RESUMO
Palucci Vieira, LH, Aquino, R, Moura, FA, Barros, RMLd, Arpini, VM, Oliveira, LdP, Bedo, BLdS, and Pereira Santiago, PR. Team dynamics, running, and skill-related performances of Brazilian U11 to professional soccer players during official matches. J Strength Cond Res 33(8): 2202-2216, 2019-Analyses of movements during soccer competition have been used previously to help develop conditioning programs. However, this has not been extensively studied in youth populations. Therefore, the purposes of this study were to examine (1) dynamics of collective tactical movements, (2) running, and (3) skill-related performances during soccer matches disputed by children to senior players. A total of 120 Brazilian players in the age groups U11, U13, U15, U17, U20, and professional (PRO) were monitored during official competition matches (N = 12). Using semiautomatic video-based tracking (30 Hz), match running variables including total distance traveled, average speed, maximum sprint speed, and high-intensity activities were evaluated. Tactical metrics were computed as team surface area, spread, and median frequency. Through notational analysis, technical skills such as involvements with the ball, passes, ball touches, duels, and goal attempts were also recorded. One-way analysis of variance and magnitude-based inferences were used to detect differences between ages. Although the average speed, team surface area, and spread tended to present stabilized increases from the U15 (e.g., U15 > U13 > U11), maximal sprinting speed (PRO > U17 > U15, U13, U11) and percentage at very high-intensity activities (U20 > PRO, U17 > U15 > U13 > U11) demonstrated continuous gains. Median frequencies were higher in the younger groups (U13, U15, U17 > U20, PRO), although the percentage of successful passes was higher in the older groups (PRO > U17, U15 > U13, U11). We concluded that Brazilian U11 to PRO players present different performance profiles for running, collective movement dynamics, and technical skills, and that the rate of development regarding these components varies. Coaches should be aware of these differences to select and adapt training content for each age group.
Assuntos
Desempenho Atlético/fisiologia , Movimento/fisiologia , Corrida/fisiologia , Futebol/fisiologia , Adolescente , Adulto , Fatores Etários , Brasil , Criança , Humanos , Masculino , Gravação de Videoteipe , Adulto JovemRESUMO
Action sport cameras (ASC) have achieved a large consensus for recreational purposes due to ongoing cost decrease, image resolution and frame rate increase, along with plug-and-play usability. Consequently, they have been recently considered for sport gesture studies and quantitative athletic performance evaluation. In this paper, we evaluated the potential of two ASCs (GoPro Hero3+) for in-air (laboratory) and underwater (swimming pool) three-dimensional (3D) motion analysis as a function of different camera setups involving the acquisition frequency, image resolution and field of view. This is motivated by the fact that in swimming, movement cycles are characterized by underwater and in-air phases what imposes the technical challenge of having a split volume configuration: an underwater measurement volume observed by underwater cameras and an in-air measurement volume observed by in-air cameras. The reconstruction of whole swimming cycles requires thus merging of simultaneous measurements acquired in both volumes. Characterizing and optimizing the instrumental errors of such a configuration makes mandatory the assessment of the instrumental errors of both volumes. In order to calibrate the camera stereo pair, black spherical markers placed on two calibration tools, used both in-air and underwater, and a two-step nonlinear optimization were exploited. The 3D reconstruction accuracy of testing markers and the repeatability of the estimated camera parameters accounted for system performance. For both environments, statistical tests were focused on the comparison of the different camera configurations. Then, each camera configuration was compared across the two environments. In all assessed resolutions, and in both environments, the reconstruction error (true distance between the two testing markers) was less than 3mm and the error related to the working volume diagonal was in the range of 1:2000 (3×1.3×1.5m3) to 1:7000 (4.5×2.2×1.5m3) in agreement with the literature. Statistically, the 3D accuracy obtained in the in-air environment was poorer (p<10-5) than the one in the underwater environment, across all the tested camera configurations. Related to the repeatability of the camera parameters, we found a very low variability in both environments (1.7% and 2.9%, in-air and underwater). This result encourage the use of ASC technology to perform quantitative reconstruction both in-air and underwater environments.
