Arnold Baca

Rapid Feedback Systems for Elite Sports Training

Advances in information technology have let computer scientists and engineers develop sports-specific feedback systems in cooperation with biomechanists, physiologists, sport psychologists, and strength and conditioning specialists. These feedback systems incorporate embedded sensors and devices into the sport equipment or use sensors attached to the athlete to acquire biomechanical, physiological, and cognitive and behavioral parameter values of the exercise performed. We believe that such an adaptation could be productive because athletes could better compare performance in training and competition. Sports broadcasts could even use the data we acquire to help illustrate informative segments

Accuracy of the LPM tracking system considering dynamic position changes

Abstract This study investigates the accuracy of the tracking system LPM (Local Position Measurement). The goal was to determine detailed error values of the system in the context of sports performance analyses. Six moderately trained male soccer players (amateur level) performed 276 runs on three different courses at six different speeds. Additionally, ten small-sided game plays were carried out. All runs and game plays were recorded with the LPM tracking system and the motion capture system VICON simultaneously. VICON served as the reference system. The absolute error of all LPM position estimations was on average 23.4±20.7 cm. The estimation for average velocities varied between 0.01 km h−1 and 0.23 km h−1, the maximum speed estimations differed by up to 2.71 km h−1. In addition, the results showed that the accuracy of the LPM system is highly dependent on the instantaneous dynamics of the player and decreases in the margins of the observation field. These dependencies were quantified. Considering commonly used applications of position tracking systems in sports (Leser, Ogris, & Baca, 2011), the accuracy of LPM is acceptable for position and velocity estimations. The system provides valuable results for average velocities but seems to be far less reliable when dealing with high dynamic movements and measuring instantaneous velocities.

A Server-Based Mobile Coaching System

A prototype system for monitoring, transmitting and processing performance data in sports for the purpose of providing feedback has been developed. During training, athletes are equipped with a mobile device and wireless sensors using the ANT protocol in order to acquire biomechanical, physiological and other sports specific parameters. The measured data is buffered locally and forwarded via the Internet to a server. The server provides experts (coaches, biomechanists, sports medicine specialists etc.) with remote data access, analysis and (partly automated) feedback routines. In this way, experts are able to analyze the athlete’s performance and return individual feedback messages from remote locations.

Local Positioning Systems in (Game) Sports

Position data of players and athletes are widely used in sports performance analysis for measuring the amounts of physical activities as well as for tactical assessments in game sports. However, positioning sensing systems are applied in sports as tools to gain objective information of sports behavior rather than as components of intelligent spaces (IS). The paper outlines the idea of IS for the sports context with special focus to game sports and how intelligent sports feedback systems can benefit from IS. Henceforth, the most common location sensing techniques used in sports and their practical application are reviewed, as location is among the most important enabling techniques for IS. Furthermore, the article exemplifies the idea of IS in sports on two applications.

Stability analysis of motion patterns in biathlon shooting

The aim of this study was to analyze the stability of the aiming process of elite biathlon athletes. Nine elite athletes performed four series of five shots onto the same target and onto targets next to each other in a shooting hall. A video-based system reconstructed the horizontal and vertical motion of the muzzle. The time period starting after repeating the rifle and ending with the shot was divided in 10 intervals of equal duration. Eight kinematic parameters describing the motion in these intervals were calculated. Based on the parameter values obtained a special variant of an artificial network of type SOM (self-organizing map) was trained. Similar neurons were combined to clusters. For each shot the 10 data sets describing the aiming process were then mapped to the corresponding neurons. The sequence of the related clusters in the respective succession was used as representation of the complex aiming motion. In a second processing step types of shots were identified applying a second net. A more stable pattern could be inferred for the members of the national squad compared to the biathletes classified in the next best performance level. Only small differences between the two shooting conditions could be observed.

