Variability Of Selected Kinematic Indicators In The Shot Put As The Effect Of Technique

University of Physical Education in Warsaw, Poland.

Introduction and aim

Throwing events in track and field (shot put, hammer throw, javelin throw and discus throw) have been the subject of a number of studies (Ariel, 1979; Bartonietz, 1996; Lanka, 2000; Marhold, 1973). Good performance in mentioned track and field competitions are mainly determined by the athete's technique than the tactics. The most popular method in analysing technique, especially during competitions (but also during training sessions) has been video motion analysis (qualitative and quantitative). The complex movements like shot put or discus throw require multidimensional analysis. Spin and glide are the main techniques used by athletes during shot put performances. Especially the spin shot put technique is an extremely complex movement, which requires a high level of motor control, biomotor abilities and an optimal constitution of the thrower (Čoh & Jošt, 2005). The aim of this study was to compare the glide and spin shot put techniques, at the last phase of the throw, by calculating absolute error of selected biomechanical parameters using MVN Analyze system.

Patients/materials

Eight world-class, right-handed shot putters (mean ± SD: age = 25 ±1 years, body height = 1,92 ± 0,07 m, body mass = 112,4 ±9,1 kg) participated in the study. Three of them used spin technique, whereas the others used glide technique.

Methods

In this case, full body inertial sensing data from the MVN Biomech system was combined with 2 synchronized camera video streams. All measurements were performed on the Jozef Piłsudski University of Physical Education stadium.

Following kinematic indicators of the athlete (CG – athlete's center of gravity in case of velocities) during release (RLS - the last contact of the athlete's) were taken into account during analysis including only measured trials:

• Height of release (H) - the height of the center of the hand above the surface of the circle at release.
• Height of the center of the body during release (h) - the height of the center of body mass above the surface of the circle at the moment of release.
• Resultant velocity (Vw) of the athlete's center of gravity (CG)
• Horizontal velocity (Vx) of the athlete's center of gravity (CG)
• Vertical velocity (Vy) of the athlete's center of gravity (CG)
• Shoulder-hip separation (S-H) during RLS. S-H is the orientation of the hips relative to the shoulders. A neutral position (0˚separation) occurs when the shoulders and hips are aligned with one another. A positive angle occurs when the throwing side shoulder is posterior to the throwing side hip.
• Rear (right) and front (left) knee angle (β_p and β_l, respectively) - relative angle between thigh and leg segments.
• Shoulder and elbow angle of the right (throwing) arm (φ_p and δ_l, respectively).
• Right and left hip angle (λ_p and λ_l, respectively).

Results

According to the mean values (table 1), the angle indicators like: right knee angle (β_p), left hip angle (λ_l) lateral and resultant path of the athlete's center of gravity, differed more in spin technique than in glide one.

Table 1. Average values (±SD) for the release and the distance in horizontal, vertical lateral direction and resultant distance of the athletes center of gravity (CG) according to the technique (S-spin and G-glide).

The greatest differences were found for the S-H in both techniques. The rest of the indicators of the athlete's and the put (due to the AV) had the small value (below 10% - table 2).

Table 2. Average percentage values of the average relative error (AV) for the distance and the angle indicators of the athlete's with the division into spin (S) and glide (G) technique.

Discussion and conclusions

Although the spin and glide techniques were different in utilizing the way of acceleration of the shot (angular and linear properly), the absolute errors of selected parameters, at the moment of release, were very similar in both techniques. Average values of absolute errors during release: β_p, φ_p, λ_p, λ_l, S-H turned out to be slightly more stable for the glide technique.

Acknowledgment: The work financed from budgetary resources on science in the years 2011-2014 by the Polish Ministry of Science and Higher Education – grant no N RSA1 002251

References

[1] Ariel G. Biomechanical analysis of shot putting. Track and Field Quarterly, Review, 1979; 79: 27-37.
[2] Bartonietz K. Biomechanical aspects of the performance structure in throwing events. Modern Athlete and Coach, 1996; 34 (2): 7-11.
[3] Lanka J. Shot putting. In Biomechanics in Sport (eds. Zatsiorsky V.M.), 435-457; 2000.
[4] Marhold G. Biomechanical analysis of the shot put. Nelson WRC and Morehouse CA (eds.), Biomechanics IV, Baltimore: University Park Press, 502-509; 1973.
[5] Čoh M., Jošt B. A kinematic model of rotational shot-put 23 International Symposium in Biomechanics in Sports Beijing, China, 2005: 357-360.