Physiological and mechanical loads in Portuguese sub-elite football refereeing – a preliminary study

Este estudio tuvo como objetivo examinar la variación de la carga fisiológica y mecánica en un equipo arbitral de sub-élite, considerando las diferentes partes del partido y su rol (árbitro de campo vs árbitro asistente). Un árbitro de campo (32.57 años) y dos árbitros asistentes (31.05 años) fueron monitoreados durante cuatro juegos del Campeonato de Portugal a lo largo de la temporada 2018-2019 (categoría de edad senior, o adulto), utilizando ZephyrTM BioHarness. Se consideraron para el análisis las siguientes variables: temperatura cutánea, frecuencia respiratoria, frecuencia cardíaca (FC), porcentaje de frecuencia cardíaca máximo (%FCmáx), postura, actividad y pico de aceleración (ACpico). También se calculó la carga de impulso, expresada en N ∙ s. No se observaron diferencias fisiológicas y mecánicas según la parte del juego, considerando a todos los miembros del equipo arbitral. Se verificaron diferencias significativas entre los árbitros de campo y los árbitros asistentes en la primera y segunda parte y para el total de partido: en promedio, el árbitro de campo mostró valores superiores para temperatura cutánea (p = 0.016; r = -0.759), FC (p = 0.017; r = -0.757), %FCmáx (p = 0.017; r = -0,757), actividad (p = 0,017; r = -0,757) y ACpico (p = 0,017; r = -0,757). Curiosamente, no se encontraron diferencias para la carga de impulso entre el árbitro de campo y los árbitros asistentes. El perfil de actividad del árbitro de fútbol es fisiológica y mecánicamente exigente, incluso en un nivel de sub-élite. Las diferencias entre el árbitro de campo y los asistentes deben ser consideradas nel dibujo de programas de entrenamiento de preparación y acondicionamiento de árbitros para hacer frente a las demandas físicas de un partido de fútbol. This study aimed to examine the variation in physiological and mechanical load in a sub-elite refereeing team, considering the different parts of the match and their role (field referee vs assistant referees). One field referee (32.57 years) and two assistant referees (31.05 years) were monitored during 4 matches of the Portuguese Championship throughout the 2018-2019 season (senior age category, or adult), using the ZephyrTM BioHarness. The following variables were considered for analysis: skin temperature, respiratory rate (RR), heart rate (HR), percentage of maximum heart rate (%HRmax), posture, activity, and peak acceleration (ACCpeak). The impulse load, expressed as , was also calculated. No physiological and mechanical differences were observed according to match half, considering the refereeing team members. Significant differences were verified between field referee and assistant referees in the 1st half and the 2nd half and for total match-play: on average, the field referee had higher values for skin temperature (p = 0.016; r = -0.759), HR (p = 0.017; r = -0.757), %HRmax (p = 0.017; r = -0.757), activity (p = 0.017; r = -0.757), and ACCpeak (p = 0.017; r = -0.757). Curiously, no differences were found for impulse load between the field referee and the assistant referees. The football referee’s activity profile is both physiologically and mechanically demanding, even at a sub-elite level. Differences between field referee and assistants must be considered in refereeing fitness and conditioning training programs to cope with physical demands of a football match. Este estudo teve como objetivo examinar a variação da carga fisiológica e mecânica numa equipa de arbitragem sub-elite, considerando as diferentes partes da partida e o seu papel (árbitro de campo vs árbitro assistente). Um árbitro de campo (32.57 anos) e dois árbitros assistentes (31.05 anos) foram monitorizados durante quatro jogos do Campeonato de Portugal ao longo da época 2018-2019 (escalão etário sénior, ou adulto), utilizando o ZephyrTM BioHarness. As seguintes variáveis foram consideradas para análise: temperatura cutânea, frequência respiratória (FR), frequência cardíaca (FC), percentagem da frequência cardíaca máxima (%FCmáx), postura, atividade e pico de aceleração (ACpico). A carga de impulso, expressa em N ∙ s, também foi calculada. Não foram observadas diferenças fisiológicas e mecânicas de acordo com a parte do jogo, considerando todos os membros da equipa de arbitragem. Diferenças significativas foram verificadas entre o árbitro de campo e os árbitros assistentes na 1ª e na 2ª parte e para o total do jogo: em média, o árbitro de campo apresentou valores superiores para a temperatura cutânea (p = 0.016; r = -0.759), FC (p = 0.017; r = -0.757), %FCmáx (p = 0.017; r = -0.757), atividade (p = 0.017; r = -0.757) e ACpico (p = 0.017; r = -0.757). Curiosamente, não foram encontradas diferenças para a carga de impulso entre o árbitro de campo e os árbitros assistentes. O perfil de atividade do árbitro de futebol é fisiológica e mecanicamente exigente, mesmo a um nível de sub-elite. As diferenças entre o árbitro de campo e os assistentes devem ser consideradas na preparação da arbitragem e nos programas de treino e condição física para melhor lidar com as exigências físicas de um jogo de futebol.