Assuntos
Processamento de Imagem Assistida por Computador , Movimento/fisiologia , Gravação em Vídeo/instrumentação , Calibragem , Piscinas , ÁguaRESUMO
Action sport cameras (ASC) are currently adopted mainly for entertainment purposes but their uninterrupted technical improvements, in correspondence of cost decreases, are going to disclose them for three-dimensional (3D) motion analysis in sport gesture study and athletic performance evaluation quantitatively. Extending this technology to sport analysis however still requires a methodologic step-forward to making ASC a metric system, encompassing ad-hoc camera setup, image processing, feature tracking, calibration and 3D reconstruction. Despite traditional laboratory analysis, such requirements become an issue when coping with both indoor and outdoor motion acquisitions of athletes. In swimming analysis for example, the camera setup and the calibration protocol are particularly demanding since land and underwater cameras are mandatory. In particular, the underwater camera calibration can be an issue affecting the reconstruction accuracy. In this paper, the aim is to evaluate the feasibility of ASC for 3D underwater analysis by focusing on camera setup and data acquisition protocols. Two GoPro Hero3+ Black (frequency: 60Hz; image resolutions: 1280×720/1920×1080 pixels) were located underwater into a swimming pool, surveying a working volume of about 6m3. A two-step custom calibration procedure, consisting in the acquisition of one static triad and one moving wand, carrying nine and one spherical passive markers, respectively, was implemented. After assessing camera parameters, a rigid bar, carrying two markers at known distance, was acquired in several positions within the working volume. The average error upon the reconstructed inter-marker distances was less than 2.5mm (1280×720) and 1.5mm (1920×1080). The results of this study demonstrate that the calibration of underwater ASC is feasible enabling quantitative kinematic measurements with accuracy comparable to traditional motion capture systems.
Assuntos
Processamento de Imagem Assistida por Computador/instrumentação , Movimento , Esportes , Natação/fisiologia , Gravação em Vídeo/instrumentação , Fenômenos Biomecânicos , Calibragem/normas , Humanos , Processamento de Imagem Assistida por Computador/métodos , Gravação em Vídeo/métodos , Água , Fluxo de TrabalhoRESUMO
The purposes of this study were to characterise the total space covered and the distances between players within teams over ten Brazilian First Division Championship matches. Filmed recordings, combined with a tracking system, were used to obtain the trajectories of the players (n = 277), before and after half-time. The team surface area (the area of the convex hull formed by the positions of the players) and spread (the Frobenius norm of the distance-between-player matrix) were calculated as functions of time. A Fast Fourier Transform (FFT) was applied to each time series. The median frequency was then calculated. The results of the surface area time series median frequencies for the first half (0.63 ± 0.10 cycles · min⻹) were significantly greater (P < 0.01) than the second-half values (0.47 ± 0.14 cycles · min⻹). Similarly, the spread variable median frequencies for the first half (0.60 ± 0.14 cycles · min⻹) were significantly greater (P < 0.01) than the second-half values (0.46 ± 0.16 cycles · min⻹). The median frequencies allowed the characterisation of the time series oscillations that represent the speed at which players distribute and then compact their team formation during a match. This analysis can provide insights that allow coaches to better control the team organisation on the pitch.
