The Use of Contextual Information for Anticipation of Badminton Shots in Different Expertise Levels.

Purpose: The current study investigated the use of contextual information for anticipation in badminton. Method: Participants were groups of elites (n = 26), competitive (n = 15) and novice players (n = 17) whose anticipation accuracy and reaction time were assessed using an ecologically valid badminton specific video-based occlusion test. Two conditions were presented, where either only kinematic information was available (Last Strokes condition, LS), or kinematic and contextual information were both available (Full Rally condition, FR). Results: Participants reacted slower in the FR condition, while no differences in accuracy were observed between the two conditions. Furthermore, all participants were better at side predictions than length, and elites outperformed novices in both side and length predictions. Among the elite group (which was split into adult elites, adult sub-elites & young elites), adult elite athletes showed faster responses for both the LS and FR conditions compared to their other elite counterparts who were much slower in both conditions. Conclusion: These results indicate that even at the highest level, anticipation performance can discriminate between groups of expert performers. In addition, the findings of this study indicate that the role of contextual information might not be as large as hypothesized, and further research is needed to clarify the role of contextual information toward anticipation.

Assessing the potential of the qualitative trajectory calculus to detect gait pathologies: a case study of children with developmental coordination disorder.

The Qualitative Trajectory Calculus (QTC) is a qualitative spatio-temporal calculus for describing interactions between moving point objects. So far, it remained unclear whether QTC is useful for describing subtle differences, such as between the movements of different parts of a human body. We tested the applicability of QTC to detect differences in the gait patterns of children with or without Developmental Coordination Disorder (DCD). We found that using a combination of three markers (i.e. ankle, toe and trochanter), QTC can achieve a high classification accuracy (i.e. 83.3%) of classifying subjects correctly to either the DCD group or the control group.

Anthropometry, Physical Fitness and Coordination of Young Figure Skaters of Different Levels.

The aim of the present study was to identify anthropometric, physical, coordinative and ice-skating specific characteristics that discriminate young elite ice skaters from non-elite skaters and their non-skating peers. 32 skaters aged 9-12 years old (11 elites and 21 non-elites) voluntarily participated in the study. They were submitted to 5 anthropometric, 7 physical, 3 coordination and 5 ice-skating specific tests. Reference values of a representative healthy non-skating sample were taken from the Flemish Sports Compass dataset. Figure skaters appeared to be predominantly average mature (93.8%), were lighter and leaner than the reference sample, and demonstrated better physical characteristics and motor coordination. There was no difference between the elite and non-elite group regarding maturity status and anthropometric or physical parameters. Still, elite skaters scored better than non-elites on the coordination tests jumping sideways and tended to do so on the moving sideways test. Profiles of figure skaters differ clearly from a reference population, while non-sport-specific motor coordination tests allow discrimination between elite and non-elite skaters. The relevance of these findings with respect to talent detection and identification in young ice skaters are discussed.

Relative age, biological maturation and anaerobic characteristics in elite youth soccer players.

Being relatively older and having an advanced biological maturation status have been associated with increased likelihood of selection in young elite soccer players. The aims of the study were to investigate the presence of a relative age effect (RAE) and the influence of birth quarter on anthropometry, biological maturity and anaerobic parameters in 374 elite Belgian youth soccer players. The sample was divided into 3 age groups, each subdivided into 4 birth quarters (BQ). Players had their APHV estimated and height, weight, SBJ, CMJ, sprint 5 and 30 m were assessed. Overall, more players were born in BQ1 (42.3%) compared with players born in BQ4 (13.7%). Further, MANCOVA revealed no differences in all parameters between the 4 BQ's, controlled for age and APHV. These results suggest that relatively youngest players can offset the RAE if they enter puberty earlier. Furthermore, the results demonstrated possible differences between BQ1 and BQ4, suggesting that caution is necessary when estimating differences between players because of large discrepancies between statistical and practical significance. These findings also show that coaches should develop realistic expectations of the physical abilities of younger players and these expectations should be made in the context of biological characteristics rather than chronological age-based standards.

The relative timing between eye and hand in rapid sequential pointing is affected by time pressure, but not by advance knowledge.