Dynamic Stability of Sandwich Beams/Wide Plates Subjected to Axial Impulsive Loads

This paper presents an analysis for the dynamic stability of sandwich beams/wide plates subjected to axial impulsive loads. The formulation and solution of the problem is done by use of the extended high-order sandwich panel theory (EHSAPT). With the initial geometric imperfection included, the equations of motion in terms of seven generalized displacements are derived. The dynamic response of sandwich panels subjected to three different types of impulsive loads, namely, step, linear decay, and triangular impulse, is studied. Furthermore, the effects of the oscillation mode number, face/core materials, and geometries are investigated. It is observed that all measurements of the dynamic response, such as the maximum displacements, strains, and stresses, change at the same rate as the change of the impulse load magnitude and duration, for a specific impulse load profile. When the impulse load is lower than the static buckling load, the dynamic response is bounded no matter how long the load is applied. A step impulsive axial load with magnitude lower than the static buckling load can lead a sandwich panel to have a dynamic response as high as twice the static response. When the impulse load is higher than the static critical load, the dynamic response is unbounded with increasing load duration. However, it is possible that the dynamic response can be controlled at a low level if the duration of the impulse load is short enough, and thus, in this case, the load can safely exceed the static critical load.

External, Internal, and Perceived Training Loads and Their Relationships in Youth Basketball Players Across Different Positions

Purpose: To quantify external, internal, and perceived training loads and their relationships in youth basketball players across different playing positions. Methods: Fourteen regional-level youth male players (age: 15.2 [0.3] y) were monitored during team-based training sessions across 10 in-season weeks. The players were monitored with BioHarness-3 devices, to measure external (Impulse Load, in Newtons per second) and internal (summated-heart-rate zones [SHRZ], in arbitrary units [AU]) loads, and with the session rating of perceived exertion (sRPE, in AU) method to quantify perceived training load. Multiple linear mixed models were performed to compare training loads between playing positions (backcourt and frontcourt). Repeated-measures correlations were performed to assess the relationships between the load models, for all players and within playing positions. Results: External load (backcourt: 13,599 [2260] N·s; frontcourt: 14,934 [2173] N·s) and sRPE (backcourt: 345 [132] AU; frontcourt: 505 [158] AU) were higher in the frontcourt (P < .05, effect size: moderate), while SHRZ was similar between positions (backcourt: 239 [45] AU; frontcourt: 247 [43] AU) (P > .05; effect size: trivial). The correlations were as follows: large between the external load and SHRZ (r = .57, P < .001), moderate between SHRZ and sRPE (r = .45, P < .001), and small between the external load and sRPE (r = .26, P = .02). The correlation magnitudes were equivalent for external load–SHRZ (large) and SHRZ–sRPE (moderate) across positions, but different for the external load–sRPE correlation (small in backcourt; moderate in frontcourt). Conclusions: In youth basketball, small–large commonalities were found between the training dose (external load) and players’ responses (internal and perceived loads). Practitioners should carefully manage frontcourt players’ training loads because they accumulate greater external and perceived loads than backcourt players do.

Experimental and Numerical Study on Dynamics of Two Footbridges with Different Shapes of Girders

The paper presents the experimental and numerical results of the dynamic system identification and verification of the behavior of two footbridges in Poland. The experimental part of the study involved vibration testing under different scenarios of human-induced load, impulse load, and excitations induced by vibration exciter. Based on the results obtained, the identification of dynamic parameters of the footbridges was performed using the peak-picking method. With the impulse load applied to both structures, determination of their natural vibration frequencies was possible. Then, based on the design drawings, detailed finite element method (FEM) models were developed, and the numerical analyses were carried out. The comparison between experimental and numerical results obtained from the modal analysis showed a good agreement. The results also indicated that both structures under investigation have the first natural bending frequency of the deck in the range of human-induced excitation. Therefore, the risk of excessive structural vibrations caused by pedestrian loading was then analysed for both structures. The vibration comfort criteria for both footbridges were checked according to Sétra guidelines. In the case of the first footbridge, the results showed that the comfort criteria are fulfilled, regardless of the type of load. For the second footbridge, it was emphasized that the structure meets the assumptions of the guidelines for vibration severability in normal use; nevertheless, it is susceptible to excitations induced by synchronized users, even in the case of a small group of pedestrians.

A Novel Method for Diagnosis of Sucker-Rod Pumping Systems Based on the Polished-Rod Load Vibration in Vertical Wells

Summary The pump dynamometer card is a direct reflection of the operating conditions of the downhole pump, which is important for the diagnosis of sucker-rod pumping systems. In this paper, we propose a novel diagnostic method based on the estimation of the parameters from the polished-rod load vibration signal of sucker-rod pumping systems in a vertical well. In this study, we deduce a new analytic solution of the 1D wave equation of the sucker-rod string, which can be used for the predictive and diagnostic analyses. The relationship between the polished-rod load vibration and the pump equivalent impulse load based on the analytic solution is studied, and the diagnostic parameter estimating method is proposed. Therefore, the pump dynamometer card calculated method based on the surface dynamometer card is realized. This study shows that the method is efficient.