G.J.P. Savelsbergh

The relation of unimanual and bimanual reaching to crossing the midline.

The present study assessed the development of reaching for objects positioned in front of the contralateral shoulder. In particular, it examined how the development of crossing the midline is related to the development of bimanual reaching. Twenty infants were observed longitudinally at 12, 18, and 26 weeks of age while reaching for two balls (3 cm and 8 cm in diameter) located at three positions (ispsilateral, midline, and contralateral). The reaches were analyzed from video recordings. With age, the infants increasingly adapted the number of hands used to the size of the object. The number of reaches crossing the body midline increased with age. Furthermore, the majority of the midline crossings were part of two-handed reaches for the large ball and occurred at or after onset of bimanual reaching. Together, these findings strongly suggest that the development of crossing the body midline emerges in the context of bimanual reaching. It was concluded that the need to grasp a large ball positioned contralaterally with two hands induces midline crossing. Hence, the development of midline crossings is not exclusively dependent on organismic constraints (e.g., the maturation of hemispheric connections), but rather on their interaction with environmental constraints (e.g., object size).

Balance problems during obstacle crossing in children with Developmental Coordination Disorder

The present study investigated the visuomotor and balance limitations during obstacle crossing in typically developing (TD) children and those with Developmental Coordination Disorder (DCD) (7-9 years old; N=12 per group). Spatiotemporal gait parameters as well as range and velocity of the centre of mass (COM) were determined in three conditions: overground walking at a self-selected speed, crossing a low obstacle and crossing a high obstacle (5% or 30% of the leg length, respectively). Both groups walked more slowly during obstacle crossing than walking over level ground. In addition, both groups exhibited a significant decrease in the spatial variability of their foot placements as they approached the obstacle, which was then negotiated with a similar strategy. There were no differences in approach distance, length of lead and trail step, or lead and trail foot elevation. Compared to walking over level ground, obstacle crossing led to a longer swing phase of the lead and trail foot and increased maximal medio-lateral COM velocity. In children with DCD, however, medio-lateral COM velocity was higher and accompanied by significantly greater medio-lateral COM amplitude. In conclusion, the results indicate that while TD-children and those with DCD exhibit satisfactory anticipatory control and adequate visual guidance, the latter group have a reduced ability to control the momentum of the COM when crossing obstacles that impose increased balance demands.

Timing a one-handed catch. I. Effects of telestereoscopic viewing

Abstract The aim of this study was to examine the role of binocular and monocular information sources in specifying time-to-contact. More specifically, it was investigated whether the timing of the one-handed catch is consistent with a binocular tau-function strategy. Subjects (n=8) were required to time their grasp to catch a ball approaching with a constant spatial trajectory. The ball approached at three different constant velocities (1.5, 2.0 and 2.5 m/s). Vergence and disparity were manipulated through subjects wearing a telestereoscope to increase the effective interocular separation, under both binocular and monocular viewing. Subjects performed 24 trials in each of the four conditions. Subjects’ started the opening of the hand earlier in the binocular telestereoscope condition when a ball approached with velocity of 1.5 m/s. They then closed the hand earlier in the binocular telestereoscope condition at all ball approach velocities. There were no effects of telestereoscope on the timing of hand opening and closing under monocular viewing. This finding suggests the use of the binocular information in timing the grasp. However, there were effects of approach velocity under all conditions of monocular and binocular viewing. Subjects’ closed the hand earlier as a function of increasing approach velocity. Together, the effects of the telestereoscope and approach velocity indicate that timing of the one-handed catch is not consistent with the use of a binocular ”tau-function” variable. Rather, it is concluded that multiple sources of monocular and binocular information contribute to the regulation of timing.

Visual guidance during an interception task in children with Spastic Hemiparetic Cerebral Palsy

The aims of the study are to determine the presence of adjustments in walking behaviour of children with Spastic Hemiparetic Cerebral Palsy (SHCP) during the interception of a moving ball and, whether the angle between the ball and the participant is kept constant. This would support the use of the so-called bearing angle (BA) strategy in interception of the object. Children with left hemisphere damage intercepted a ball from a conveyor belt at three different velocities, from a frontal or lateral orientation and with their impaired or less-impaired hand. The participants walked from a distance of 4m perpendicularly to the belt. Children seemed to have less successful trials when grasping with the impaired hand. The results showed that the walking velocity was adjusted to the ball velocity. When they grasped with the impaired hand, children initially moved faster to the interception point, while closer to the belt significant slower. The BA showed less variation over the trajectory when the children grasped with their less-impaired hand or when the ball velocity increased. It was concluded that children with SHCP were able to take their impairment into account as indicated by adjustments in walking behaviour. However, these adjustments in walking velocity were not sufficient to compensate totally for the limited reaching ability in the impaired hand. As a result of these adjustments, the amount of variation from the constant BA seemed to deviate more from typically developing children when grasping with impaired hand than when grasping with less-impaired hand.

Visual guidance of interceptive actions in children with spastic unilateral cerebral palsy is influenced by the side of the lesion

Purpose. To determine the type of visual information used by children with spastic unilateral cerebral palsy (SUCP) in order to intercept a ball and to verify whether this information was dependent on the side of the lesion. More specifically, it was examined whether the interception was controlled on the basis of a time or a distance strategy, initiating the catch when the ball is at a fixed time interval or at a fixed distance from the point of interception. Methods. Three groups of children were included. Children with either a left sided (LHL) or a right sided lesion (RHL) and children without a lesion [typically developing (TD)] intercepted a ball from a conveyor belt. In order to intercept the ball successfully they had to walk and to reach for the ball at the interception point 4 m away. Results. Children with LHL had a longer decision time and started their reach movement earlier. In 56% of the children with LHL a distance strategy was observed, while in the TD and the children with RHL predominantly a time strategy was found. Conclusions. The side of the lesion influences the visual information used to initiate interceptive actions.

'Keeping the eye on the ball': the legacy of John Whiting (1929-2001) in sport science

`Keep your eye on the ball’ is the statement that made John Whiting famous in the world of physical education during the 1960s and early 1970s. It re ̄ ects very sound advice for any academic interested in teaching and research in the areas of movement coordination and control, skill acquisition and motor development. John Whiting passed away on 7 October 2001. Although his achievements in physical education, psychology and human movement science are well known and well documented, it is important to recognize his legacy in sport science; we feel that the Journal of Sport Sciences is an appropriate outlet to do so. Perhaps his most signi® cant contribution to higher education in the UK was to put physical education onto a more scienti® c footing through the establishment of the ® rst postgraduate empirical research programme on motor behaviour, including specialist taught Masters provision. The innovative nature of his thinking becomes clear when one considers that this programme was a precursor to the development of undergraduate sports science provision in the UK almost a decade later. Between the early 1960s and the late 1970s, his research group at the Department of Physical Education at Leeds University produced eight doctorates (including his own), four books and 25 peer-reviewed scienti® c research articles. These achievements were outstanding in an age before desktop computers and laptops. They were achieved against a backdrop of low ® nancial and technical support as well as a lack of understanding of the nature of experimental work in physical education by the university authorities at that time (for an interesting personal account, see Whiting, 1991). His seminal book Acquiring Ball Skill, which appeared in 1969, contains a detailed theoretical and empirical account of the performance and acquisition of ball skills; it was a bestseller in English and has been translated into French and Japanese. In this tribute to his legacy, we will comment on John Whiting’ s impact and contribution to the sport sciences, which can be divided into two main areas of research: dynamic interceptive actions and learning studies.