The present study examined the effect of timing constraints and advance knowledge on eye-hand coordination strategy in a sequential pointing task. Participants were required to point at two successively appearing targets on a screen while the inter-stimulus interval (ISI) and the trial order were manipulated, such that timing constraints were high (ISI = 300 ms) or low (ISI = 450 ms) and advance knowledge of the target location was present (fixed order) or absent (random order). Analysis of eye and finger onset and completion times per segment of the sequence indicated that oculo-manual behaviour was in general characterized by eye movements preceding the finger, as well as 'gaze anchoring' (i.e. eye fixation of the first target until completion of the finger movement towards that target). Advance knowledge of future target locations lead to shorter latency times of eye and hand, and smaller eye-hand lead times, which in combination resulted in shorter total movement times. There was, however, no effect of advance knowledge on the duration of gaze anchoring. In contrast, gaze anchoring did change as a function of the interval between successive stimuli and was shorter with a 300 ms ISI versus 450 ms ISI. Further correlation analysis provided some indication that shorter residual latency is associated with shorter pointing duration, without affecting accuracy. These results are consistent with a neural mechanism governing the coupling of eye and arm movements, which has been suggested to reside in the superior colliculus. The temporal coordination resulting from this coupling is a function of the time pressure on the visuo-manual system resulting from the appearance of external stimuli.

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.

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.

Visual contribution to walking in children with Developmental Coordination Disorder.

BACKGROUND: The motor co-ordination problems of children with Developmental Coordination Disorder (DCD) have been frequently associated with poor visuospatial processing. In order to extend these findings mainly based on fine motor experiments, the present study investigates the contribution of vision to the control of walking in children with DCD. METHODS: Children with DCD (n = 12) walked at their preferred speed on a straight, firm and uncluttered walkway in a condition with normal lighting and in a dark condition. Spatiotemporal gait variables were assessed by means of a three-dimensional ProReflex camera system and compared with the gait pattern of matched, typically developing (TD) children (n = 12). RESULTS: In normal lighting, the gait pattern of both groups was similar, with the exception of subtle differences in the temporal phasing, showing a slightly longer support phase in the children with DCD. In the dark, step frequency and step length were decreased in the children with DCD, resulting in a significantly slower walking velocity. In addition, the medio-lateral excursion of the centre of mass tended to increase in this group. In the TD children, adaptations to the spatiotemporal pattern remained absent. CONCLUSIONS: These results suggest that children with DCD are more dependent on global visual flow information than TD children for the maintenance of balance and the control of velocity during walking. This increased dependency on visual control might be associated with a poorly developed internal sensorimotor model.

Interest of the ordered subsets expectation maximization (OS-EM) algorithm in pinhole single-photon emission tomography reconstruction: a phantom study.

Pinhole single-photon emission tomography (SPET) has been proposed to improve the trade-off between sensitivity and resolution for small organs located in close proximity to the pinhole aperture. This technique is hampered by artefacts in the non-central slices. These artefacts are caused by truncation and by the fact that the pinhole SPET data collected in a circular orbit do not contain sufficient information for exact reconstruction. The ordered subsets expectation maximization (OS-EM) algorithm is a potential solution to these problems. In this study a three-dimensional OS-EM algorithm was implemented for data acquired on a single-head gamma camera equipped with a pinhole collimator (PH OS-EM). The aim of this study was to compare the PH OS-EM algorithm with the filtered back-projection algorithm of Feldkamp, Davis and Kress (FDK) and with the conventional parallel-hole geometry as a whole, using a line source phantom, Picker's thyroid phantom and a phantom mimicking the human cervical column. Correction for the angular dependency of the sensitivity in the pinhole geometry was based on a uniform flood acquisition. The projection data were shifted according to the measured centre of rotation. No correction was made for attenuation, scatter or distance-dependent camera resolution. The resolution measured with the line source phantom showed a significant improvement with PH OS-EM as compared with FDK, especially in the axial direction. Using Picker's thyroid phantom, one iteration with eight subsets was sufficient to obtain images with similar noise levels in uniform regions of interest to those obtained with the FDK algorithm. With these parameters the reconstruction time was 2.5 times longer than for the FDK method. Furthermore, there was a reduction in the artefacts caused by the circular orbit SPET acquisition. The images obtained from the phantom mimicking the human cervical column indicated that the improvement in image quality with PH OS-EM is relevant for future clinical use and that the improvements obtained using the OS-EM algorithm are more significant for the pinhole geometry than for the conventional parallel-hole geometry. We conclude that PH OS-EM is a practical and promising alternative for pinhole SPET reconstruction.

