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Ben Serrien, Maggy Goossens and Jean-Pierre Baeyens

Performing a volleyball spike movement requires a great amount of coordination between the different degrees of freedom (DOF) throughout the entire chain of motion in a specific sequence. In the shoulder alone, a complex sequence of muscle activity is observed during the windup, cocking

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Carlo Di Brina, Roberto Averna, Paola Rampoldi, Serena Rossetti and Roberta Penge

as visual constructive and psychomotor coordination impairments, as a co-occurrence of a developmental coordination disorder (DCD; Jongmans, Smits-Engelsmann, & Schoemaker, 2003 ; Kaplan, Wilson, Dewey, & Crawford, 1998 ). The association of LD with a motor coordination impairment is quite common

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Danielle N. Jarvis, Jo Armour Smith and Kornelia Kulig

Variability, or how a task changes across trials, may reveal differences between athletes of differing skill levels. The purpose of this study was to examine trunk and lower extremity (LE) single joint kinematic variability and intersegmental coordination variability in dancers and nondancers during bipedal vertical dance jumps (sautés). Twenty healthy females, 10 with no formal dance training and 10 professional dancers, performed 20 consecutive sautés. Single joint kinematic variability was assessed using mean standard deviation of angular displacement, and intersegmental coordination variability was assessed using angular deviation of the coupling angle between segments. Within the context of the standard error of measure, there was no difference in single joint kinematic variability between dancers and nondancers. Intersegmental coordination variability in the trunk was higher than variability in LE couplings for both groups. Dancers had lower intersegmental coordination variability than nondancers for LE sagittal, frontal, and transverse plane couplings, and sagittal plane trunk couplings. Trunk adjustments may be important for successful performance, but lower intersegmental coordination variability in expert dancers indicates a higher level of control. Trunk coordination and postural control may be important factors to investigate in skilled athletes.

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David R. Collins, Hyeongsaeng Park and Michael T. Turvey

Von Holst (1939/1973) parsed intersegmental coordination into relative and absolute to distinguish moderate and extreme forms. Kelso and DeGuzman (1992) discussed an interpretation of relative coordination in terms of the chaotic phenomenon of intermittency. The data of concern (DeGuzman & Kelso, 1991) do not, however, exclude a stochastic interpretation, which is detailed here following earlier suggestions. The key difference is modeling relative coordination by stochastic variability about weak attractors rather than by deterministic variability about remnants of attractors (”ghost attractors”). The intermittency interpretation is not robust in the presence of noise and, therefore, is not well disposed to account for uncertainty in detailing a model of behavioral data or its parameters. In contrast, the stochastic interpretation is based upon an approximation of unknown underlying processes in the form of Gaussian white noise. A stochastic method for estimating model parameters from a stationary probability distribution and a mean first passage time is illustrated using experimental and simulated data.

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Sukhvinder S. Obhi

Using more than one limb to perform functional, goal-directed actions is arguably one of the most important abilities that human beings possess. In many everyday tasks, the hands, in particular, must be used to accomplish all manner of goals. From buttoning a shirt to opening a jam jar and driving to work, good bimanual coordination is of great utility. In addition to the tasks mentioned above, there are also other tasks involving the functional use of more than one limb, including walking or cycling and typing a report. With a little thought, it becomes apparent that there is at least one important difference between these categories of coordination tasks. On one hand, in some tasks the effectors must perform markedly different motor outputs that are bound together in some functionally defined and usually object-oriented manner (e.g., buttoning a shirt) yet, in others, the effectors produce very similar motor outputs but in a specific temporal order, which may or may not repeat itself periodically (e.g., walking and cycling compared to typing or drumming). In this short article, I will argue that the second category of coordination task and, in particular, cyclical coordination, has been studied extensively and, at least at the level of behavior, is relatively well understood. In contrast the former category of bimanual task is seldom studied and, even at the descriptive level, is rather poorly understood. One of the reasons for this may be the complexity of such tasks and the technical difficulties involved in attempting to study them. By highlighting some key studies, I hope to illustrate that such tasks can be fruitfully studied in the laboratory. Last, since the neural control processes underlying both classes of coordination task are not yet well known, I aim to draw attention to the potential value of the interventional technique of Transcranial Magnetic Stimulation (TMS) as a tool for investigating the functions of brain regions contributing to bimanual coordination.

