FIELD TRIAL OF THE LAVEG LASER DIODE SYSTEM FOR KINEMATIC ANALYSIS IN VARIOUS KINDS OF SPORTS

Abstract

The newly developed LAVEG laser diode system (LAser VElocity GuardJENOPTLK Technologie GmbH Jena) opens up new prospects of kinematic analysis of one-dimensional acceleration phases in various kinds of sport/events. So the distance-time- and velocity-time-functions which may be of interest as well as individual kinematic parameters of a motion are recorded in ON-LINE mode and available to trainer and sportsman as instant (real-time) information. Contrary to ultra sound techniques it is not necessary to carry along a transmitter/receiver attached to the sportsman/device. Consequently, the whole complexity and expense of the measuring equipment is considerably reduced in comparison with video or film analysis techniques. The measurement principle is based on travel-time measurements of laser pulses (wavelength 904 nm, pulse duration 20 ns, beam divergence 3 mrad) transmitted by a semiconductor laser diode. The laser beam is diffusely reflected at the sportsman/device without using a reflector and then registered by a laser detecting diode inside the LAVEG. The kinematic functions are computed by means of a microcontroller on the basis of individual distance measurements executed with quartz-stabilized counter timing. A sample rate of 50 Hz enables to cover a movement pattern of 30 s duration up to a distance of 200 m in all velocity ranges occurring in sports. Comparative measurements performed in luge sport during the start phase using the system described in this article and the high precision pulse light photogrammetry (GUTEWORT 1978) have revealed a high degree of correspondence of both techniques. Thus, in both measurement techniques the value of the first maximum of the horizontal velocity resulting from the accelerative impact on both sides during the start phase (so called "penguin") IS characterized by a statistically secured identity with a level of significance of < 0. 01 based on (n = 3 1 ). As regards speed measurements, the accuracy of the technique can be indicated with 0.1 mls in the range up to 10 m/s. It is a specific advantage of the system that this measurement accuracy does not depend on the distance between measurement object and measurement device. Up to the moment the system has been applied to advantage for analyzing the start and acceleration phases in athletics as well as in luge and bobsled sports. Within athletics the system was used in sprint as well as for analyzing long jump and triple jump approach phases. In bobsled races the acceleration of the bob was measured on the start-push track considering some aspects of a profound performance diagnosis. LAVEG measurements carried out on specific start-simulation devices proved to be especially useful in luge sport. As a result, the velocity time-functions are available immediately after a training exercise has been finished which facilitates a differentiated evaluation of individual technical performance of movement and the effect of training loads acting upon the locomotor system of a sportsman.