Three-dimensional multimodality medical image registration using a parameter accumulation approach.

A parameter accumulation method based on the Hough transformation is proposed to register three-dimensional (3-D) multimodality medical images. The estimation of registration parameters is decomposed into separate estimations of rotation, using directional vectors, and translation, using positional vectors. Similarly, the rotation parameters are decomposed into the rotation axis and angle, which are then estimated separately. This kind of decomposition reduces the parametric dimension and improves the computing efficiency which has been a major concern in implementing the Hough transformation. When 3-D rotation is involved, evaluating registration error is not straightforward. This paper introduces an equivalent error angle as a criterion to evaluate the performance of 3-D registration methods. Experimental results indicate that a least-squares fitting is superior to the parameter accumulation with data contaminated by additive noise only. When mismatched feature points (outliers) exist in the data set, however, the parameter accumulation approach is more accurate. The application of the proposed approach to the registration of 3-D PET and CT images is demonstrated.

Protocols for selection of cardiac radionuclide studies for use as a data base of normal studies and typical patterns of diseases. COST B2 Working Group II, in association with relevant working/task groups of the European Association of Nuclear Medicine and the European Society of Cardiology.

A data base of clinical studies is required for quality assurance of software used for analysis of radionuclide cardiac imaging procedures. Studies used must be rigorously validated in terms of both the clinical condition of the patient undergoing the procedure and the imaging protocol used. Selection protocols for the creation of a software phantom data base of normal studies and three typical patterns of cardiac disease--recent transmural myocardial infarction, isolated myocardial ischaemia and dilated cardiomyopathy--have been developed by the Cardiac Working Group of the European COST B2 project in association with the Cardiac Task Group of the European Association of Nuclear Medicine and the Working Group on Nuclear Cardiology of the European Society of Cardiology. These protocols include criteria for the interpretation of qualitative and quantitative non-radionuclide data. Compliance of the clinical data with the selection criteria will have to pass scrutiny by an international team for each study used as a software phantom. The radionuclide studies encompass stress and rest myocardial perfusion studies (planar and single photon emission tomography) using thallium-201 and technetium-99m methoxyisobutylisonitrile and rest gated blood pool studies. Methods for acquisition of data are defined for each type of study and for each individual study a portfolio of all clinical data is established. A pilot study is required to investigate the problems and logistics of distributing clinical radionuclide studies between a range of computers and institutes, and to ascertain the procedures necessary for analytical comparison of the results obtained.

A file format for the exchange of nuclear medicine image data: a specification of Interfile version 3.3.

Working Group 1 of the European project COST-B2 on quality assurance of nuclear medicine software has been concerned with the development of an appropriate mechanism for the transfer of nuclear medicine image data files between computer systems from different vendors. To this end a protocol based upon Report No. 10 of the American Association of Physicists in Medicine (AAPM) [1] was adopted. A previous publication [2] gave a specification (V3.2) for an intermediate file format with a list of key-value pairs for the header data associated with nuclear medicine image data files. This paper presents a revised specification for the intermediate file format and associated keys, now called V3.3, which has evolved from the experience in using the earlier version. It is hoped that the modifications proposed will improve the definition and usability of the file format as given in the earlier version.

MR imaging of blood vessels using three-dimensional reconstruction: methodology.

Multisection, dual-echo magnetic resonance (MR) transaxial images of blood vessels contain both anatomic and qualitative information about flow. Even so, the images are produced as a series of two-dimensional tomographic sections from which full visualization of connected structures is difficult. A computer algorithm was developed that automatically detects flowing blood based on pixel intensity and calculated T2 and provides reconstructed views of vessels while analyzing and displaying flow characteristics. Images of abdominal vessels, aortic aneurysms, and the heart were encoded by flow and color to demonstrate depth. In addition, these data were reconstructed to derive a more accurate assessment of patency. With this technique, transaxial images can be used to analyze flow patterns, determine patent areas, and visualize all levels of vessels in a single image.

