The effects of playing two consecutive matches in the shoulder rotational profiles of elite youth badminton players.

OBJECTIVE: The aim of the present study was to analyse the effects of playing two badminton matches on the same day on the shoulder profile (i.e., range of motion (ROM) and strength) of young badminton players. DESIGN: Cross-sectional study. SETTING: Indoor sports facility. PARTICIPANTS: Thirty-one elite junior badminton players (age 16.6 ±â€¯1.0 years, body mass 63.9 ±â€¯6.1 kg, height 174.8 ±â€¯6.1 cm), including 19 boys and 12 girls. MAIN OUTCOME MEASURES: Shoulder passive internal rotation (IR) and external rotation (ER) ROM as well as shoulder IR/ER maximal isometric strength were measured before and after a competition including two competitive matches. RESULTS: Significant decreases (p < 0.05) were found in the shoulder ROM (i.e., dominant and non-dominant ER ROMs as well as in the dominant and non-dominant total arc of motion [TAM]) in boys, while in girls, significant increases (p < 0.05) were found in the non-dominant ER absolute strength, with significant decreases were found in the non-dominant ER ROM and the non-dominant TAM. CONCLUSION: Playing two badminton matches on the same day led to gender-specific changes on the shoulder profile (i.e., ROM and strength) of young elite badminton players, with more impact on the shoulder profile of boys compared to girls.

Diferencias en el comportamiento visual y motor de tenistas en laboratorio y en pista de tenis / Visual and motor behavior of tennis players in laboratory versus on tennis-court

El estudio compara el comportamiento visual y motor de 40 tenistas noveles en laboratorio (2D) y en pista de tenis (3D) cuando visualizan una secuencia de passing-shots ejecutada por un oponente experto desde el fondo de la pista. Los tenistas deben responder rápida y precisamente mediante un armado de volea de derecha o de revés según la dirección del golpeo. Para el registro del comportamiento visual, se utiliza el sistema tecnológico ASL SE 5000, mientras que para el comportamiento motor, se adapta un sistema tecnológico para el entrenamiento de las habilidades motoras abiertas. Las variables dependientes son: el tiempo de fijación visual en cada localización corporal o espacial; el tiempo de reacción y de movimiento, tiempo de respuesta (o suma de las dos variables anteriores), y eficacia de la respuesta. Los resultados evidencian que la muestra de tenistas noveles se fija más en la zona central del cuerpo del oponente (tronco, cadera) y son más rápidos en 2D. En cambio, en 3D se fijan más en la zona superior del oponente (cabeza, hombros). Por lo tanto, los tenistas desarrollan un comportamiento visual y motor diferenciado según perciban el movimiento del oponente de forma videoproyectada o en pista de tenis. Se recomienda diseñar tareas representativas en laboratorio que ofrezcan a los deportistas procesos de percepción y de acción similares a situaciones reales de competición.

This study addresses the visual and motor behavior, and success rate, of 40 novice tennis players in a laboratory setting and an on-court situation when viewing a passing-shots rally performed by an expert tennis player located at the back line of the court. The tennis players had to move fast and quickly through forehand or backhand volleys. Visual search strategies were recorded with an ASL SE5000 eye tracking system, and a computerized system was used to analyze the time parameters of the motor response. The dependent variables are the time of visual fixation on the corporal or spatial locations, reaction and movement times, response time (or the sum of the two variables), and success rate of the responses. The results show that the sample of novice players were faster in 2D and fixed more time on the central area of the opponent body (e.g., trunk, hip). Thus, novice players fixed more on the upper body of the opponent (e.g., head, shoulders) in 3D. Therefore, tennis players develop a differentiated visual and motor behavior according to the way they perceive the opponent's movement, whether in a video projection or on the tennis court. It is recommended to carry out representative tasks in the laboratory to provide perceptive and motor processes similar to real situations.

Visual availability, balance performance and movement complexity in dancers.

Research regarding the complex fluctuations of postural sway in an upright standing posture has yielded controversial results about the relationship between complexity and the capacity of the system to generate adaptive responses. The aim of this study is to compare the performance and complexity of two groups with different levels of expertise in postural control during a balance task. We examined the balance ability and time varying (dynamic) characteristics in a group of 18 contemporary dancers and 30 non-dancers in different visual conditions. The task involved maintaining balance for 30s on a stability platform with opened or closed eyes. The results showed that dancers exhibited greater balance ability only in open eyes task than non-dancers. We also observed a lower performance in both groups during the test with closed eyes, but only dancers reduced their complexity in closed eyes task. The main conclusion is that the greater postural control exhibited by dancers depends on the availability of visual information.

Effect of increasing difficulty in standing balance tasks with visual feedback on postural sway and EMG: complexity and performance.

Studies about the relationship between complexity and performance in upright standing balance have yielded mixed results and interpretations. The aim of the present study was to assess how the increasing difficulty in standing balance task affects performance and the complexity of postural sway and neuromuscular activation. Thirty-two young healthy participants were asked to stand still on a stability platform with visual feedback in three levels of difficulty. EMG signals from gastrocnemius medialis, tibialis anterior, rectus femoris and biceps femoris were measured with surface electromyography. As task difficulty increased, the amplitude of postural sway also increased. In the antero-posterior axis, Fuzzy Entropy (complexity) of postural sway decreased from the stable condition to the medium instability condition, and increased again at the highest instability condition. Fuzzy Entropy in the medio-lateral axis was higher in the stable condition; however, no differences were observed between the two instability conditions. Lower values of Fuzzy Entropy in postural sway during stable condition correlated with greater percent increases in postural sway in medio-lateral and antero-posterior axis from the standing still condition to the highest instability condition. In addition, mean and coefficient of variation of EMG increased and Fuzzy Entropy of EMG decreased when the difficulty in standing balance tasks increased. These results suggest that the higher postural sway complexity in stable condition, the greater capacity of the postural control system to adapt to the platform instability increases. In addition, changes in the complexity of EMG modulated by task difficulty do not necessarily reflect similar changes on postural sway.