The video assistant referee (var) in soccer: where is the biomechanics? / árbitro assistente de vídeo (var) no futebol: onde está a biomecânica?

ABSTRACT The aim of this article is to explore the basic principles of Biomechanics in relation to the objective measurements carried out by the Video Assistant Referee (VAR) operators and systems in soccer. It was presented an overall framework about the determination of kinematical variables, the definition and the sources of error, the understanding of factors contributing to errors in VAR decisions, and prospects for future solutions. To exemplify these concepts, the offside rule was chosen as it offers numerous instances of tools aiding for accurate measurements. Based on consolidated procedures of literature, a discussion about the actual challenges and an suggestions for a fully comprehension and improvement of VAR were provided.

RESUMO O objetivo deste artigo foi explorar os princípios básicos da Biomecânica em relação às medições objetivas realizadas pelos operadores e sistemas do Árbitro Assistente de Vídeo (VAR) no futebol. Foi apresentado uma estrutura geral sobre a determinação das variáveis ​​cinemáticas, a definição e as fontes de erro, a compreensão dos fatores que contribuem para os erros nas decisões do VAR e as perspectivas de soluções futuras. Para exemplificar esses conceitos, a regra do impedimento foi escolhida, pois oferece inúmeras instâncias de ferramentas que requerem medições acuradas. Com base em procedimentos consolidados da literatura, foram apresentadas discussões sobre os atuais desafios e sugestões para compreensão e aprimoramento completos do VAR.

Gender-Related Differences in Reliability of Thorax, Lumbar, and Pelvis Kinematics During Gait in Patients With Non-specific Chronic Low Back Pain

OBJECTIVE: To evaluate test-retest reliability of trunk kinematics relative to the pelvis during gait in two groups (males and females) of patients with non-specific chronic low back pain (NCLBP) using three-dimensional motion capture system. METHODS: A convenience sample of 40 NCLBP participants (20 males and 20 females) was evaluated in two sessions. Participants were asked to walk with self-selected speed and kinematics of thorax and lumbar spine were captured using a 6-infrared-cameras motion-analyzer system. Peak amplitude of displacement and its measurement errors and minimal detectable change (MDC) were then calculated. RESULTS: Intraclass correlation coefficients (ICCs) were relatively constant but small for certain variables (lower lumbar peak flexion in female: inter-session ICC=0.51 and intra-session ICC=0.68; peak extension in male: inter-session ICC=0.67 and intra-session ICC=0.66). The measurement error remained constant and standard error of measurement (SEM) difference was large between males (generally ≤4.8°) and females (generally ≤5.3°). Standard deviation (SD) was higher in females. In most segments, females exhibited higher MDCs except for lower lumbar sagittal movements. CONCLUSION: Although ICCs were sufficiently reliable and constant in both genders during gait, there was difference in SEM due to difference in SD between genders caused by different gait disturbance in chronic low back pain. Due to the increasing tendency of measurement error in other areas of men and women, attention is needed when measuring lumbar motion using the method described in this study.

Quantitative evaluation of the measurement accuracy of 2 three-dimensional facial scanners / 实用口腔医学杂志

Objective:To evaluate the actual measurement accuracy of 2 three-dimensional(3D)facial scanners for real person. Methods:3D digital face models of 1 0 volunteers with normal ficial form were obtained by 3dMD and FaceScan facial scanners respec-tively.The measurement values of 1 0 feature lengths and 5 feature angles were measured on each 3D model by the software respective-ly.The reference values of all characteristics were acquired by line laser scanner (Faro)with high accuracy.Statistical and surveying analysis were taken between the measurement values and reference values.Facial morphology measurement error and actual accuracy of facial scanners were obtained finally.Data were statistically analysed.Results:The length measurement accuracy of 3dMD and FaceS-can was(-0.37 ±0.68)mm and (-0.29 ±0.53)mm(P =0.223),the angle measurement accuracy was (-0.22 ±2.1 4)°and (0.1 2 ±2.69)°(P =0.428),respectively.Conclusion:The 3D data of ficial morphology obtained by the 2 scanners are not signifi-cantly different.

