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  • Author: Geert J.P. Savelsbergh x
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Geert J.P. Savelsbergh and J. Bernard Netelenbos

Spatial information for the execution of motor behavior is acquired by orienting eye and head movements. This information can be found in our direct field of view as well as outside this field. Auditory information is especially helpful in directing our attention to information outside our initial visual field of view. Two topics on the effect of an auditory loss are discussed. Experimental evidence is provided which shows that deaf children have problems in orienting to visual stimuli situated outside their field of view. An overview is given from several studies in which the eye and head movements of deaf children are analyzed. Second, it is suggested that specific visual localization problems are partly responsible for deaf children’s characteristic lag in motor development. The latter is illustrated in two studies involving the gross motor task of ball catching.

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Geert J.P. Savelsbergh and John Van der Kamp

The Smeets and Brenner view on grasping is simple: grasping is in fact pointing. In our comments we examine the model beyond the reach-to-grasp task namely, by grasping (without reaching) of moving objects and eating. The model fits the data of both tasks. Although generalization of a model to different tasks usually strengthens its acceptance, in the present case it reveals its shortcomings, namely, both tasks include a clear grasping component that is hard to accept as pointing.

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Annieck X.C. Ricken, Simon J. Bennett and Geert J.P. Savelsbergh

Coordination of reaching with the impaired and non-impaired arm in 10 children with spastic hemiparetic cerebral palsy (SHCP) was examined in a stationary ball and moving ball context. Kinematic data on trunk, arm, and wrist movements, and coordination patterns between joint angles of elbow, shoulder, and trunk, were analyzed to determine how reaching was influenced by impairment and object motion. Results showed longer deceleration time and movement time and greater trunk contribution following decreased elbow and shoulder excursion when reaching with the impaired arm compared to the non-impaired arm. The coordination of joint angle pairs showed little linearity for the impaired arm, indicating more segmented movements of shoulder and elbow. It was also found that coordination patterns between elbow, shoulder, and trunk displayed less similarity when reaching with the impaired arm compared to the non-impaired arm in both stationary and moving ball conditions. Regardless of the timing constraints, children with SHCP could make successful interceptions using the impaired arm, indicating that they coordinated and controlled the degrees of freedom within their own functional possibilities.

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Pieter Tijtgat, Jos Vanrenterghem, Simon J. Bennett, Dirk De Clercq, Geert J.P. Savelsbergh and Matthieu Lenoir

The purpose of this study was to investigate postural adjustments in one-handed ball catching. Specifically, the functional role of anticipatory postural adjustments (APA) during the initial arm raising and subsequent postural adjustments (SPA) for equilibrium control and ball-hand impact were scrutinized. Full-body kinematics and kinetics allowed an analysis of the mechanical consequences of raising up the arm and preparing for ball-hand impact. APA for catching were suggested to be for segment stabilization. SPA had a functional role for equilibrium control by an inverted pendulum mechanism but were also involved in preparing for the impact of the ball on the hand, which was illustrated by an increased postural response at the end of the movement. These results were compared with raising up the arm in a well-studied reaction-time task, for which an additional counter rotation equilibrium mechanism was observed. Together, our findings demonstrate that postural adjustments should be investigated in relation to their specific functional task constraints, rather than generalizing the functional role of these postural adjustments over different tasks.

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Liesbeth I.N. Mazyn, Gilles Montagne, Geert J.P. Savelsbergh and Matthieu Lenoir

In the present study, the limits of human catching behavior were challenged to investigate quantitative and qualitative adaptations of the catching movement when performing under varying ball speeds, implying minor as well as severe temporal constraints. Nine male participants caught balls approaching at speeds ranging from 8.5 to 19.7 m/s with their preferred hand. Although a decrease in catching performance was undeniable, several quantitative adaptations provided the catcher with extra time and allowed to compensate the decrease in spatial accuracy with increasing speed. More importantly, changes in the coordination between hand, elbow, and shoulder emerged with increasing movement velocity. More demanding temporal constraints lead to a shift from relatively independent activity of each joint towards a mode in which several joints act as one unit. This reorganization of the coordination pattern of the catch is discussed in the context of Bernstein’s degrees of freedom problem.

