redistribute the material in any medium or format, and to remix, transform, and build upon the material, for any purpose, even commercially, under the condition that appropriate credit is given, that a link to the license is provided, and that you indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
Authors retain copyright of their work, with first publication rights granted to Cycling Research Center
Authors reatin copyright of their work. The Effect of Open Access