Estudo de calibração do Questionário de Frequência Alimentar para Adolescentes (QFAA) / Calibration study of the Food Frequency Questionnaire for Adolescents (AFFQ)

Para determinar fatores de calibração do Questionário de Frequência Alimentar para Adolescentes (QFAA), participaram do estudo 74 adolescentes de Piracicaba (SP), com idades entre 10 e 14 anos. Dados de consumo alimentar foram levantados por meio de um QFAA e dois recordatórios de 24 horas ajustados pela energia. Foram realizadas análises descritivas, análise de variância com um fator de classificação, coeficientes de correlação de Pearson e regressão linear. A média dos dois recordatórios foi utilizada como referência para calibrar os dados. Os coeficientes de calibração variaram de -0,07 (ferro) a 0,40 (vitamina C), mostrando substancial erro no método de inquérito dietético testado, mas sendo semelhantes aos observados na literatura. Devido ao fato de se apresentarem baixos, indicam a necessidade de reformulação do instrumento para alguns nutrientes, sendo desaconselhada sua aplicação para corrigir informações de ferro e retinol. A metodologia utilizada é capaz de considerar nas análises os erros de mensuração quando suas pressuposições são respeitadas, uma vez que violações desses pressupostos podem levar ao surgimento de outros erros de difícil predição.

In order to establish calibration factors of the Adolescent Food Frequency Questionnaire (AFFQ), 74 boys and girls from Piracicaba (SP, Brazil) with ages ranging from 10 to 14 took part in the study. Dietary intake (assessed by the food frequency questionnaire and 24-hour recall) was assessed and adjusted for energy intake. Descriptive statistics, variance analysis using one classification factor, Pearson's correlation coefficients and linear regression were performed. The average of two 24-hour recalls was used as a reference for calibration of data. Calibration coefficients (λ) ranged from -0.07 (iron) to 0.40 (vitamin C) revealing substantial error in the dietary method tested, albeit similar to those observed in the literature. As these coefficients were low, they indicate the need for reformulating the instrument regarding some nutrients, though application was not considered advisable for correcting information on iron and retinol. The methodology used to calibrate dietary data can consider measurement error in the assessment when its assumptions are respected, since violations of these assumptions may lead to other errors that are difficult to predict.

INFLUENCE OF PERCENT BODY FAT WITH AND WITHOUT WATER IN BIOELECTRICAL IMPEDANCE ANALYSIS / 体力科学

Measuring the bioelectrical impedance (BI) is a simple and non-invasive method for estimating body fat or muscle mass. However, body impedance is affected by variations in the distribution of body fluid without reference to actual body fat or muscle mass. Twenty healthy college students (10 males, 10 females; mean age 21.0±2.3 years) participated in the study. Their mean body mass index was 20.7±2.6 kg/m². Bipolar electrodes were place on all extremities, and InBody 3.0^TM (Biospace Co., Ltd., Seoul, Korea) was used to measure bioelectrical impedance. Each subject remained in a supine position on a comfortable bed between 07:00 and 12:00 except for excretion and measurement of BI. BI was measured hourly using frequencies ranging from 5 to 500 kHz. The subjects refrained from eating, drinking and exercising between 07:00 and 12:00 during the first week of measurements, and drank 6.7 ml/kg of water at 07:00 after the first measurement of BI during a subsequent week of measurements. Bioelectrical impedance was higher in female subjects in all body segments and conditions (<i>p</i><0.01). BI in the right arm was lower than that in the left in all participants (<i>p</i><0.001). The difference between the highest and lowest BI among six measurements was largest in the upper extremities, followed by the lower extremities. Differences in the coefficient of variation CV values of the right arm of both females and males at 50, 250, and 500 kHz during fasting were significantly smaller than after drinking water. Hydration had no effect on the differences in the CV values of the body trunk and lower extremity BI or BI at lower frequencies. BI indicates the possibility of remarkable decrease in variation in the upper extremity BI at higher frequencies by taking 6.7 ml/kg of water at get up and enables minimizing the estimate error of body fat percentage.

