Validation of a motion model for soccer players' sprint by means of tracking data.

In soccer game analysis, the widespread availability of play-by-play and tracking data has made it possible to test mathematical models that have been discussed mainly theoretically. One of the essential models in soccer game analysis is a motion model that predicts the arrival point of a player in t s. Although many space evaluation and pass prediction methods rely on motion models, the validity of each has not been fully clarified. This study focuses on the motion model proposed by Fujimura and Sugihara (Fujimura-Sugihara model) under sprint conditions based on the equation of motion. A previous study indicated that the Fujimura-Sugihara model is ineffective for soccer games because it generates a circular arrival region. This study aims to examine the validity of the Fujimura-Sugihara model using soccer tracking data. Specifically, we quantitatively compare the arrival regions of players between the model and real data. We show that the boundary of the player's arrival region is circular rather than elliptical, which is consistent with the model. We also show that the initial speed dependence of the arrival region satisfies the solution of the model. Furthermore, we propose a method for estimating valid kinetic parameters in the model directly from tracking data and discuss the limitations of the model for soccer games based on the estimated parameters.

Space evaluation in football games via field weighting based on tracking data.

In football game analysis, space evaluation is an important issue because it is directly related to the quality of ball passing or player formations. Previous studies have primarily focused on a field division approach wherein a field is divided into dominant regions in which a certain player can arrive prior to any other players. However, the field division approach is oversimplified because all locations within a region are regarded as uniform herein. The objective of the current study is to propose a fundamental framework for space evaluation based on field weighting. In particular, we employed the motion model and calculated a minimum arrival time [Formula: see text] for each player to all locations on the football field. Our main contribution is that two variables [Formula: see text] and [Formula: see text] corresponding to the minimum arrival time for offense and defense teams are considered; using [Formula: see text] and [Formula: see text], new orthogonal variables [Formula: see text] and [Formula: see text] are defined. In particular, based on real datasets comprising of data from 45 football games of the J1 League in 2018, we provide a detailed characterization of [Formula: see text] and [Formula: see text] in terms of ball passing. By using our method, we found that [Formula: see text] and [Formula: see text] represent the degree of safety for a pass made to [Formula: see text] at t and degree of sparsity of [Formula: see text] at t, respectively; the success probability of passes could be well-fitted using a sigmoid function. Moreover, a new type of field division approach and evaluation of ball passing just before shots using real game data are discussed.

Construction of a soft wearable body cooling system for persons with spinal cord injury.

This paper describes the construction of a body cooling system to avoid heatstroke for survivors of cervical spinal cord injury. For accomplishment of this purpose, we chose the neck as a cooling point of the body, and we constructed a prototype neck cooling head with a refrigerated circulator. The neck cooling head was made by thin heat-welding thermoplastic films with high thermal conductivity. To test our proposed system, we conducted experiments on two unimpaired participants in a room which simulated a hot summer day (33 [°C], relative humidity 40%). Reduction of sweating were observed, and the average skin temperatures and the core temperature of the head with cooling increased more slowly than those without cooling. The estimated cooling power of the proposed system was about 10 [W] with 50 [W] total power consumption of the cooling head.

Characterization of the pierce two-node model under exercise load by parameter optimization toward construction of a modified thermal model for persons with spinal cord injury.

In this study, we attempted to develop a thermal model for estimating a body temperature in persons with spinal cord injury (SCI) during exercise. To clarify requisites for the SCI thermal model, we compared actual body temperature of SCI subjects with that calculated with a standard thermal model, that is, the Pierce two-node model. Model optimization by the parameter search method was able to fit the model-estimated skin and core temperature with those in able-bodied subjects during repeated exercise and rest. However, there remained a phase shift between actual and model-estimated core temperature trends in SCI subjects even after the optimization. The comparison of the optimized parameter combinations revealed that the Pierce two-node model was able to express loss of sweating in the SCI subjects, but unable to express delay in heat accumulation and dissipation. These results suggest that SCI thermal model requires additional nodes that express the speed and extent of heat transfer in the body of SCI persons.