A biomechanical comparison of the rotational and glide techniques in the shot put

Aim: In shot put competitions are commonly used the rotational (ROT) or glide (GL) techniques. Previous studies have compared the two styles with a cross-sectional approach, analyzing only one type of technique for each athlete, with the drawback that the characteristics of athletes may be confounding factors. Therefore, this study aimed to compare the biomechanical parameters of ROT and GL in national level shot putters able to correctly execute both the techniques. Methods: The Smart-DX (BTS Engineering, Milano) was used to collect and analyse the 3d data. The experimental set-up included a set of nine 250-Hz cameras and two force plates (Kistler 9286AA, Switzerland). Four high-level Italian shot putters were involved (2 males, 2 females). For each athlete 6 throws (3 ROT and 3 GL) were measured, acquired and for the analysis divided in 4 phases: T1 (first movement), T2 (flight phase), T3 (double support) and T4 (push-throw). Results: Some angles (right knee, hip/throwing direction) and execution times showed significant differences between the techniques mostly in T1, T2 and T3; the trunk incline, the distance between heels (higher in the GL) and the shot velocity showed differences in all phases. Indeed, the shot velocity had a gradual increase in GL, while in ROT it had an abrupt increase in T4. The mean distance thrown was higher when using GL in male, while it was similar for the two styles in female. The distance thrown was related, in both the techniques and genders, to many biomechanical indices, including the hip rotation, the distance between heels, the shot height and, especially in females (r = 0.88), to the velocity at release. Male putters showed a higher shot velocity than female in all phases of GL, but only in T4 of ROT. In males, the peak vertical GRF at the planting point was positively related to the distance thrown in GL and in ROT (r = 0.55 and r = 0.58, respectively), while in females only in GL (r = 0.67). Conclusion: The examined techniques showed different biomechanical characteristics in T1, T2 and T3, while T4 was rather similar. The main difference between genders was represented by the higher peak vertical GRF shown by male athletes at the planting phase, demonstrating that these athletes rely on the force expressed by the pointing leg. On the contrary, females count more on accelerating the shot as much as possible. The present findings, although at a preliminary stage, provide a framework for coaches to analyse the performance of their athletes and to examine which technique may be the best according to the individual characteristics. References Gutie\ub4rrez-Davila M, Rojas J, Campos J, Ga\ub4mez J, Encarnacio\ub4n A (2009) Biomechanical analysis of the shot put at the 12th IAAF world indoor championships. New Stud Athlet 24(3):45\u201361 Stepanek J (1987) Comparison of the glide and the rotation technique in the shot put. Biomechanics in sports: proceedings of the 5th ISBS symposium, pp 135\u201314