Confiabilidade dos dados antropométricos obtidos em crianças atendidas na Rede Básica de Saúde de Alagoas / Reliability of anthropometric data obtained in children seen at the Primary Public Healthcare Service Network in Alagoas, Brazil

Introdução: O monitoramento do crescimento infantil constitui-se em importante ferramenta para a construção de indicadores úteis ao planejamento de políticas e ações de atenção à saúde da criança. Para isso é necessário que os dados antropométricos obtidos apresentem satisfatória confiabilidade. Objetivo: Investigar a confiabilidade dos dados antropométricos produzidos nos Estabelecimentos de Assistência à Saúde (EAS) do SUS em Alagoas. Métodos: Para composição da amostra, sortearam-se 20 dentre os 102 municípios do Estado. Em seguida, dois EAS por município e, nestes, cerca de dez crianças menores de cinco anos. A amostra foi constituída de 40 EAS e 347 crianças. As medidas antropométricas (peso e estatura) foram aferidas (1) na rotina do serviço (S); (2) pelo pesquisador utilizando equipamento padrão (P) e; (3) pesquisador usando equipamentos do serviço (PS). Resultados: A aplicação do teste Kappa indicou concordância "substancial" (K = 0,69) nas classificações de peso-para-idade (PI) entre S e P e "quase perfeita" (K = 0,83) entre PS e P. Quanto à altura-para-idade (AI), a concordância entre S e P foi "discreta" (K = 0,27), passando a "moderada" (K = 0,56) entre PS e P. O Erro Técnico da Medição segundo faixas etárias ( 24 meses) indicou problemas na técnica e nos equipamentos. As medidas de peso corporal obtidas em S foram sistematicamente superestimadas (p < 0,05; teste dos sinais), o que determinou baixa sensibilidade e uma elevada taxa de falsos negativos (38,5 por cento para PI e 57,1 por cento para AI). Conclusão: A baixa confiabilidade observada para a variável altura, desaconselha sua utilização na construção de indicadores de saúde até que os EAS sejam dotados de estadiômetros adequados e pessoal qualificado a utilizá-los. Quanto à variável peso, embora possa ser utilizada, é necessário melhorar sua qualidade por meio da capacitação dos antropometristas e da aquisição e/ou manutenção dos equipamentos.

Introduction: Monitoring child growth is a very important tool not only to build useful indicators for the evaluation and planning of public policies, but also for appropriate care to child health. In order to accomplish that anthropometric data from services need to present satisfactory reliability. Objective: To investigate the reliability of weight and height variables obtained from children at public healthcare services (PHS) of Alagoas. Methods: To build the sample, 20 municipalities were drawn among the 102 of the state. Then, two PHS were drawn per municipality, and in these, about ten children under five years. The final sample consisted of 40 PHS and 347 children. Anthropometric measures (weight and height) were taken (1) during routine service (S); (2) by the researcher using standard equipment (R), and (3) by the researcher using service equipment (RS). Results: The Kappa test indicated a "substantial" level of agreement (K=0.69) in the classifications of weight-for-age (WA) between S and R and "almost perfect" (K = 0.83) in those between RS and R. Regarding height-for-age (HA), the level of agreement between S and R was "fair" (K = 0.27), to "moderate" (K = 0.56) between RS and R. A Technical Measurement Error according to age groups ( 24 months) indicated problems in the technique and equipment. Measurements of body weight obtained in PHS routine were systematically overestimated (p<0.05; sign test), leading to low sensitivity, high specificity and a high rate of false negatives (38.5 percent for WA and 57.1 percent for HA). Conclusion: The low reliability observed for the height variable cautions against its utilization to build health indicators, until the scenario can be improved. The weight variable may be used, but its quality must be improved by training anthropometrists, and through the acquisition and maintenance of equipment.

