Análisis del golpeo de balón y su relación con el salto vertical en futbolistas juveniles de alto nivel

El rendimiento en acciones explosivas como el golpeo de balón y el salto vertical es de gran relevancia en el fútbol. Los objetivos del presente estudio fueron: 1) Estudiar la secuencia del golpeo en futbolistas jóvenes de alto nivel, y, 2) analizar las posibles relaciones existentes entre el golpeo de balón y el salto vertical. 21 jugadores de alto nivel (16,1 ± 0,2 años) llevaron a cabo un test de salto vertical con contramovimiento (CMJ) y un test de golpeo de balón con la máxima potencia. Los datos fueron registrados mediante una plataforma de fuerzas (Dinascan IBV) y un sistema de captura automática del movimiento (Vicon). Con este estudio, se aporta información sobre la cinemática del golpeo en futbolistas juveniles de alto nivel. En función de los resultados obtenidos, se puede afirmar que la secuencia temporal de máximos de velocidad sucede desde el extremo más proximal al más distal, incrementándose la velocidad. La ausencia de relación entre el golpeo y el salto sugiere el trabajo de fuerza explosiva específico para la mejora de cada una de ellas

The application of biomechanics to penalty corner drag-flick training: a case of Study

The penalty corner is one of the most important game situations in field hockey with one third of all goals resulting from this tactical situation. The aim of this study was to develop and apply a training method, based on previous studies, to improve the drag- flick skill on a young top-class field hockey player. A young top-class player exercised three times per week using specific drills over a four week period. A VICON optoelectronic system (Oxford Metrics, Oxford, UK) was employed to capture twenty drag-flicks, with six cameras sampling at 250 Hz, prior and after the training period. In order to analyze pre- and post-test differences a dependent t-test was carried out. Angular velocities and the kinematic sequence were similar to previous studies. The player improved (albeit not significantly) the angular velocity of the stick. The player increased front foot to the ball at T1 (p < 0.01) and the drag-flick distances. The range of motion from the front leg decreased from T1 to T6 after the training period (p < 0.01). The specific training sessions conducted with the player improved some features of this particular skill. This article shows how technical knowledge can help with the design of training programs and whether some drills are more effective than others

Effect of positioning on the accuracy of decision making of association football top-class referees and assistant referees during competitive matches

The aim of this study was to examine the effect of positioning on the correctness of decision making of top-class referees and assistant referees during international games. Match analyses were carried out during the Fe´de´ration Internationale de Football Association (FIFA) Confederations Cup 2009 and 380 foul play incidents and 165 offside situations were examined. The error percentage for the referees when indicating the incidents averaged 14%. The lowest error percentage occurred in the central area of the field, where the collaboration of the assistant referee is limited, and was achieved when indicating the incidents from a distance of 11–15 m, whereas this percentage peaked (23%) in the last 15-min match period. The error rate for the assistant referees was 13%. Distance of the assistant referee to the offside line did not have an impact on the quality of the offside decision. The risk of making incorrect decisions was reduced when the assistant referees viewed the offside situations from an angle between 46 and 608. Incorrect offside decisions occurred twice as often in the second as in the first half of the games. Perceptual-cognitive training sessions specific to the requirements of the game should be implemented in the weekly schedule of football officials to reduce the overall error rate

La Eficacia del Efecto Látigo en el Dragflick en Hockey Hierba

El penalty córner es una de las jugadas más importantes en el hockey hierba. El drag-flick es la técnica de golpeo más eficaz en las jugadas de penalty córner (McLaughin, 1997). Los objetivos del presente estudio fueron el describir los parámetros cinemáticos del drag-flick en jugadores de nivel internacional y analizar las diferencias intergénero. La muestra fueron trece sujetos, un modelo, seis hombres y seis mujeres. El sistema de captura automático VICON registró 20 lanzamientos de cada jugador con una frecuencia de muestreo de 250 Hz. Las velocidades máximas angulares de las caderas, hombros y stick fueron superiores (p<0.01) en el modelo que en ambos grupos de género. Mediante la comparación estadística del modelo con ambos grupos de género se han podido determinar las claves de este gesto técnico, siendo necesario un movimiento hacia atrás del stick (efecto látigo) antes de la aceleración de caderas y hombros, para terminar el gesto con la máxima aceleración del stick

Valoración de la Fuerza Explosiva General y Específica en Futbolistas Juveniles de Alto Nivel.

