Nico Ganter

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.

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.

Application of Different Computerized Methods for Modelling the Training-Performance Relationship

In the recent past, computer aided simulative models have been utilised to analyse the interaction of load and performance in training. The aim of the study was the evaluation of two models with antagonistic structure, the fitness-fatigue model and the PerPot model. Both were applied on an empirical dataset, containing training and performance data of ten sport students during an eight week cycling training period. The modelling was conducted using appropriate software tools. Results showed interindividually different qualities in fitting of modelled and empirical performances. Since the fitness-fatigue model resulted in marginal model parameters, interpretation remained questionable. The PerPot model offered reasonable delay values but due to different performance levels, interindividual comparison was difficult. For modelling the training-performance relationship both models revealed specific characteristics with some limitations in the interpretation of the model parameters.

Measurement of Draw-Length Alterations in the Final Pull in Archery

In aiming it is important that an archer’s draw-length is quite constant and that the clicker position is only a few millimeters behind the tip of the arrow. At the end of the aiming phase the archer pulls back the arrow a little bit before he releases the shot. This is called the final pull. (1993) measured the alteration of the draw-length indirectly using an electromechanical device that was fixed to the grip and to the lower limb of the bow, but it is very time-consuming and complex to affix this electromechanical device to a bow. The aim of this paper was to describe a system developed to measure the draw-length in the final pull that is easy to handle and to research the final pull in highly skilled archers. The alteration of the draw-length was measured by acquiring the bending of the clicker using a strain gage that is fixed to the clicker: The clicker position during aiming is only a few millimeters behind the tip of the arrowhead. Therefore each alteration of the draw-length leads to an alteration of the bending line of the clicker because of the shape of the arrowhead. Seven archers (two male, five fe-male), all participants at the Junior World Championships and German National Championships performed 66 shots at 30m indoors. Each archer shot with his own personal bow, and the alterations of the draw-length in the final pull were acquired. The results suggest that irregularities in the final pull, especially the so-called “shrinking”, have a negative influence on the archers’ score.