Lower limb contribution in kayak performance: modelling, simulation and analysis

Lower limb contribution in flatwater kayaking is difficult to quantify experimentally because lower-limbs and pelvis are hidden in the kayak. A computer simulation model was developed to assess the lower limb contribution to kayak performance. Three simulated movements were compared in terms of paddle tip velocity, force impulse, and mechanical work. The pelvis motion increased the paddle tip velocity by 0.15 m s(-1) at the stroke beginning and 0.34 m s(-1) afterward. The propulsive impulse was also modified by pelvis rotation with a 3.5 N s increase per stroke. For a set performance, the co-ordination involving the lower limbs decreased the mechanical work by 20 J. The above results were obtained by modelling the Ergometer-Athlete-Paddle {EAP} system using 18 bodies and 31 degrees of freedom. The motion capture data were transformed in generalized coordinate time histories by solving an inverse kinematics problem with optimization in order to assess both lower limb and upper limb positions and produce a cyclic motion. Then the {EAP} was simulated based on Lagrangian dynamics with Lagrange multipliers to introduce the paddle forces. Finally, the joint torques were calculated by solving an inverse dynamics problem with optimization in order to ensure a good distribution of lower limbs actuating torques.