La fuerza explosiva es una capacidad física fundamental en el fútbol, por lo que su valoración resulta importante para el control y planificación del entrenamiento. El objetivo de este estudio fue valorar la Fuerza explosiva general y específica en futbolistas juveniles de alto nivel. 21 jugadores pertenecientes a un club de alto nivel (16,1 ± 0,2 años; 1,77 ± 0,06 m; 67,7 ± 6,3 kg) llevaron a cabo un test general de fuerza explosiva (salto vertical con contra movimiento -CMJ) y un test específico (golpeo de balón con la máxima potencia), obteniéndose, a través de una plataforma de fuerzas Dinascan IBV y de un sistema de captura automática del movimiento en 3D Vicon, datos de diversas variables relacionadas con la fuerza explosiva, siendo posteriormente registrados en una hoja de cálculo Excel diseñada al efecto. Se observa que los tests llevados a cabo proporcionan, en un corto periodo de tiempo, una información de gran relevancia para el control y la planificación del entrenamiento con el objetivo de intentar optimizar el rendimiento de los futbolistas

El patrón de movimiento en el swing de golf en jóvenes promesas

Introducción: El swing de golf es una destreza que podríamos catalogar de golpeo de velocidad donde el objetivo es que la cara del palo alcance la máxima velocidad en el momento del impacto. Objetivos: Analizar la secuencia temporal del swing de golf y determinar su patrón de movimiento. Métodos: Se han analizado biomecánicamente 10 golpeos de 4 jugadores promesas, mediante el sistema de fotogrametría 3D Vicon Oxford Metrics® de captura automática. Resultados: En primer lugar se ha podido comprobar que los valores absolutos de velocidades lineales eran mayores en los chicos que en las chicas. El análisis de las 2 fases del swing indica que la fase de aceleración downswing presenta una variabilidad menor que el backswing. El análisis de la secuencia temporal de máximos alcanzados en las velocidades lineales de los segmentos muestra que sus acciones siguen un orden diferente en función del sexo. La secuencia en los chicos empieza por el movimiento de caderas y sigue con el codo izquierdo, el hombro izquierdo y el palo; en las chicas, las caderas y el codo izquierdo actúan simultáneamente seguidos del hombro izquierdo y del palo. En cambio, las secuencias de velocidades angulares encontradas seguían en ambos sexos el mismo orden: primero el giro de caderas, luego el giro de hombros y por último la aceleración del palo. Esta secuencia de acciones se encontraba más separada en el tiempo en los hombres que en las mujeres. Conclusiones: Se hallaron los patrones del movimiento mediante fórmulas discriminantes en ambos sexos, capaces de predecir si el golpeo sería “bueno” o “malo” siguiendo el criterio de rendimiento marcado en la velocidad de la cabeza del palo. Introduction: The golf swing is a skill that could be classified as high velocity hitting in which the main goal is that the head of the golf club reaches its maximum velocity at the moment of impact. Aims: To analyze the timing sequence of the golf swing and to identify the movement pattern of this skill. Methods: Ten golf swings executed by four young players were biomechanically analyzed. Automatic capture with Vicon Oxford Metrics® was used. Results: The absolute values of the linear velocities were higher in men than in women. In the interval analysis, the downswing showed less variation than the backswing. Analysis of the maximum speed timing sequence revealed a different order depending on gender. In men, the sequence started with the hip movement, followed by the left elbow, left shoulder and the club head. In women, the hips and left elbow moved simultaneously, followed by the left shoulder and the club head. In contrast, the angular velocity sequences followed the same order in both genders: first the hip turn, then the shoulder turn, and finally the golf club head acceleration. These key events were more separated in the time line in men than in women. Conclusions: Movement patterns were found through discriminatory formulae in both genders, which were able to predict whether the golf swing was “good” or “bad”, taking the club head speed as the performance criterion

Familial hypercholesterolaemia in children and adolescents from 48 countries: a cross-sectional study

Background: Approximately 450 000 children are born with familial hypercholesterolaemia worldwide every year, yet only 2·1% of adults with familial hypercholesterolaemia were diagnosed before age 18 years via current diagnostic approaches, which are derived from observations in adults. We aimed to characterise children and adolescents with heterozygous familial hypercholesterolaemia (HeFH) and understand current approaches to the identification and management of familial hypercholesterolaemia to inform future public health strategies. Methods: For this cross-sectional study, we assessed children and adolescents younger than 18 years with a clinical or genetic diagnosis of HeFH at the time of entry into the Familial Hypercholesterolaemia Studies Collaboration (FHSC) registry between Oct 1, 2015, and Jan 31, 2021. Data in the registry were collected from 55 regional or national registries in 48 countries. Diagnoses relying on self-reported history of familial hypercholesterolaemia and suspected secondary hypercholesterolaemia were excluded from the registry; people with untreated LDL cholesterol (LDL-C) of at least 13·0 mmol/L were excluded from this study. Data were assessed overall and by WHO region, World Bank country income status, age, diagnostic criteria, and index-case status. The main outcome of this study was to assess current identification and management of children and adolescents with familial hypercholesterolaemia. Findings: Of 63 093 individuals in the FHSC registry, 11 848 (18·8%) were children or adolescents younger than 18 years with HeFH and were included in this study; 5756 (50·2%) of 11 476 included individuals were female and 5720 (49·8%) were male. Sex data were missing for 372 (3·1%) of 11 848 individuals. Median age at registry entry was 9·6 years (IQR 5·8-13·2). 10 099 (89·9%) of 11 235 included individuals had a final genetically confirmed diagnosis of familial hypercholesterolaemia and 1136 (10·1%) had a clinical diagnosis. Genetically confirmed diagnosis data or clinical diagnosis data were missing for 613 (5·2%) of 11 848 individuals. Genetic diagnosis was more common in children and adolescents from high-income countries (9427 [92·4%] of 10 202) than in children and adolescents from non-high-income countries (199 [48·0%] of 415). 3414 (31·6%) of 10 804 children or adolescents were index cases. Familial-hypercholesterolaemia-related physical signs, cardiovascular risk factors, and cardiovascular disease were uncommon, but were more common in non-high-income countries. 7557 (72·4%) of 10 428 included children or adolescents were not taking lipid-lowering medication (LLM) and had a median LDL-C of 5·00 mmol/L (IQR 4·05-6·08). Compared with genetic diagnosis, the use of unadapted clinical criteria intended for use in adults and reliant on more extreme phenotypes could result in 50-75% of children and adolescents with familial hypercholesterolaemia not being identified. Interpretation: Clinical characteristics observed in adults with familial hypercholesterolaemia are uncommon in children and adolescents with familial hypercholesterolaemia, hence detection in this age group relies on measurement of LDL-C and genetic confirmation. Where genetic testing is unavailable, increased availability and use of LDL-C measurements in the first few years of life could help reduce the current gap between prevalence and detection, enabling increased use of combination LLM to reach recommended LDL-C targets early in life

