Kerstin Witte

Applying a principal component analysis to movement coordination in sport

Because of the complexity of sports movements, biomechanical analyses contain many kinematical or dynamical parameters and characteristic curves. Principal component analysis (PCA) is a technique for simplifying a dataset by reducing multidimensional datasets to lower dimensions for analysis. The purpose of this article is the presentation of several studies which used the PCA to solve various problems in the movement science in sports. In particular, we interpret the number of the components or also named components with relatively high eigenvalues as the number of degrees of freedom. For cyclic and automated movements, the first PCA component is dominant. The PCA was successfully applied to gait analyses in rehabilitation and in triathlon as well as in riding. Phase plots could be used to quantify the variability of the movement coordination.

Comparing the effectiveness of karate and fitness training on cognitive functioning in older adults—A randomized controlled trial

Background Recent studies demonstrate a slowdown in deterioration of cognitive functioning in old age through aerobic training. There is evidence that the combination of aerobic, balance, and coordination exercises leads to an improvement or maintenance of cognitive functions. Such age-related exercises can especially be found in East Asian martial arts. The purpose of the current study is to verify whether karate training for older adults improves cognitive functioning and, if an improvement can be found, which cognitive fields are influenced. Methods Eighty-nine older women and men (mean age: 70 years) participated in this study. The participants were randomized into 2 intervention groups (karate group and fitness group, duration of intervention: 5 months) and a control group. All participants had to accomplish a cognitive test battery before and after the intervention. In a secondary study the karate group had an additional intervention for another 5 months. Results The results show that there is a significant improvement in motor reactivity, stress tolerance, and divided attention only after the 5-month karate training period. Additionally, the results of the secondary study indicate further improvements after 10 months. Conclusion The 5-month karate training can help to enhance attention, resilience, and motor reaction time, but a training period of 10 months is even more efficient.

Quantification of Golfer-club Interaction and Club-type’s Affect on Dynamic Balance during a Golf Swing

The current study aimed to provide a holistic picture of efficient golf swing and to determine the club contribution to weight shift patterns. Synchronized data from 3D motion capture (12 cameras, 250 Hz, VICON v8i) and ground reaction force (KISTLER platforms) were collected from 13 advanced golfers. The results showed that a) the club’s dynamic influence was closely related to wrist and elbow control, which determined the degree of separation between centre-of-ground-reaction-force and centre-of-gravity of a golfer; b) a Driver has more influence on a golfer’s weight transfer than an Iron; c) Club head speed is related to the coordination between shoulder and hip joint; and d) the ball release velocity is influenced by wrists “uncock” (a combination of hand extension and ulnar abduction for accelerating the club to its maximum velocity) at ball contact. Via the novel protocol that customizes to subjects’ individual anthropometrical data and separates the body-club system, the current study presents both individual contributing components and more insight view on subjects’ golf swing using different clubs.

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.

Analysis of anticipation by 3D motion capturing – a new method presented in karate kumite

ABSTRACT Anticipation is an important performance factor in karate kumite. A new approach analysing anticipation in realistic combat situations by motion capturing with a high temporal resolution is presented. The advantage of this approach is that both karate athletes interacting sports specific can be recorded synchronously; thus, the presented method has the potential to analyse visual information pickup due to coordination pattern of interaction between real athletes. The aim is to demonstrate the usability of the current method for anticipation research and to investigate if the distance between two athletes and their attacking technique play a role in the reaction of the defending athlete. Furthermore, relevant cues lying within each attacking technique and little individual differences are shown. Four male karate athletes took part in this study. Logistic regression indicated that both factors (distance × attacking technique) play a significant role in reaction. However, a correlation between these factors shows that only the attacking technique is a good predictor for reaction. Results show that the attacking technique jabbing punch (jap. Kizami-Zuki) was easier to anticipate than the attacking techniques reverse punch (jap. Gyaku-Zuki) and the round kick (jap. Mawashi-Geri).

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.

Approach of a Model for the Interaction Between Athlete, Sports Equipment and Environment

For the interaction between athlete, sports equipment and environment there are general characteristics which are important to consider during the product design process of performance oriented sports equipment. The aim of this study is to describe these aspects of the athlete-sports equipment-system and to get a model for the interaction between athlete, equipment and environment. The model comprises the athlete himself, his activities, the sports equipment and environment. Furthermore the subjective criteria in the model, perception, emotion, status symbol and trend-setting, are of interest. Some examples will illustrate the model. This approach can be used to assist the designer of performance oriented sports equipment and thus to support a systematic product design process in sports.

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.

KaraKter: An autonomously interacting Karate Kumite character for VR-based training and research

Abstract We report on the creation of an autonomous Karate Kumite character (KaraKter) that can be used for VR based training and research in Karate Kumite. For the real time interaction with KaraKter, a human athlete is tracked in a virtual environment. KaraKter moves in Karate specific ways, approaches the athlete and realizes adequate attacks depending on the behavior of the human. KaraKter passed tests on functionality and performance and has been evaluated by high ranking Karate experts. The evaluation showed that the athletes accept KaraKter as an actual opponent. All experts rated the system to be useful in the training of Karate Kumite.