Precise determination of anthropometric dimensions by means of image processing methods for estimating human body segment parameter values

A method has been developed for the precise determination of anthropometric dimensions from the video images of four different body configurations. High precision is achieved by incorporating techniques for finding the location of object boundaries with sub-pixel accuracy, the implementation of calibration algorithms, and by taking into account the varying distances of the body segments from the recording camera. The system allows automatic segment boundary identification from the video image, if the boundaries are marked on the subject by black ribbons. In connection with the mathematical finite-mass-element segment model of Hatze, body segment parameters (volumes, masses, the three principal moments of inertia, the three local coordinates of the segmental mass centers etc.) can be computed by using the anthropometric data determined videometrically as input data. Compared to other, recently published video-based systems for the estimation of the inertial properties of body segments, the present algorithms reduce errors originating from optical distortions, inaccurate edge-detection procedures, and user-specified upper and lower segment boundaries or threshold levels for the edge-detection. The video-based estimation of human body segment parameters is especially useful in situations where ease of application and rapid availability of comparatively precise parameter values are of importance.

Fuzzy Logic in Sports: A Review and an Illustrative Case Study in the Field of Strength Training

ABSTRACT As a special form of probabilistic reasoning, the fuzzy logic concept allows the effective realization of approximate, vague, uncertain, dynamic, continuous and, at the same time, more realistic conditions, which are closer to the actual physical world and human thinking. This many-valued idea involves the definition of fuzzy sets and rules as well membership functions. These techniques allow the mapping of classes of objects not only – according to the binary logic – to false (0) and true (1) but also to intermediate values in between. Based on this theorem, the particular purpose of this paper was to propose a fuzzy logic approach for the evaluation of strength training exercises. The motivation for the present study arose from previous research done in the area of artificial intelligence (AI) in sports, the effective number of multidisciplinary solutions integrating fuzzy logic methodologies and the lack of applications in the fields of sport and especially strength training. The conception takes into account gathered data from sensor-equipped machines as well as recommended suggestions and criteria regarding a proper execution. The final aim is to integrate the designed procedures into a computer-based coaching framework, returning automated feedback on the performed technique.

Feedback Systems in Rowing

On-land feedback devices using rowing ergometers provide an alternative for on-water systems. In order not to draw incorrect conclusions it is essential to compare the rowers’ technique in the boat to that on the ergometer. Units for measuring reaction forces in the boat and at the ergometer have been constructed. Similarities in the reaction forces at the foot stretcher could be found for elite rowers.

Muscle co-contraction around the knee when walking with unstable shoes

Walking with unstable shoes has been discussed to decrease joint loading. Typical estimates of joint loading using an inverse dynamic approach only account for net joint moments, not considering the potential role of muscular co-contraction. Therefore, the purpose of this study was to compare muscular co-contraction levels when walking with two different unstable shoe constructions (rocker-bottom and toning shoes) compared to walking with regular shoes. For each shoe condition, 12 healthy subjects walked with both, a regular shoe and with an unstable shoe at self-selected walking speed at a 10-m walkway. Surface EMG data of selected muscles were recorded and time normalized for calculating co-contraction indices (CCI) for opposing muscle groups. Results showed an increase of co-contraction primarily for vastii and gastrocnemius muscles for the first and second half of stance when walking with an unstable shoe construction. Therefore, when using an inverse dynamic approach to analyze joint loading differences between regular shoes and unstable shoes, one should be cautious in interpreting the data, as these methods base their estimates of joint moments upon the net joint torque.

Accuracy of an UWB-based position tracking system used for time-motion analyses in game sports

Abstract The main aim of this study was to determine the accuracy of the ultra-wideband (UWB)-based positioning system Ubisense, which is used for time-motion analysis in sports. Furthermore, some alternatives for positioning the systems transponders on the atheletes, as well as the accuracy depending on the location of measurement, were tested. Therefore, in a pre-study, some basic issues were examined (measurement assumptions and consistency and location of the systems transponder used for position detection), and position measurements at the borders and in the centre of a basketball field were performed. In the main study, 13 male basketball players (15.8 years ± 0.6; 187.9 height ± 3.4; 77.5 weight ± 3.7), equipped with a Ubisense transponder mounted on top of their heads, handled a trundle wheel during simulated match play. The players with the trundle wheel participated passively in the match by following one of the ten competing players. The distance measurements of the trundle wheel were used as reference values and compared to the Ubisense distance estimations. Best results were found with the measurements of a single mounted transponder on top of the athletes heads. No differences were detectable in the accuracy between measurements in the centre and at the borders of the basketball field. The (Ubisense) systems difference to the (trundle wheel) reference was 3.45 ± 1.99%, resulting in 95% limits of agreement of −0.46–7.35%. The study indicates the examined systems sufficient accuracy for time-motion analysis in basketball.