A New Testing Device for the Role of the Trunk in Force Production and in Balance Control in Disabled Sitting Athletes

In cross-country sit-skiing all athletes compete in a sitting position, but some of them have the ability to control their trunk more than others. The trunk plays an essential role in two performance determinants: propulsion generation and balance maintenance. The aim of the study is to design a new testing device assessing athletes’ responses to these propulsion determinants. The new device was composed of a seat surrounded by a sensorized aluminum frame. To assess propulsion generation, two force sensors were mounted in the anterior and posterior side of the frame, while two force sensors were embedded in two ropes elongated from the top of the frame. To measure trunk control, the device was mounted on an electrically-driven sledge, which can be moved in anterior and posterior direction giving unpredictable balance perturbations to the athlete. In the paper a pilot test is presented. One athlete with low trunk control level was tested. The main results were: (1) no drawbacks related to discomfort or pain, (2) lower level of generated force without back support compared to the condition with back support, and (3) higher trunk range of motion and trunk angular velocity in response to unpredictable balance perturbations when the acceleration of the perturbations increased. These preliminary results suggest that the new device is suitable for testing sitting athletes. Future tests with a higher number of athletes with different levels of disability can give valuable new information, which can be used for evidence-based classification.