Radionuclide evaluation of left ventricular synergic pumping efficiency during acute myocardial infarction.

The clinical value of an index of left ventricular synergic pumping efficiency (EFF) was evaluated in 50 patients with uncomplicated myocardial infarction in which radionuclide ventriculography was performed within 72 h of the onset of the infarction and between 7 and 13 days post infarction. EFF was defined as the ratio of global left ventricular stroke volume to the magnitude of all intraventricular blood pool variations measured on a pixel by pixel basis. EFF correlated better with a subjectively evaluated wall motion index (r = 0.84) than did the ejection fraction (EF) measurements (r = 0.69). In all patients, but most significantly in patients with inferoposterior infarctions, EFF measurements in the acute phase were a better predictor of the predischarge ventricular performance than the EF measurements. The left ventricular EFF is a reliable parameter to quantitate the effect of regional wall motion disturbances on global ventricular function in a standardized manner.

The adaptation of the human thyroid gland to a physiological regimen of iodide intake: evidence for a transitory inhibition of thyroid hormone secretion modulated by the intrathyroidal iodine stores.

The effects of iodide on thyroid function were so far only studied after administration of pharmacological or small continuous doses. We were interested to know how the human thyroid gland would react to a more physiological situation: small doses taken in intermittently. Ten normal male volunteers were given weekly doses of iodide: 1 mg for the first 6 weeks and 2 mg afterwards for another 6 weeks period. Intrathyroidal iodine stores were evaluated by the X-Ray-Fluorescence method. The following thyroid parameters were estimated during the 3 months period: total thyroxine, total triiodothyronine, free thyroxine, free triiodothyronine, reverse triiodothyronine, plasma inorganic iodide, thyroid stimulating hormone and thyrotropin-releasing hormone tests. The following observations were made: i) a steady increase of intrathyroidal iodine (p less than 0.01); ii) no changes in free thyroxine, free triiodothyronine, thyroid stimulating hormone, thyrotropin-releasing hormone test or plasma inorganic iodide. iii) a decrease of total thyroxine (and total triiodothyronine) with a nadir at about 3 weeks and a spontaneous rise afterwards; repetition of this phenomenon by doubling the dose of iodide. It is concluded that 1 mg or 2 mg iodide a week does not inhibit incorporation into the normal human thyroid gland and suggested that these physiological doses of iodide cause a transitory inhibition of thyroxine secretion, representing a form of autoregulation of the thyroid cell, since it was modulated by the intrathyroidal iodine stores and no evidence of pituitary mediation could be evidenced in the experimental protocol.

Seasonal variation of stable intrathyroidal iodine in nontoxic goiter disclosed by x-ray fluorescence.

The intrathyroidal stable iodine (ITI) determined in 776 patients chosen at random. Ninety % of these patients presented with nontoxic goiter. Curve-filtering analysis techniques showed a seasonal variation in ITI: an acrophase was found in April/May, a nadir in September/October. The possible relationship of this seasonal variation with the intake of iodine or alimentary antithyroid substances are discussed, as well as possible relationship with variation in chronic TSH stimulation related to ambient temperature.

Atrophic autoimmune thyroiditis: relationship between the clinical state and intrathyroidal iodine as measured in vivo in man.

The intrathyroidal iodine (ITI) was measured by means of the x-ray fluorescence method in 58 patients suffering from atrophic autoimmune thyroiditis (AAT). They were divided into 4 groups according to their basal T4, basal TSH, and the peak TSH response after TRH administration. Forty-eight normal subjects served as controls. A progressive fall of ITI was found, with less ITI in the first grade AAT patients as compared to the controls. A negative correlation between basal TSH and ITI could be shown. These data support the concept of a graded evolution of AAT, linking the clinical state to the ITI. The results also suggest that, with the hemagglutination techniques used for the determination of antithyroglobulin antibodies and antithyroid microsomal antibodies, positively at a dilution of 1:25 and 1:100, respectively, should be regraded as significant.