INTERACTION EFFECTS OF POSTURE AND UNEVEN GROUND ON ABLE-BODIED WALKING KINETICS

Interactions between trunk orientation and gait kinetics are proposed to be inevitable for maintaining dynamic balance, and these interactions are unknown for walking on uneven ground. The purpose of this study was to investigate the interaction effects of posture (regular erect, 30°, 50° and 70° trunk flexion) and step category (unperturbed, perturbation, pre- and post-perturbation) on able-bodied walking kinetics. Statistical analysis revealed interactions posture×step: with increased trunk flexion, walking on uneven ground exhibited less changes in GRF kinetic parameters relative to upright walking. Pre-adaptations were more pronounced in the approach step to the drop in regular erect gait. It seems that in trunk-flexed gaits trunk is used in a compensatory way during the step-down to accommodate changes in ground level. In conclusion, exploitation of this mechanism resembles the ability of small birds in adjusting their zigzag- like configured legs to cope with changes in ground level

REARFOOT ANGLE VELOCITIES DURING RUNNING - A COMPARISON BETWEEN OPTOELECTRONIC AND GYROSCOPIC MOTION ANALYSIS

The aim of this study was a verification of a gyroscopic measurement device mounted on the heel counter of a running shoe. For this purpose 15 subjects performed 10 running trials in a laboratory environment. Rearfoot angular velocities from the gyroscope were compared qualitatively and quantitatively to rearfoot angular velocities observed with a 3D motion analysis system (VICON). Based on the qualitative and quantitative analysis the results are very good in the sagittal plane, good in the frontal plane and poor in the transverse plane

NEURAL NETWORK MODELING IN SPORT BIOMECHANICS BASED ON THE EXAMPLE OF SHOT-PUT FLIGHT

In this study, a modeling method based on Multi-Layer-Perceptron neural networks (MLP) is presented, using the example of shot-put flight. This method can be used for rapid construction of models. For performance of shot-put, a physical model based on the shots’ equations of motion is easily designed. In this way, an analysis of the shot-put projectory can be used to illustrate the effectiveness of the neural network modeling method. Using the physical model, release data has been determined and altered with random errors such as those introduced by video analysis. A technique for optimal learning with the neural networks has been developed. The resulting MLP models the shot-put flight successfully. The difference between the model’s predicted distance and the distance reached by the physical model are within 2.5%. In conclusion, this method allows rapid creation of models to solve biomechanical problems and can serve as a useful tool for coaches and athletes

Three-dimensional muscle architecture and comprehensive dynamic properties of rabbit gastrocnemius, plantaris and soleus: input for simulation studies

The vastly increasing number of neuro-muscular simulation studies (with increasing numbers of muscles used per simulation) is in sharp contrast to a narrow database of necessary muscle parameters. Simulation results depend heavily on rough parameter estimates often obtained by scaling of one muscle parameter set. However, in vivo muscles differ in their individual properties and architecture. Here we provide a comprehensive dataset of dynamic (n=6 per muscle) and geometric (three-dimensional architecture, n=3 per muscle) muscle properties of the rabbit calf muscles gastrocnemius, plantaris, and soleus. For completeness we provide the dynamic muscle properties for further important shank muscles (flexor digitorum longus, extensor digitorum longus, and tibialis anterior; n=1 per muscle). Maximum shortening velocity (normalized to optimal fiber length) of the gastrocnemius is about twice that of soleus, while plantaris showed an intermediate value. The force-velocity relation is similar for gastrocnemius and plantaris but is much more bent for the soleus. Although the muscles vary greatly in their three-dimensional architecture their mean pennation angle and normalized force-length relationships are almost similar. Forces of the muscles were enhanced in the isometric phase following stretching and were depressed following shortening compared to the corresponding isometric forces. While the enhancement was independent of the ramp velocity, the depression was inversely related to the ramp velocity. The lowest effect strength for soleus supports the idea that these effects adapt to muscle function. The careful acquisition of typical dynamical parameters (e.g. force-length and force-velocity relations, force elongation relations of passive components), enhancement and depression effects, and 3D muscle architecture of calf muscles provides valuable comprehensive datasets for e.g. simulations with neuro-muscular models, development of more realistic muscle models, or simulation of muscle packages