Assuntos
Desempenho Atlético , Corrida , Futebol , Análise e Desempenho de Tarefas , Brasil , Comportamento Competitivo , HumanosRESUMO
In this study we aim at investigating the applicability of underwater 3D motion capture based on submerged video cameras in terms of 3D accuracy analysis and trajectory reconstruction. Static points with classical direct linear transform (DLT) solution, a moving wand with bundle adjustment and a moving 2D plate with Zhang's method were considered for camera calibration. As an example of the final application, we reconstructed the hand motion trajectories in different swimming styles and qualitatively compared this with Maglischo's model. Four highly trained male swimmers performed butterfly, breaststroke and freestyle tasks. The middle fingertip trajectories of both hands in the underwater phase were considered. The accuracy (mean absolute error) of the two calibration approaches (wand: 0.96 mm - 2D plate: 0.73 mm) was comparable to out of water results and highly superior to the classical DLT results (9.74 mm). Among all the swimmers, the hands' trajectories of the expert swimmer in the style were almost symmetric and in good agreement with Maglischo's model. The kinematic results highlight symmetry or asymmetry between the two hand sides, intra- and inter-subject variability in terms of the motion patterns and agreement or disagreement with the model. The two outcomes, calibration results and trajectory reconstruction, both move towards the quantitative 3D underwater motion analysis.
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Mãos/fisiologia , Processamento de Imagem Assistida por Computador , Modelos Teóricos , Movimento/fisiologia , Natação/fisiologia , Gravação em Vídeo/métodos , Fenômenos Biomecânicos , Calibragem , Gráficos por Computador , Apresentação de Dados , Voluntários Saudáveis , Humanos , Masculino , Movimento (Física) , Postura/fisiologia , Natação/educaçãoRESUMO
This study investigated the effects of 1 year of regular wheelchair rugby training on the pulmonary function of subjects with tetraplegia. A total of 15 male subjects with tetraplegia participated in this study and were divided into an experimental group of rugby players (n = 8) and a control group (n = 7) of sedentary tetraplegic subjects. Both groups underwent spirometry, and the experimental group was tested before and after participating of a regular 1-year program of wheelchair rugby training. At the beginning of the training program, all the subjects presented reduced pulmonary function compared with predicted values (p < 0.05) for healthy subjects. There were a significant increase in forced vital capacity (FVC), forced expired volume after 1 second (FEV1), and maximal voluntary ventilation (MVV, p < 0.05) values after 1 year of regular wheelchair rugby training. The regression analysis between total training time and spirometric variables FVC (r = 0.97, p < 0.0001) and MVV (r = 0.58, p = 0.02) revealed that the players with longer training time had higher pulmonary function values. This study showed that regular wheelchair rugby training can improve the pulmonary function of subjects with spinal cord injuries.
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Futebol Americano/fisiologia , Pulmão/fisiopatologia , Educação Física e Treinamento , Quadriplegia/fisiopatologia , Traumatismos da Medula Espinal/fisiopatologia , Cadeiras de Rodas , Adulto , Estudos de Casos e Controles , Humanos , Masculino , Análise de Regressão , Testes de Função Respiratória , Estatísticas não Paramétricas , Resultado do TratamentoRESUMO
The purpose of this paper was to understand which differences long-term swimming training can cause on trunk mechanics during breathing and how these differences are related to the years of swimming training. The variations and coordination among trunk compartments were considered as target movement patterns. Video-based plethysmography was utilised for data acquisition and pre-processing. A group of swimmers, who followed a long-term intensive swimming training previously to this study, was compared with a non-swimmer control group. The participants of both groups performed quiet breathing and vital capacity tests. From the compartmental volumes associated with each breathing curves, the relative amplitude and cross-correlation among these volumetric time-varying signals were calculated, in order to analyse the relative partial volume variation and the coordination among trunk compartments involved in respiration. The results of a Mixed-ANOVA test (P ≤ 0.05) revealed higher coefficient of variation (P < 0.001) and correlations among trunk compartments in the swimmers group when vital capacity was performed. Significant linear regression was found between the years of swim training and the coefficients of variation and correlation. The results suggest that after long periods of intensive swim training, athletes might develop specific breathing patterns featuring higher volume variations in the abdominal region and more coordination among compartments involved in forced respiratory tasks such as vital capacity.
