Gunnar B. J. Andersson

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The motions, forces, and moments at the major joints of the lower limbs of ten men ascending and descending stairs were analyzed using an optoelectronic system, a force-plate, and electromyography. The mean values for the maximum sagittalplane motions of the hip, knee, and ankle were 42, 88, and 27 degrees, respectively. The mean maximum net(More)
Recent epidemiological studies have indicated high risk factors for persons exposed to vibrations. We measured the in vivo responses of the lumbar vertebrae and sacrum of five volunteers who were subjected to pure sinusoidal vertical vibrations in the seated position. Two acceleration amplitudes were used, one and three meters per second squared, with(More)
The mechanics of the lower limb were analyzed in young, adult normal subjects when rising from a seated position. Limb mechanics were described in terms of flexion-extension motion and moments at the hip, knee and ankle while rising from four seat heights corresponding to 65, 80, 100, and 115% of the subject's knee joint height. The results indicate that(More)
Flexion-extension moments acting at the L5/S1 level and hip joints were calculated using three different techniques; a pure static analysis, a static analysis including the inertial force of the load, and a dynamic analysis. Ten subjects participated in the study and were asked to lift a box weighing either 50 N or 150 N, using a freestyle technique. The(More)
Optimization-based models for prediction of muscle forces in the lumbar region of the torso are used to estimate the forces acting on spinal motion segments, especially for asymmetric tasks. The objectives of this study were to determine (a) which of four torso model formulations best predicted the electromyographic data, (b) the difference in muscular(More)
The influence of backrest inclination and lumbar support on the shape of the lumbar spine in sitting positions has been studied radiographically on 38 healthy subjects. Four angles of backrest inclination and four different sizes of lumbar support were studied. In addition, the lumbar support was placed at three different lumbar levels. When sitting down(More)
The purpose of this study was to analyse the influence of load knowledge on lifting technique. Ten men lifted a box containing either no weight or weights of 150, 250 or 300 N with and without knowledge of what was inside the box. The kinetics and kinematics of the lift were analysed using a force plate, an optoelectronic motion analysis system, and a rigid(More)
The current study investigated mechanical predictors for the development of adjacent disc degeneration. A 3-D finite element model of a lumbar spine was modified to simulate two grades of degeneration at the L4-L5 disc. Degeneration was modeled by changes in geometry and material properties. All models were subjected to follower preloads of 800N and moment(More)
The trunk muscles of the lumbar region were studied using magnetic resonance imaging (MRI) in five male volunteers placed in neutral and in two twisted postures. Using a CAD digitizing system, the positions of trunk muscle centroids and the cross-sectional areas of these muscles were measured from the transverse scans at 1 cm intervals from L2 to S1. Muscle(More)