Jürgen Edelmann-Nusser

Modeling and Prediction of Competitive Performance in Swimming Upon Neural Networks

The purpose of the paper is to demonstrate that the performance of an elite female swimmer in the finals of the 200-m backstroke at the Olympic Games 2000 in Sydney can be predicted by means of the nonlinear mathematical method of artificial neural networks (Multi-Layer Perceptrons). The data con-sisted of the performance output of 19 competitions (200-m backstroke) prior to the Olympics and the training input data of the last 4 weeks prior to each competition. Multi-Layer Perceptrons with 10 input neurons, 2 hidden neuron, and 1 output neuron were used. Since the data of 19 competitions are insuffi-cient to train such networks, the training input and competition data of another athlete were used in the training processes of the neural networks to pre-train the neural networks. The neural models were validated by the “leave-one-out”; method, then the neural models were used to predict the Olympic competitive performance. The results show that the modeling was very precise; the error of the prediction was only 0.05 s, with a total swim time of 2:12.64 min:s.

Determination of three-dimensional joint loading within the lower extremities in snowboarding:

In the biomechanical literature only a few studies are available focusing on the determination of joint loading within the lower extremities in snowboarding. These studies are limited to analysis in a restricted capture volume due to the use of optical video-based systems. To overcome this restriction the aim of the present study was to develop a method to determine net joint moments within the lower extremities in snowboarding for complete measurement runs. An experienced snowboarder performed several runs equipped with two custom-made force plates as well as a full-body inertial measurement system. A rigid, multi-segment model was developed to describe the motion and loads within the lower extremities. This model is based on an existing lower-body model and designed to be run by the OpenSim software package. Measured kinetic and kinematic data were imported into the OpenSim program and inverse dynamic calculations were performed. The results illustrate the potential of the developed method for the determination of joint loadings within the lower extremities for complete measurement runs in a real snowboarding environment. The calculated net joint moments of force are reasonable in comparison to the data presented in the literature. A good reliability of the method seems to be indicated by the low data variation between different turns. Due to the unknown accuracy of this method the application for inter-individual studies as well as studies of injury mechanisms may be limited. For intra-individual studies comparing different snowboarding techniques as well as different snowboard equipment the method seems to be beneficial. The validity of the method needs to be studied further.

Optimisation of a bow riser using the autogenetic design theory

The autogenetic design theory (ADT) is an approach aiming at modelling and supporting the design activity as the primary activity within the product development process. A new product development model must consider the mixed process of searching, adopting existing knowledge, learning, evaluating, selecting, and combining. Such methodologies are also found in biological evolution (the corresponding activities there are replication, evaluation, selection, recombination). The ADT is based on the idea that new solutions (individuals) can be developed by the use of evolutionary methodologies. Under the pressure of selection, good properties of the preceding solutions (parents) are passed on to the succeeding solutions (children). \noindent Typically, the riser of a recurve bow has to be of light weight and high stiffness. The challenge for the designer is to find the solution which best meets both demands. Due to the large number of technically possible designs, it is inefficient to model and evaluate more than a few designs manually. By applying the ADT, the designer has the ability to consider a large number of possible designs, which raises the probability of finding the best possible solution. In this case, the ADT allows us to reduce the mass by 22% while keeping the stiffness at the same level.

Spectral parameters of surface electromyography and performance in swim bench exercises during the training of elite and junior swimmers

Abstract Spectral parameters of surface electromyography (EMG) are used to assess intramuscular coordination in terms of fatigue and motor unit recruitment. The aim of the present study was to examine changes in performance and EMG spectral parameters of the propulsive muscles during a swim bench exercise in swimmers to determine the intra-individual effects of different training periods in the normal training process. Ten swimmers of different ages and standards were investigated in a longitudinal study. Electromyograms of the relevant muscles (triceps longum, triceps lateralis, and latissimus dorsi) were recorded during the tests, and spectral parameters calculated using time-variant spectral analysis. In the elite swimmers, we observed variation in performance throughout the training season with respect to training load, whereas for the junior swimmers there was a trend to improve performances irrespective of training load. Correlations with performance were observed for the median frequencies of the triceps longus for the elite athletes. Performances and frequencies were increased in the taper period, whereas they were reduced after periods of high training loads. For the junior swimmers, no such correlations were observed. Based on our results, spectral parameters could provide information about the fatigue of the neuromuscular system of elite swimmers during periods of high training loads and enhanced intramuscular coordination in the taper period before competition.