Test-retest Reliability and Measurement Error in Using A Jamar Dynamometer to Determine Grip Strength for Elderly Men / 中国康复理论与实践

@# ObjectiveTo examine the test-retest reliability and measurement error in using a Jamar dynamometer to determine grip strength for elder men. Methods40 elder men with a mean age of 82 years old volunteered to participate in this study. The grip strength was administered twice using a Jamar dynamometer by specially trained testers; subjects were re-tested at the same time of day a week later by the same testers. ResultsThe infraclass correlation coefficient（ICC） was 0.99. The standard error of measurement (SEM and SEM%) were 1.18～1.69 and 4.11%～6.41%. The smallest real difference (SRD and SRD%) were 3.27～4.68 and 11.39%～17.75%. The Bland-Altman analysis revealed no systematic errors between test and retest. ConclusionThe Jamar dynamometer is reliable and with acceptable measurement errors to determine grip strength for elder men.

Effects of sensor, trials and knee joint variables on electrogoniometric gait recordings / Efeitos das variáveis sensor, coleta e articulação do joelho nos registros eletrogoniométricos da marcha

INTRODUCTION: Different sources of variations, such as electrogoniometer characteristics and procedures, may affect the accuracy and precision of movement measurements during gait. OBJECTIVE: To quantify the variations and compare the effects produced by different sources of variation in electrogoniometric gait recordings: the sensors, procedures (trials) and the knee joint. METHODS: Knee flexion/extension and valgus/varus movements were recorded during gait on the treadmill. The recordings were partitioned into strides and normalized in time using a routine developed in MatLab. Mean curves for the knee during gait were derived from 50 strides, and seven conditions were evaluated: one comparing pairs of sensors; two comparing pairs of different trials (including variations due to sensors); and four comparing the right and left knees (including variations due to sensors and trials). Mean standard deviations of the differences were calculated. To estimate the variations relating to the trial and the knee joint, the compound standard deviations were transformed into variances and split into their components. RESULTS: The variation introduced by pairs of sensors in the same model applied in one trial was smaller than the variation introduced by the same sensor used in two consecutive trials. Furthermore, the variation introduced by the difference between the right and left knees was greater than the variation introduced by the difference between sensors (A and B) and trials (1 and 2). CONCLUSIONS: It is, therefore, preferable to use different sensors in the same data recording (simultaneous) than use the same sensor in two different recordings (consecutive).

INTRODUÇÃO: Diferentes fontes de variação, tais como características do eletrogoniômetro e procedimentos podem afetar a acurácia e precisão das medidas do movimento durante a marcha. OBJETIVO: Quantificar a variação e comparar o efeito das diferentes fontes de variação nos registros eletrogoniométricos da marcha: os sensores, os procedimentos (coletas consecutivas) e a articulação do joelho. MÉTODOS: Movimentos de flexo-extensão e valgo-varo do joelho foram registrados durante a caminhada na esteira. Os registros foram divididos em passadas e normalizados no tempo usando uma rotina desenvolvida em MatLab. As curvas médias do joelho durante a marcha foram derivadas de 50 passadas, e sete condições foram avaliadas: uma para comparar dois sensores; duas para comparar duas diferentes coletas (incluindo a variação do sensor), e quatro para comparar os joelhos direito e esquerdo (incluindo a variação dos sensores e coletas). Os desvios-padrão médios das diferenças foram calculados. Para estimar as variações devido às coletas e à articulação do joelho, os desvios-padrão compostos foram transformados em variâncias e seus componentes isolados. RESULTADOS: A variação introduzida por dois sensores do mesmo modelo aplicados em uma coleta foi menor do que a variação introduzida pelo mesmo sensor usado em duas coletas consecutivas. Ainda, a variação introduzida pela diferença entre os joelhos direito e esquerdo foi maior do que a variação introduzida pela diferença entre os sensores (A e B) e as coletas (1 e 2). CONCLUSÕES: Assim, é preferível usar diferentes sensores na mesma coleta de dados (simultânea) do que usar o mesmo sensor em dois registros diferentes (consecutivos).

