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Jumping Impairs Visual Feedback Control of Body Position

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Zemková E., Hamar D.

Human Movement

2011

vol. 12

issue 3

248-253

Purpose. The aim of this study was to evaluate the effects of maximal rebound jumping on sensorimotor tasks that required visual feedback control in positioning the body. Methods. A group of 14 university students (age 23.7 ± 2.6 y, height 178.6 ± 9.2 cm, and weight 70.6 ± 11.4 kg) had to hit a target that randomly appeared on one side of a screen by horizontally shifting their centre of mass (COM) in the appropriate direction prior to (as a baseline) and after six 60-second maximal jump exercises. Each response test consisted of 60 targets. The time, distance, and the velocity of the centre of pressure (COP) trajectory between the stimulus's appearance and its hit, by visually-guiding the COM movement on the screen, were registered by means of a FiTRO Sway Check system using a dynamometric platform. During the sets of jumps, the power of the concentric phase of take off was registered using a FiTRO Jumper recorder. Results. Results found that after each set of jumping (of around 110 jumps per set), mean response time significantly (p ≤ 0.05) increased from an initial value of 1616 ± 506 ms to 1825 ± 562 ms till the 4th set, with no further increase towards the 6th set. Similarly, the mean distance of COP covered during the response time increased significantly (p ≤ 0.05) from a pre-exercise value of 0.449 ± 0.298 m to 0.550 ± 0.295 m after the 4th set which then plateaued towards the 6th set. However, no significant changes in mean COP velocity were detected. Conclusion. Rebound jumping negatively affected the visual feedback control in positioning the body. However, after the proprioceptive functions deteriorated to a certain level, there was no further impairment on sensorimotor parameters.

Biomechanical Analysis of Defensive Cutting Actions During Game Situations: Six Cases in Collegiate Soccer Competitions

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Sasaki S., Koga H., Krosshaug T., Kaneko S., Fukubayashi T.

Journal of Human Kinetics

2015

vol. 46

issue 1

9-18

The strengths of interpersonal dyads formed by the attacker and defender in one-on-one situations are crucial for performance in team ball sports such as soccer. The purpose of this study was to analyze the kinematics of one-on-one defensive movements in soccer competitions, and determine the relationships between lower limb kinematics and the center of mass translation during cutting actions. Six defensive scenes in which a player was responding to an offender’s dribble attack were selected for analysis. To reconstruct the three-dimensional kinematics of the players, we used a photogrammetric model-based image-matching technique. The hip and knee kinematics were calculated from the matched skeleton model. In addition, the center of mass height was expressed as a ratio of each participant’s body height. The relationships between the center of mass height and the kinematics were determined by the Pearson’s product-moment correlation coefficient. The normalized center of mass height at initial contact was correlated with the vertical center of mass displacement (r = 0.832, p = 0.040) and hip flexion angle at initial contact (r = −0.823, p = 0.044). This suggests that the lower center of mass at initial contact is an important factor to reduce the downwards vertical center of mass translation during defensive cutting actions, and that this is executed primarily through hip flexion. It is therefore recommended that players land with an adequately flexed hip at initial contact during one-on-one cutting actions to minimize the vertical center of mass excursion.

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1 Sasaki S.

1 Zemková E.

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Jumping Impairs Visual Feedback Control of Body Position

Biomechanical Analysis of Defensive Cutting Actions During Game Situations: Six Cases in Collegiate Soccer Competitions