Automatic Registration of Footsteps in Contact Regions for Reactive Agility Training in Sports.

In collective sports, reactive agility training methodologies allow to evaluate and improve the player performance, being able to consider a mixture of technical, tactical, physical, and psychological abilities, similarly to real game-play situations. In this article, we present a new methodology for reactive agility training (neural training), the technological setup for the methodology, and a new footstep tracking algorithm, as the key element for automating the speed data gathering process, necessary for obtaining the relevant variables of the neural training approach. This new methodology is oriented to accurately measure two of the most relevant variables for reactive agility training: total response time (sprint time) and response correctness, related to a stimuli sequence presented to a player. The stimuli were designed to properly represent realistic competitive conditions for player training, contextualized to soccer. In order to automate the gathering process, a new computer vision based automatic footstep detection algorithm has been integrated to the system. The algorithm combines Kalman Filters, segmentation techniques, and perspective geometry, for obtaining highly precise detections of the moment a relevant footstep occurs in real-time, reaching a precision higher than 97%. Plus, the algorithm does not require any special marker, invasive sensor, or clothing constraint on the player.

Anthropometric characteristics of elite rhythmic gymnasts / Características antropométricas de gimnastas rítmicas de elite

The main aim of this study was to identify the morphological characteristics, to determine the tendency in the physical structure, differences and similarities according to categories based on age of the Chilean team of Rhythmic Gymnastics. We performed an anthropometric analysis of 60 gymnasts, fractioned by categories: preschoolers and schoolers (n= 11), junior (n= 28) and senior (n= 21). The anthropometric analysis was determined based on the study of the body composition, through pentacompartimental fractionation method (Kerr), somatotype (Heath & Carter) and the body mass index (Quetelet). The results showed significant differences between preschoolers and schoolers and higher categories (junior and senior) in the general anthropometric variables of body mass, height and BMI. Regarding the body composition, we only found significant differences in the percentage of muscle mass between the preschoolers and schoolers when being compared with the other two categories. In the study of somatotype, the prevalence of ectomorphic categorization was only found in the preschoolers and schoolers (meso-ectomorph), while in the junior category a mesomorph-ectomorph somatotype was observed and a central type in the senior category. We conclude that the morphology of the selected Chilean Rhythmic gymnastics depends on the category, as observed in the anthropometric characteristics related to the body composition and somatotype. Therefore, this factor is not useful in establishing a clearer tendency in the morph structure for this sport at a national level.

El objetivo principal de este estudio fue identificar las características morfológicas para determinar la tendencia de la estructura física, las diferencias y similitudes de acuerdo con las categorías basadas en la edad de la Selección Chilena de Gimnasia Rítmica. Se realizó un análisis antropométrico de 60 gimnastas, fraccionado por categorías: preescolares y escolares (n = 11), junior (n = 28) y senior (n = 21). El análisis antropométrico se determinó en base al estudio de la composición corporal, a través del método de fraccionamiento pentacompartimental (Kerr), del somatotipo (Heath & Carter) y el índice de masa corporal (Quetelet). Los resultados mostraron diferencias significativas entre los niños preescolares y escolares y las categorías superiores (junior y senior) en las variables antropométricas generales de masa corporal, altura e IMC. En cuanto a la composición corporal, sólo encontramos diferencias significativas en el porcentaje de masa muscular entre los preescolares y escolares, cuando se comparan con las otras dos categorías. En el estudio del somatotipo, la prevalencia de la categorización ectomórfica solamente se encontró en los niños preescolares y escolares (meso-ectomorfo), mientras que en la categoría junior se observó un somatotipo mesomorfo-ectomorfo y un tipo central en la categoría senior. En conclusión, la morfología de los seleccionados de gimnasia rítmica chilena depende de la categoría, como se observa en las características antropométricas, relacionados con la composición corporal y el somatotipo. Por lo tanto, este factor no es útil para establecer una tendencia clara en la estructura morfológica para este deporte a nivel nacional.

Middle and long distance athletics races viewed from the perspective of complexity.

Middle and long distance athletics races behave as power-laws when time (or average speed) and distance are related, thus suggesting the presence of critical phenomena. Power-laws as a function of the athlete's position in the all-time world ranking allows us to define a Performance Index that reveals the existence of possible multifractal structures associated to the natural barriers to that the athletes tend in their evolution towards better results and in pursuit of world records. The new theories of self-organized critical phenomena provide an explanation for the power-law and fractal structures in systems at, or near, their critical points. In this paper we analyse the athletic races using these theories and as a result of this study a new variety of interpretations are posited.