Statistical Issues in Genomic Cohort Studies / 예방의학회지

When conducting large-scale cohort studies, numerous statistical issues arise from the range of study design, data collection, data analysis and interpretation. In genomic cohort studies, these statistical problems become more complicated, which need to be carefully dealt with. Rapid technical advances in genomic studies produce enormous amount of data to be analyzed and traditional statistical methods are no longer sufficient to handle these data. In this paper, we reviewed several important statistical issues that occur frequently in large-scale genomic cohort studies, including measurement error and its relevant correction methods, cost-efficient design strategy for main cohort and validation studies, inflated Type I error, gene-gene and gene-environment interaction and time-varying hazard ratios. It is very important to employ appropriate statistical methods in order to make the best use of valuable cohort data and produce valid and reliable study results.

Significance of the Position of the Craniofacial Computed Tomographic Scanning

The computer imaging process is becoming a popular procedure in the research of the craniofacial skeleton. In acquisition of the digital data of computer tomography (CT), the position of the head is likely to vary each time. The difference in head position results in different orientations on actual images, which in turn may result in misinterpretation of the image. The purpose of this study is to point out the importance of position alignment between CT databases before pursuing research by comparing the images of different position alignment To show the significance of the alignment of CT scan, eleven target points were selected from CT scan and the coordinates were obtained from the different position of the aligned CT scan by the nasion, basion, and bilateral external auditory meatus. The target points were divided into three groups-the central points, the lateral points, and the mid points groups, depending on their positional configuration from the mid- sagittal plane. The alignment of CT scan was processed by volume rendering method and the coordinates of target points were taken from the three dimensional images with different position. The aligned CT images rotated by 10 degrees with respect to the X-axis, the (X- and Y-axes), and the (X-, Y-, and Z axes), respectively. Eleven target points were measured from these rotated images one per day, for 10 days, by a plastic surgeon. The mean coordinates from the 10 trials were defined as the gold standard values for the other 10 times measurement. The measurement error(ME) of the central points group was lower than that of the mid points group, and the ME of the mid points group was lower than that of the lateral points group. The ME increased as the distance from the center to target point increased. However the ME of aligned CT images was the lowest of all the rotated cases. For the mean ME of the 11 points, aligned image, the X-axis(X- and Y-axes), and (X-, Y-, and Z-axes) rotation were 0.97, 1.53, 1.62 and 1.77 mm, respectively. Among three rotated cases, ME of the(X-, Y-, and Z-axes) rotation had the highest one. Above results mean that the chance of incorrectly localizing the target points could be significantly reduced if the skull CT images were aligned, in the research of the measurement of craniofacial skeleton from CT scan.

Measurement Errors on Normotensive Subjects in Screening Test / 한국역학회지

BACKGROUND: Blood pressure measurements with a mercury sphygmomanometer serve as the screening test to establish the clinical diagnosis of primary hypertension. But one of the problems of hypertension screening is the variability of blood pressure measurements. METHODS: In order to identify the measurement error of blood pressure through the biennial health screening program of Korea Insurance Medical Corporation, we compared the blood pressure of screening test with true value which defined as the mean of blood pressures taken from the direct contact and twice check-up among normotensive Seoul Cohort participants. RESULTS: Three hundred forty-nine participants had both data of screening measurement and survey of direct contact. The means of difference in systolic and diastolic blood pressure between both data were 8.47 mmHg and 6.54 mmHg, respectively. These results showed statistical significance with paired t-test (p=0.001). CONCLUSION: Our findings indicated that screening measurement of blood pressure had false negative. And if a epidemiologic study about blood pressure used the data of screening test, it should adjust value of systolic and diastolic blood pressure with adding 8 and 7 mmHg, respectively.