Assuntos
Pulmão/fisiologia , Educação Física e Treinamento , Respiração , Natação/fisiologia , Capacidade Vital , Adolescente , Adulto , Análise de Variância , Fenômenos Biomecânicos , Humanos , Modelos Lineares , Masculino , Movimento , Pletismografia , Tronco , Adulto JovemRESUMO
OBJECTIVE: The aim of this study was to evaluate the effects of wheelchair sports on respiratory muscle strength and the thoracic mobility of individuals with spinal cord injury. DESIGN: Thirty male subjects with chronic spinal cord injury (American Spinal Injury Association Impairment Scale grade A) took part in the study and were divided into four groups: sedentary subjects with quadriplegia (S-QUAD, n = 7), wheelchair rugby athletes with quadriplegia (A-QUAD, n = 8), sedentary subjects with paraplegia (S-PARA, n = 6), and wheelchair basketball athletes with paraplegia (A-PARA, n = 9). The main outcome measures were maximal inspiratory and expiratory pressure and the respiratory coefficients at the axillary and xiphoid levels. RESULTS: A-QUAD group presented values significantly higher for all respiratory variables studied compared with the S-QUAD group. No significant differences in any of the respiratory variables were observed between S-PARA and A-PARA groups. There was a negative correlation between spinal cord injury level and respiratory variables for the S-QUAD and S-PARA groups. There were positive correlations in the A-QUAD group between time of training and maximal inspiratory pressure (adjusted R = 0.84; P = 0.001) and respiratory coefficients at the axillary level (adjusted R = 0.80; P = 0.002). CONCLUSIONS: Physical training seems to have a positive influence on respiratory muscle strength and thoracic mobility, especially in subjects with quadriplegia.
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Desempenho Atlético , Força Muscular/fisiologia , Músculos Respiratórios/fisiologia , Traumatismos da Medula Espinal/reabilitação , Esportes/fisiologia , Cadeiras de Rodas/estatística & dados numéricos , Adulto , Basquetebol/fisiologia , Brasil , Estudos de Coortes , Futebol Americano/fisiologia , Humanos , Masculino , Paraplegia/diagnóstico , Paraplegia/reabilitação , Resistência Física/fisiologia , Testes de Função Respiratória , Mecânica Respiratória , Traumatismos da Medula Espinal/diagnóstico , Adulto JovemRESUMO
The purpose of this study was to compare three camera calibration approaches applied to underwater applications: (1) static control points with nonlinear DLT; (2) moving wand with nonlinear camera model and bundle adjustment; (3) moving plate with nonlinear camera model. The DVideo kinematic analysis system was used for underwater data acquisition. The system consisted of two gen-locked Basler cameras working at 100 Hz, with wide angle lenses that were enclosed in housings. The accuracy of the methods was compared in a dynamic rigid bar test (acquisition volume-4.5×1×1.5 m(3)). The mean absolute errors were 6.19 mm for the nonlinear DLT, 1.16 mm for the wand calibration, 1.20 mm for the 2D plate calibration using 8 control points and 0.73 mm for the 2D plane calibration using 16 control points. The results of the wand and 2D plate camera calibration methods were less associated to the rigid body position in the working volume and provided better accuracy than the nonlinear DLT. Wand and 2D plate camera calibration methods presented similar and highly accurate results, being alternatives for underwater 3D motion analysis.
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Discos Compactos/normas , Natação , Adulto , Calibragem , HumanosRESUMO
The aim of the present paper is to propose and evaluate an automatically trained cascaded boosting detector algorithm based on morphological segmentation for tracking handball players. The proposed method was able to detect correctly 84% of players when applied to the second period of that same game used for training and 74% when applied to a different game. Furthermore, the analysis of the automatic training using boosting detector revealed general results such as the training time initially increased with the number of figures used, but as more figures were added, the training time decreased. Automatic morphological segmentation has shown to be a fast and efficient method for selecting image regions for the boosting detector and allowed an improvement in the automatic tracking of handball players.