Canagliflozin and renal outcomes in type 2 diabetes and nephropathy

BACKGROUND Type 2 diabetes mellitus is the leading cause of kidney failure worldwide, but few effective long-term treatments are available. In cardiovascular trials of inhibitors of sodium–glucose cotransporter 2 (SGLT2), exploratory results have suggested that such drugs may improve renal outcomes in patients with type 2 diabetes. METHODS In this double-blind, randomized trial, we assigned patients with type 2 diabetes and albuminuric chronic kidney disease to receive canagliflozin, an oral SGLT2 inhibitor, at a dose of 100 mg daily or placebo. All the patients had an estimated glomerular filtration rate (GFR) of 30 to &lt;90 ml per minute per 1.73 m2 of body-surface area and albuminuria (ratio of albumin [mg] to creatinine [g], &gt;300 to 5000) and were treated with renin–angiotensin system blockade. The primary outcome was a composite of end-stage kidney disease (dialysis, transplantation, or a sustained estimated GFR of &lt;15 ml per minute per 1.73 m2), a doubling of the serum creatinine level, or death from renal or cardiovascular causes. Prespecified secondary outcomes were tested hierarchically. RESULTS The trial was stopped early after a planned interim analysis on the recommendation of the data and safety monitoring committee. At that time, 4401 patients had undergone randomization, with a median follow-up of 2.62 years. The relative risk of the primary outcome was 30% lower in the canagliflozin group than in the placebo group, with event rates of 43.2 and 61.2 per 1000 patient-years, respectively (hazard ratio, 0.70; 95% confidence interval [CI], 0.59 to 0.82; P=0.00001). The relative risk of the renal-specific composite of end-stage kidney disease, a doubling of the creatinine level, or death from renal causes was lower by 34% (hazard ratio, 0.66; 95% CI, 0.53 to 0.81; P&lt;0.001), and the relative risk of end-stage kidney disease was lower by 32% (hazard ratio, 0.68; 95% CI, 0.54 to 0.86; P=0.002). The canagliflozin group also had a lower risk of cardiovascular death, myocardial infarction, or stroke (hazard ratio, 0.80; 95% CI, 0.67 to 0.95; P=0.01) and hospitalization for heart failure (hazard ratio, 0.61; 95% CI, 0.47 to 0.80; P&lt;0.001). There were no significant differences in rates of amputation or fracture. CONCLUSIONS In patients with type 2 diabetes and kidney disease, the risk of kidney failure and cardiovascular events was lower in the canagliflozin group than in the placebo group at a median follow-up of 2.62 years

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals &lt;1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Reliability of the Brzycki Formula to Estimate 1RM Bench Press and Half-Squat Between Collegiate Men and Women

BACKGROUND: The determination of the 1-repetition maximum (1RM) is one of the most frequently performed evaluations to assess maximal dynamic strength in athletes. Several formulas have been proposed to estimate the 1RM. The objective of this study was to compare 1RM measurement with a 1RM estimate obtained from the Brzycki formula to estimate 1RM bench press and half-squat between young men and women. METHODS: Forty-six male and 15 female sport sciences undergraduates performed 3RM in bench press and 3RM in half-squat. in two sessions. In different days, participants performed the 1RM test of each exercise. A two-way (gender x exercise) ANOVA was applied to analyze the difference between the estimate and the actual 1RM. The level of significance set for the study was P\u3c0.05. RESULTS: Differences (P\u3c0.001) between the estimate and the 1RM was found both in half-squat (9.3±11.1 kg) and bench press (4.6±6.2 kg) for both the whole group. No significant differences were found in the interaction gender x exercise, not in absolute terms (P=0.23; partial η2=0.01) or in percentage (P=0.34; partial η2=0.007). CONCLUSIONS: Estimating 1RM by Brzycki formula according to how it has been conducted in this study is not different in young men and women in relation to the exercise performed: half-squat and bench press. However, the estimate was different from the actual 1RM for both exercises