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

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

A PROCEDLIRE FOR DETERMINING TWO 'POSTURAL INSTABILITY' FACTORS THAT INFLUENCE ON THE PERFORMANCE IN RIFLE-SHOOTING

The purpose of this study is to analyze the individual rifle-shooting sport technique of an international level shooter defining the factors of mechanical instability that have negative effects on the performance. Kinematic and stabilometric data were registered by means of a sonic digitiser synchronised with a force platform. Postural stability has been evaluated for ten intervals of the last five seconds of the aiming time. Multivariate analysis techniques allowed to identify two factors of 'postural instability' that explain the 78.8% of the total variability. Namely, 'instability of the segment pelvis during the 7th interval of the aiming time' and 'instability of the structure that form the rifle and the supporting it upper trunk during the final second of the aiming line'. The results provide objective information respect to the motor patterns in the rifle-shooting justifying the proposed theoretical model for the identification of the postural stability and its influence on the performance

A MEASUREMENT CHAIN APPLICABLE IN THE BIOMECHANICS OF SHOOTING SPORTS

SONIC DIGITIZING is a new and very precise method for kinematic analysis In shooting sports (Gianikellis et al. 1992). The purpose of this study was to Improve the technical characteristics and capabilities of this method, also its applicability for complete Biomechanical Analysis in movements of high precision and shooting sports Now, the sampling rate 1s 66 6 Hz (Instead of the 37 Hz previously obtained frequency) divided by the number of emitters placed in an active volume of a cube with two meters side length. The Sonic Digitizer would be optionally faster working In smaller volumes (up to 100 Hz) In this way, we can use more ultrasound emitters sampling them within an appropriate rate for this class of motor patterns (according to Shannon s theorem). Also, the 3-d~mens~onaclo ordinates of the emitters are calculated respect to the system of reference by means of a Newton-Raphson's optimization algorithm This algorithm improves the precision of the system The calculated standard deviation for the coordinates X, Y, Z 1s 0 1 mm (Instead of the 0.15 mm previously calculated standard deviation). Since sonic digitizer is a multiplexing system, we have implemented an interpolation and smoothing of data algorithm to have simultaneously the coordinates of all anatomical points of Interest. This algorithm 1s based on the Natural B-Spline functions according to the True Predicted Mean-Squared Error criterion (Woltring 1986) After this, we can easily obtain the velocities and accelerations of the anatomical markers of interest Finally, the measurement chain is completed with a strain-gauge Force Platform (DINASCAN) synchronized with the Sonic Digitizer. In this way, there IS the possibility to carry out stabilometric studies treating the variability of the coordinates of the Centre of Pressure during the aiming process. The resultant parameters of the kinematic and stabilometric analysis are referred to a common temporal base up to the Instant of the triggering which IS detected by means of a microphone senso

A STRAIN-GAUGE UNIAXIAL LOAD CELL TO EVALUATE MUSCULAR STRENGTH LEVEL IN ISOMETRIC EXERCISE

INTRODUCTION "Muscle strength is defined as the magnitude of the torque exerted by a muscle (or muscles) in a single maximal isometric contraction of unrestricted duration" (Atha, 1981 ). Strength diagnosis (Schmidtbleicher, 1992) by means of strength and power tests is considered as a very useful procedure to identify talents or to control the evolution in the tralning or rehabilitation progress. The results of specific tests provide information about relative deficiencies and they can be used to figure out individual strength training programs. Also, maximum isometric force and the rate of force development seem to be important qualities related to the athletic performance (Wilson and Murphy, 1995). In consequence of this study a strain-gauge uniaxial load cell has been designed and developed to measure in real-time, and store the well established mechanical parameters to evaluate muscular force during isometric exercise. These parameters are: a) the peak value of the force exerted on the load b)the time to reach a predetermined percentage of its maximum value c) the gradient of the force-time curve d) the interval to maintain a determined level of isometric force. The measurement chain includes: i) the load cell which is an lnstrumentated steel ring with a Wheatstone circuit ii) the amplifier iii) a low-pass analogic filter iv) an AID converter v) the personal computer with mathematical processor and the software for signal treatment and results' representation. RESULTS An INSTRON electro-hydraulic testing system has been used to calibrate the measurement chain and to evaluate its performance (r = -.999, pc ,00000). The measurement range of the load cell is up to 3500 N, its precision is k5 N and its sampling rate is 500 Hz. The software permits the representation of the results in real-time providing the possibility for feedback applications. CONCLUSION Convenient technical characteristics recommend the use of this uniaxial load cell to evaluate muscle strength capacity in isometric conditions.. REFERENCES Atha, J. (t981). Strengthening muscle. In D.I. Miller (Ed.) Exercise and Sport Science Reviews, vol. 9, 1-73. Philadelphia Franklin Institute. Shmidtbleicher, D. (1 992). Training for Power events, Strength and Power in Sport. P.V. Komi (Ed.), 381-395, Blackwell. Wilson, G. J.; Murphy A.J. (1 995). Strength Diagnosis: the use of the pre-training test data to determine individual specific strength training. XVth I.S.B. Congress. Book of abstracts, 994-995