A study on the error of tooth size measurements / 대한치과교정학회지

Precise and accurate measuring of tooth size is essential procedure in orthodontic diagnosis. The purpose of this study was to evaluate the reproducibility and accuracy of tooth size measurements with regard to tooth and investigator. Five investigators measured the size of one side of teeth, from central incisor to first molar, on 20 sets of casts that show a moderate degree of crowding. Mesio-distal width was measured with digital vernier calipers in each tooth and this procedure was repeated three times at two weeks interval. To obtain a standard measurement for each tooth, dental casts were cut into individual tooth, and its width was measured with micrometer. The difference between the measurement from dental cast and the standard measurement was defined as the measurement error. Through various statistical analyses, following results were obtained. 1. The reproducibility did not show significant differences with regard to tooth or investigator. 2. The measurement error showed some difference with regard to tooth and investigator. 3. The magnitude of the measurement error showed increasing tendency from anterior to posterior teeth with maximum value in the first molar. 4. While the measurements obtained on study casts generally showed smaller number compared to standard measurements, the direction of the difference showed variability according to tooth or investigator. 5. The measurement errors did not show significant correlations with the degree of crowding. The results of the present study indicate that the possibility of tooth size measurement error should be taken into consideration when diagnosing an orthodontic case.

Factors Affecting Measurement Error of Vertebral Axial Rotation and Reduction of Measurement Error through Training / 대한정형외과학회잡지

PURPOSE: To identify the changes of bony landmarks with rotation and to compare the reliability and accuracy of Perdriolle's method before and after training on the exact bony landmarks. MATERIALS AND METHODS: Simple A-P radiographs were taken with rotation from 5 degree to 50 degree at 5 degree interval using 10 dry human vertebrae (2 sets of T3, T6, T9 8 L3) with no bony abnormality. Axial rotation was measured before and after training on the exact bony landmarks by three observers, twice for each radiographs. Repeated measures of ANOVA were used for inter- 0.05). Incidence of error greater than 5 degree was high at upper thoracic vertebra and 20 degree-40 degree of rotation regardless of training. The effects of training, however, was greatest at T3 and 20 degree-40 degree of rotation. Inter- < intraobserver variance was diminished at T3 and at the rotation between 20 degree-40 degree after training. CONCLUSIONS: We could conclude that training on the exact bony landmarks did not reduce the overall error incidence. Accuracy and reliability, however, was increased at T3 after training and the efficacy of training was more evident in moderate vertebral rotation than in small or large vertebral rotation.

A study on the errors in the cephalometric measurements / 대한치과교정학회지

This study was done to recognize the importance of errors in measurements of cephalometric radiograph and to find the anatomical structures those need special care to select as a reference points through the detection of the systematic errors and estimation of random errors. For this purose, 100 cephalometric radiographs were prepared by usual manner and 61 reference points, and 130 measurement variables were established. Measurement errors were detected and estimated by the comparison of the 25 randomly-selected samples for repeated measurements with the main sample. The following results were obtained: 1. In comparison of the repeated measurements, there were statistical significant differences in 24 variables which were 18.4% of 130 total variables. 2. The frequency of the difference in identification of the reference points between the repeated measurements was very high in the root apex of upper incisor(as), the most posterior wall of maxilla(tu), soft tissue nasion(n'), soft tissue frontal eminence(ft), and adl in airway. 3. After correction of reference points marking until the level of below 59,6 significance, the range of random errors were from 0.67 to 1.71 degree or mm. 4. The variable shown the largest random error was the intenncisal angle(ILs-lLi). 5. Measurement errors were mainly caused by the lack of precision in anatomic definitions and obscure radiographic image. From the above results, the author could find the high possibility of errors in cephalometric measurements and from this point, we should include error analysis in all the studies concerning measurments. In is essential to have a concept of error analysis not only for the investigator but also for a reader of other articles.