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C.C.A.M. Gielen

The target article by Prilutsky gives an excellent overview of the predictions of the Crowninshield and Brand model and about the relevant literature about muscle coordination. However, we do not agree with the claim that the Crowninshield and Brand model can explain the coordination between one-joint and two-joint muscles. In this commentary we will make three claims: (a) The Crowninshield and Brand model cannot explain all aspects of muscle coordination, (b) there is good experimental evidence that different constraints and models may be necessary to explain muscle coordination in different motor tasks, and (c) the reason for the lack of quantitative fits between predictions about muscle force and experimental data is that it is hard to measure muscle force in man. As a compromise one has to rely on EMG activity as a measure of muscle force. Because of the complex relationship between EMG and muscle force, a quantitative test of models is difficult.

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Cameron O’Beirne, Dawne Larkin and Tim Cable

Generally, children with coordination problems lack fitness and muscular strength. This study was designed to identify whether these children differed from age-matched controls on measures of anaerobic performance. Twenty-four boys who were poorly coordinated, from three age groups, 7, 8, and 9 years, were compared to 24 coordinated controls (N = 48). The McCarron (1982) Assessment of Neuromuscular Development (MAND) was used to confirm levels of coordination. Anaerobic performance was estimated with the Wingate Anaerobic Test (WAnT) and a 50-m run. The poorly coordinated group’s performance on the WAnT was significantly lower than the performance of the controls for measures of peak power normalized for body weight, absolute and normalized mean power, and the fatigue index. The subjects who were poorly coordinated were also significantly slower performing the 50-m sprint. There was a significant relationship between power measured on the WAnT and coordination measured by the MAND gross motor score. For this population, coordination problems were considered among the factors that may interfere with the measurement of anaerobic performance.

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Dana Maslovat, Shannon S.D. Bredin, Romeo Chua and Ian M. Franks

A major component of a dynamical paradigm involves a “scanning” procedure in an attempt to determine an individual’s intrinsic coordination tendencies before learning, as well as subsequent changes in the coordination landscape after practice. The purpose of the present study was to evaluate two methods of the scanning procedure. Scans were performed before and after 75 trials of a 90° bimanual-coordination pattern and were compared with early and late acquisition trials. Four groups of participants performed scanning and acquisition trials using a combination of either concurrent visual feedback in the form of Lissajous figures, paced by an auditory metronome, or visual metronomes in the form of flashing stimuli. Analyses revealed that all groups improved performance of the 90° pattern with practice. As predicted by the theory of practice specificity, scanning via the same method as acquisition appears to be valid. Scanning via Lissajous figures when the acquisition procedure was flashing squares was also found to be valid, but not the opposite condition. Reasons for this unidirectional transfer are given with these results suggesting that the sensitivity of a given scanning method might be influenced by the method of acquiring the coordination pattern.

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Annlaug Flem Maeland

This study focuses on identification of children with motor coordination problems and investigates whether the incidence of children with such problems in a normal school setting in Norway is comparable to that found in other countries using the same tests and criteria. The study also examines whether there would be any agreement between two motor tests, the Test of Motor Proficiency (TMP) and the Test of Motor Impairment (TOMI), and teachers’ judgment in identifying clumsiness among 360 children 10 years of age. The results showed that while the three different assessment methods identified about the same number of children with such problems (5-5.6%), each measure identified a somewhat different set of children. The lack of agreement demonstrates the difficulty in assessing subtle motor coordination problems or clumsiness.

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David P. Black, Michael A. Riley and Christopher K. McCord

The authors conducted two experiments that served as a test bed for applying the recently developed uncontrolled manifold (UCM) approach to rhythmic motor coordination, which has been extensively investigated from a coordination dynamics perspective. The results of two experiments, one investigating withinperson and one investigating between-persons rhythmic movement coordination, identified synergistic behaviors in both of those types of coordination. Stronger synergies were identified for in-phase than antiphase coordination, at the endpoints of the movement cycles compared with the midpoints, for movement frequencies closer to the intrinsic frequency of the coordinated limbs, and for within-person coordination. Frequency detuning did not weaken the strength of interlimb rhythmic coordination synergies. The results suggest the synergistic behavior captured by the UCM analysis may be identifiable with the strength of coupling between the coordinated limbs. The UCM analysis appears to distinguish coordination parameters that affect coupling strength from parameters that weaken coordination attractors.