Low back injuries are a significant problem in elite rowers (Hickey, 1997). The Mechanical load generated at the spine during rowing was found to be considerably higher than in other sportive movements (Morris, 2000). Investigations show that the amount of lumbar flexion occurring during rowing, might influence the possibility of injury (Jillian, 2003). Biomechanical analysis of internal joint forces and torques of rowers are rarely found in today`s literature. The aim of this study is to calculate the internal joint forces and torques with a 3D computer model. Based on these calculated joint torques and forces, the individual rowing technique of the athlete is optimized using a computer simulation. The optimized technique minimizes the spinal load in the computer model, while the power output is maximized. Methods The first step of a 3D motional analysis of two elite rowers was performed on a rowing ergometer. The rowing strikes were performed with a maximal power output. Pulling forces were recorded with a force transducer. The trials were digitized using a 3D inverse dynamic marker set (SIMI motion, Munich, Germany). Model joint forces and torques for each of the athlete were calculated using a 3D rigid body model (Fig. 1). This rigid body model consists of 14 segments, connected by 12 joints. Since rowers show individual force patterns, the model is scaled to the individual athlete. Segment mass, inertia, and joint positions of the model are individually calculated for each subject in the Hanavan model. In the second step, the resultant muscle joint torques obtained in the experiment were optimized with a constrained based optimizer (Matlab, Mathworks, Natick, USA) so that the spinal shear force is minimized and the power output is maximized. The shear force is the joint reaction force perpendicular to the spine at the level L4-5 and L5-S1. Results Both athletes show individual joint force and torque patterns. Optimization of the rowing technique leads in both cases to less joint torques in the spinal joints, which is associated with a lower lumbar flexion angle. Discussion/Conclusion These preliminary results demonstrate that the 3D model is useful to quantify internal loads of the rowing athletes. As expected from the literature a large variability exists in the joint angles, forces and torques between both subjects. Optimization leads to a slightly different rowing technique, transferring more joint power to other than the lumbar joints. This model approach gives the coach a helpful tool to quantify the technique in terms of their maximal power production and minimal spine load.
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