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Nicolas Olivier and Frédéric N. Daussin

Abstract

Swimming and throwing are involved in water-polo player performance. These movements have a common biomechanical basis in the use of the internal shoulder rotation and adductor muscles. The aim of the study was to evaluate the relationship between shoulder isokinetic evaluation and throwing velocity as well as swimming performance in female water-polo players. Fifteen high level water-polo players completed two isokinetic shoulder evaluations to determine peak torque of shoulder rotators of the dominant shoulder (concentric and eccentric movements at an angular velocity of 60°·s-1 and concentric movements at an angular velocity of 240°·s-1) and shoulder extensors of both arms (concentric movements at an angular velocity of 60°·s-1 and 240°·s-1). Throwing velocity was measured using a radar gun placed 5 m behind the goal post. Front crawl swimming velocity was determined at 25 m, 100 m and 400 m distances. Concentric peak torque at 60°·s-1 and 240°·s-1 of internal rotators and eccentric peak torque at 60°·s-1 of external rotators were predictors of throwing velocity. The best model to explain the relationship between isokinetic evaluations and throwing velocity was obtained with concentric IR peak torque at 60°·s-1 and eccentric ER peak torque at 60°·s-1 (r2 = 0.52, p = 0.012). Relative total work done and peak torque of shoulder extensors were predictors of 25 m swimming velocity. Shoulder isokinetic evaluations correlate significantly with swimming performance and throwing velocity of female water-polo players. The results may help coaches to develop new strategies such as eccentric dry land training programs to increase both shoulder external rotators strength and throwing velocity.

Open access

Olivier Bodini, Antoine Genitrini and Nicolas Rolin

Abstract

Since the last two decades huge systems (such as giant graphs, big data structures, . . . ) have played a central role in computer science, and with the technology improvements, those large objects are now massively used in practice. In order to handle them we need to analyse some typical properties of models of large objects. One way to study typical behaviours consists in generating random objects to get some experimental results on their properties. A new technique has been introduced ten years ago: the Boltzmann sampling. It has been presented by Duchon et al, and is based on automatic interpretation in terms of samplers of the specification of the combinatorial objects under study.

One of the core problem in Boltzmann sampling lies in the distribution of the object sizes, and the choice of some parameters in order to get the more appropriate size distribution. From this choice depends the efficiency of the sampling. Moreover some additional ideas allows to improve the efficiency, one of them is based on some anticipated rejections, the other one on the combinatorial differentiation of the specification. Anticipated rejection consists during the recursive building of a random object to kill the process as soon as we are sure to exceed the maximum target size, rather than waiting until the natural end of the process. In the original paper, while both approaches have been presented, and used on the same kind of structures, the methods are not compared. We propose in this paper a detailed comparison of both approaches, in order to understand precisely which method is the more efficient.