Clinical phenotypes of acute heart failure based on signs and symptoms of perfusion and congestion at emergency department presentation and their relationship with patient management and outcomes

Objective To compare the clinical characteristics and outcomes of patients with acute heart failure (AHF) according to clinical profiles based on congestion and perfusion determined in the emergency department (ED). Methods and results Overall, 11 261 unselected AHF patients from 41 Spanish EDs were classified according to perfusion (normoperfusion = warm; hypoperfusion = cold) and congestion (not = dry; yes = wet). Baseline and decompensation characteristics were recorded as were the main wards to which patients were admitted. The primary outcome was 1-year all-cause mortality; secondary outcomes were need for hospitalisation during the index AHF event, in-hospital all-cause mortality, prolonged hospitalisation, 7-day post-discharge ED revisit for AHF and 30-day post-discharge rehospitalisation for AHF. A total of 8558 patients (76.0%) were warm+ wet, 1929 (17.1%) cold+ wet, 675 (6.0%) warm+ dry, and 99 (0.9%) cold+ dry; hypoperfused (cold) patients were more frequently admitted to intensive care units and geriatrics departments, and warm+ wet patients were discharged home without admission. The four phenotypes differed in most of the baseline and decompensation characteristics. The 1-year mortality was 30.8%, and compared to warm+ dry, the adjusted hazard ratios were significantly increased for cold+ wet (1.660; 95% confidence interval 1.400-1.968) and cold+ dry (1.672; 95% confidence interval 1.189-2.351). Hypoperfused (cold) phenotypes also showed higher rates of index episode hospitalisation and in-hospital mortality, while congestive (wet) phenotypes had a higher risk of prolonged hospitalisation but decreased risk of rehospitalisation. No differences were observed among phenotypes in ED revisit risk. Conclusions Bedside clinical evaluation of congestion and perfusion of AHF patients upon ED arrival and classification according to phenotypic profiles proposed by the latest European Society of Cardiology guidelines provide useful complementary information and help to rapidly predict patient outcomes shortly after ED patient arrival

SONIC DIGITIZING: a new method for Kinematic Analysis in sports and movements of high precision - Air rifle Shooting

In Shooting sports, according to Coaches opinion, body segments stabilization is considered as the most important factor which influences the performance of the athletes. Many researchers have used different instrumentation (Accelerometers, Force plates, Selspot system etc), to relate the performance with concrete Biomechanical parameters. As far as we know, none of the up to now proposed methods describes the 3dimensional Kinematics of Shooting sports techniques during the aiming process. It seems to be very interesting to become acquainted with the oscillations of the links of the kinematic chain, provided that from a mechanical pint of view, the Shooter and the rifle form an oscillating system around a static position and according to an important principle of General Systems Theory the behavior of a system emerges from the dynamic interactions of its parts. In the Institute of Biomechanics of Valencia, we have developed a new method, based on the use of ultrasounds, suitable for the description of the shooter-gun system geometry before and during the shot. The Sonic Digitizing system consists of the GP8-3D Sonic Digitizer which includes 16 sound emitters fixed on the shooter's body segments and on the barrel of the rifle, 4 microphone\sensors, the Multiplexer unit and the Control unit which communicates with the personal computer via a Parallel Interface Card (PIO 12). The sampling rate is 37 Hz divided by the number of emitters in an active volume of 2 meter side cube. This sampling rate seems to be enough for our study according to Shannon's theorem. The nominal resolution of the system is 0.1 mm and the calculated standard deviation is 0.15 mm. The system works emitting impulses of ultrasounds generated at the tip of every emitter. Cognizant of the speed of the sound in still air (343.8 m I sec, 20°C) and the time required for the sound to reach the microphones, the I program calculates, in REAL-TIME, the coordinates X, Y, Z respect to our reference system. In addition to the possibility of a complete Kinematic analysis, we can establish a real-time feedback loop, providing the shooter with a continuous auditory signal as function of the desviation of the aiming line, that define two emitters fixed on the gun, from the center of target. At last, but not at least, we can record simultaneously the displacement of the center of pressure on the force plate which complete our measurement setup