Estimation of the energy loss at the blades in rowing: Common assumptions revisited

Abstract

In rowing, power is inevitably lost as kinetic energy is imparted to the water during push-off with the blades. Power loss is estimated from reconstructed blade kinetics and kinematics. Traditionally, it is assumed that the oar is completely rigid and that force acts strictly perpendicular to the blade. The aim of the present study was to evaluate how reconstructed blade kinematics, kinetics, and average power loss are affected by these assumptions. A calibration experiment with instrumented oars and oarlocks was performed to establish relations between measured signals and oar deformation and blade force. Next, an on-water experiment was performed with a single female world-class rower rowing at constant racing pace in an instrumented scull. Blade kinematics, kinetics, and power loss under different assumptions (rigid versus deformable oars; absence or presence of a blade force component parallel to the oar) were reconstructed. Estimated power losses at the blades are 18% higher when parallel blade force is incorporated. Incorporating oar deformation affects reconstructed blade kinematics and instantaneous power loss, but has no effect on estimation of power losses at the blades. Assumptions on oar deformation and blade force direction have implications for the reconstructed blade kinetics and kinematics. Neglecting parallel blade forces leads to a substantial underestimation of power losses at the blades.

Keywords:

• Blade force
• oar deformation
• efficiency of propulsion
• aquatic locomotion

Acknowledgements

This study was partially funded by NOC*NSF and TNO. We would like to thank Concept 2 Benelux for unconditionally providing us with a single scull and oars. We would like to thank the technical staff, in particular Erik Clay, Guido Cox and Huybert van der Stadt, for all their efforts concerning the measurement system. We would also like to thank Ellen Maas for her help with the experiments.