3-D BIOMECHANICAL ANALYSIS OF THE MOTOR PATTERNS OBSERVED DURING THE 10 M RIFLE-SHOOTING MODALITY

Abstract

INTRODUCTION Postural stability is an important characteristic of sport activities like shooting and archery. Athletes capacity to control quasi-static motor patterns has been considered as the most important factor to obtain high scores. The behavior of the shooter-rifle system emerges from the dynamic interactions of its parts. Thus the problem of postural control consists in the maintenance of a stable posture developing a series of neuromuscular actions (sinergies) to eliminate degrees of freedom in the joints. The main purpose of this study is to describe, by means of a few mechanical parameters, the small amplitude oscillations of the body segments that take place during aiming and evaluate their influence on the performance. During the experimental procedure an experienced shooter performed 60 shots (score 7.81+1'.38) with an air-rifle from the distance of 10 m. The kinematic and stabilometric data were registered using a measurement chain integrated by a SAC Sonic Digitizer (GP8-3D) and a strain-gauge force platform (DINASCAN-IBV) which is described elsewhere (Gianikellis et al., 1994). After data treatment ("smoothing" and differentiation procedures) the aiming time (last 5 sec) was divided in ten intervals of 500ms and stability parameters as the range of movement of body landmarks and segmentsmn or their standard deviation (precision error) were calculated in every interval (Zatsiorsky and Aktov, 1990). between scores obtained on the target and the stability parameters especially during 2- 1.5 s before the shot that correspond to the 7th time interval. During this rnterval the shooter was gradually started to press the trigger. Discriminant analysis of the data (canonical correlation coefficient = .056, pc ,0007) suggested that 84% of the good shots and 72% of the poor shots were classified correctly on five stability parameters. CONCLUSION For the described experimental conditions and aiming procedures the results of the present study confirm that the shooting quality (performance) depends strongly on the obtained stability parameters. REFERENCES Gianikellis, K.; et al. (1994). A measurement chain applicable in the Biomechanics of shooting Sports. In proceedings of the Xllth Symposium of I.S.B.S. Hungary, 266-269. Mason, B.R. et al., (1990). Factors Affecting accuracy in Pistol Shooting. Excel., 3, 2, 1-7. Zats~orsky, V.M. and Aktov, A.V. (1990). Biomechanics of highly precise movements : the aiming process in Air Rifle shooting. Journal of Biomechanics, 23, suppl. 1, 35-41. RESULTS The results of the statistical analysis of the data confirmed significant (pc .0004 - p< ,005) linear correlations (r = -.45 - r = -.35)