Examination of the reliability of an inertial sensor-based gait analysis system

Abstract Gait analysis is an important and useful part of the daily therapeutic routine. InvestiGAIT, an inertial sensor-based system, was developed for using in different research projects with a changing number and position of sensors and because commercial systems do not capture the motion of the upper body. The current study is designed to evaluate the reliability of InvestiGAIT consisting of four off-the-shelf inertial sensors and in-house capturing and analysis software. Besides the determination of standard gait parameters, the motion of the upper body (pelvis and spine) can be investigated. Kinematic data of 25 healthy individuals (age: 25.6±3.3 years) were collected using a test-retest design with 1 week between measurement sessions. We calculated different parameters for absolute [e.g. limits of agreement (LoA)] and relative reliability [intraclass correlation coefficients (ICC)]. Our results show excellent ICC values for most of the gait parameters. Midswing height (MH), height difference (HD) of initial contact (IC) and terminal contact (TC) and stride length (SL) are the gait parameters, which did not exhibit acceptable values representing absolute reliability. Moreover, the parameters derived from the motion of the upper body (pelvis and spine) show excellent ICC values or high correlations. Our results indicate that InvestiGAIT is suitable for reliable measurement of almost all the considered gait parameters.

Lightweight design optimization of a Bow Riser in Olympic Archery applying evolutionary computing

Recurve bows that are used in competitions like the Olympic Games are high-technology products. Good risers are lightweight but retain a high stiffness. The aim of this study was to design a riser with a stiffness comparable to that of the lightest riser currently used by the archers of the German National Archery Team, but with a considerably reduced weight. We computed the loads that are applied to a riser of a drawn recurve bow (the RADIAN model used by the German team) and created a 3-D solid CAD model of a riser with 24 variable parameters. We used evolutionary computing to optimize the 24 parameters of the model according to these criteria. We selected the most optimal riser out of the 1650 CAD models generated, manufactured it, and had it tested by three archers of the German National Archery Team. The mass of our manufactured riser is 871g, which is 243g or 22% less mass than the RADIAN riser.

Examination of a Swimming Dummy’s Flow Field Using Laser Doppler Velocimetry

Motivated by the fact that the evaluation of different swim suit designs produced inconsistent results, this study takes a new approach. In this pilot study, the Laser Doppler Velocimetry Method was applied to examine the flow field around a water rescue dummy, which was mounted in a swimming flume. Laser Doppler Velocimetry allows velocity measurement of particles that move with the water flow. Measurements can be taken from a distance to the object of about 600 mm. Through this, interference of the measurement devices with the water flow can be avoided. It was found that this approach has the potential to analyze a swimmer’s flow field, and the horizontal component of the flow velocity was determined at around 5000 positions. Limitations were the minimum spatial resolution of 1 millimeter and the time-consuming data collection due to the small number of tracer particles inside the water. It is intended to use this test set up in the future to investigate the effects of different swimsuit designs with respect to a swimmer’s flow field.

Use of the Infrared Based Motion Capture System AS 200 in Sport Science

In the field of optical measurement systems there are two main possibilities. On the one hand collecting data by using normal standardized video cameras is very popular. On the other hand measurement systems based on infrared cameras become more and more important. Comparing these two optical measurement systems there are different features in quality making them either attractive or not. Regarding video-systems, the recording of the movement is very simple but the analysis is very time-consuming. In contrast to the normal video camera-systems the infrared-based systems have the advantage to provide kinematic parameters in real-time, making it very interesting for scientific research as well as coaches. The AS 200 (LUK Otronic) for instance is an active infrared-based measurement system which consists of three infrared cameras fixed on a beam. Therefore, it is possible to install this system very fast and simply. Possible fields of application seem to be: biomechanical analysis of sport movements and medical researches. This study will present an evaluation and different options how to applicate the AS 200, especially fast movements in sport.

Analyzing the Transfemoral Amputee Gait using Inertial Sensors - Identifying Gait Parameters for Investigating the Symmetry of Gait - A Pilot Study

The amputation of a lower limb is a drastic event and it completely changes the life of the person. Current development of prosthesis is already advanced, but most of the affected persons suffer from changes in the gait which are visible to the general public. The gait of transfemoral amputees was investigated in the laboratory environment and is called asymmetric due to different facts: shorter step length, smaller velocity and smaller cadence. The use of mobile inertial sensors can be supportive in the rehabilitation process of these patients. That is why a pilot study is conducted to evaluate the gait of transfemoral amputees and compare their gait parameters with those of the healthy subjects. The purpose of the investigation is to identify gait parameters showing the asymmetric properties of the amputees gait. Eight parameters seem to be distinctive

Evaluation und Test

Die Evaluationsphase ist im Rahmen der Produktentwicklung von hoher Bedeutung, denn hier werden die Gute, die Qualitat oder bestimmte Eigenschaften eines Produkts mittels entsprechender Tests nachgewiesen und es wird uberpruft, ob ein Produkt die Erwartungen, die es erfullen soll, auch tatsachlich erfullen kann