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Geert J.P. Savelsbergh, John van der Kamp and Walter E. Davis

Twenty-one children with Down syndrome (DS) and 20 without disability, ages 3 to 11 years, completed the experiment in which they were asked to grasp and lift cardboard cubes of different sizes (2.2 to 16.2 cm in width). Three conditions were used: (a) increasing the size from the smallest to the largest cube, (b) decreasing the size from the largest to the smallest, and (c) a random order of sizes. Children with DS were found to have smaller hand sizes in comparison to age-matched children without DS. In addition, the shift from one-handed to two-handed grasping appeared at a smaller cube size for children with DS than for children without DS. However, when the dimensionless ratio between object size and hand size was considered, the differences between groups disappeared, indicating that the differences in grasping patterns between children with and without DS can be attributed to differences in body size.

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Martina Navarro, Nelson Miyamoto, John van der Kamp, Edgard Morya, Ronald Ranvaud and Geert J.P. Savelsbergh

We investigated the effects of high pressure on the point of no return or the minimum time required for a kicker to respond to the goalkeeper’s dive in a simulated penalty kick task. The goalkeeper moved to one side with different times available for the participants to direct the ball to the opposite side in low-pressure (acoustically isolated laboratory) and high-pressure situations (with a participative audience). One group of participants showed a significant lengthening of the point of no return under high pressure. With less time available, performance was at chance level. Unexpectedly, in a second group of participants, high pressure caused a qualitative change in which for short times available participants were inclined to aim in the direction of the goalkeeper’s move. The distinct effects of high pressure are discussed within attentional control theory to reflect a decreasing efficiency of the goal-driven attentional system, slowing down performance, and a decreasing effectiveness in inhibiting stimulus-driven behavior.

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Wim H. van Lier, John van der Kamp and Geert J.P. Savelsbergh

We assessed how golfers cope with the commonly observed systematic overshoot errors in the perception of the direction between the ball and the hole. Experiments 1 and 2, in which participants were required to rotate a pointer such that it pointed to the center of the hole, showed that errors in perceived direction (in degrees of deviation from the perfect aiming line) are destroyed when the head is constrained to move within a plane perpendicular to the green. Experiment 3 compared the errors in perceived direction and putting errors of novice and skilled players. Unlike the perceived direction, putting accuracy (in degrees of deviation from the perfect aiming line) was not affected by head position. Novices did show a rightward putting error, while skilled players did not. We argue that the skill-related differences in putting accuracy reflect a process of recalibration. Implications for aiming in golf are discussed.

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Max G. Feltham, Annick Ledebt, Simon J. Bennett, Frederik J.A. Deconinck, Martine H.G. Verheul and Geert J.P. Savelsbergh

The study examined symmetrical bimanual coordination of children with spastic hemiparetic cerebral palsy (SHCP) and a typically developing (TD) control group under conditions of visual feedback created by placing a glass screen, opaque screen or a mirror (“mirror box”) between the arms. The “mirror box” creates a visual illusion, which gives rise to a visual perception of a zero lag, symmetric movement between the two arms. Children with SHCP exhibited a similar mean coordination pattern as the TD control group, but had greater movement variability between the arms. Furthermore, movement variability in children with SHCP was significantly greater in the screen condition compared with the glass and mirror condition, which were similar to each other. The effects of the availability of visual feedback in individuals with hemiparesis are discussed with reference to central and peripheral mechanisms.

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Frederik J. A. Deconinck, Dirk De Clercq, Geert J. P. Savelsbergh, Rudy Van Coster, Ann Oostra, Griet Dewitte and Matthieu Lenoir

In the present study the walking pattern of 10 children with developmental coordination disorder (DCD) was investigated and compared to that of 10 typically developing, matched control children. All children walked at a similar velocity that was scaled to the length of the leg on a motor-driven treadmill. Three-dimensional kinematics were recorded with a motion capture digital camera system. The spatiotemporal parameters of the gait pattern revealed that children with DCD walked with shorter steps and at a higher frequency than the typically developing children. In addition, the children with DCD exhibited a body configuration that demonstrated increased trunk inclination during the entire gait cycle and enhanced during the entire gait cycle. At toe-off a less pronounced plantar flexion of the ankle was observed in children with DCD. In conclusion, it appeared that children with DCD make adaptations to their gait pattern on a treadmill to compensate for problems with neuromuscular and/or balance control. These adaptations seem to result in a safer walking strategy where the compromise between equilibrium and propulsion is different compared to typically developing children.