Leg extension is a multi-articular movement allowing flexibility of muscular activation and control. Therefore, joint loadings during leg press exercise can only be estimated using the whole reaction force vector together with the leg posture. A dynamic model of the musculoskeletal system as well as experimental data from a diagonal leg press are used to investigate external knee joint loadings and the influence of different orientations of the foot plate. Varying orientation in sagittal plane affects ankle, knee and hip loadings by changing the leg posture and the direction of the resulting force vector. Different orientations in frontal plane move the center of pressure of the force vector across the foot and thus change knee adduction and abduction moments. The results in this paper indicate, that high forces, which are required for an effective training, can be controlled using the foot orientation as manipulated variable. Thereby, unphysiological loadings and training-induced damage can be avoided.
In remote sensing data, trees have a low interspecies variability and show a high variability within the tree species. Therefore, specific features that distinguish between unique properties of two tree species are required for a single tree based genera classification. To improve classification results, the suitability of seven surface roughness features, calculated on single tree crown regions, is studied. The algorithms developed to provide roughness parameters can be validated and prototyped in a Virtual Forest testbed. The features are extracted from a normalized digital surface model with a resolution of 0.4m per pixel. Within the test area of 340km 2 more than 4000 single trees of eleven different species and additionally 200 buildings are available as reference data. Technical standards define several parameters to describe surface properties. These roughness features are evaluated in the context of single tree crowns. All of these features are based on the deviation of the height values of the tree crown to its mean height. As an additional feature the relationship between the crown's surface area and its occupied ground area is used. The evaluation results of these features regarding the discrimination of tree species on different levels -eleven single tree species, seven tree classes, deciduous and coniferous -and also towards discrimination of trees from buildings will be presented.
ZusammenfassungNeuromuskuläres Aufbautraining der Beinstrecker ist ein wichtiger Bestandteil in der Rehabilitation und Prävention von Muskel-Skelett-Erkrankungen. Effektives Training erfordert hohe Muskelkräfte, die gleichzeitig hohe Belastungen von bereits geschädigten Strukturen bedeuten. Um trainingsinduzierte Schädigungen zu vermeiden, müssen diese Kräfte kontrolliert werden. Mit heutigen Trainingsgeräten können diese Ziele allerdings nicht erreicht werden. Für ein sicheres und effektives Training sollen durch den Einsatz der Robotik, Sensorik, eines Regelkreises sowie Muskel-Skelett-Modellen Belastungen am Zielgewebe direkt berechnet und kontrolliert werden. Auf Basis zweier Vorstudien zu möglichen Stellgrößen wird der Aufbau eines robotischen Systems vorgestellt, das sowohl für Forschungszwecke als auch zur Entwicklung neuartiger Trainingsgeräte verwendet werden kann.
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