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Betteco J. de Boer, C. (Lieke) E. Peper and Peter J. Beek

Developmental changes in bimanual coordination were examined in four age groups: 6/7, 10/11, 14/15 years, and young adults. Temporal coupling was assessed through the stabilizing contributions of interlimb interactions related to planning, error correction, and reflexes during rhythmic wrist movements, by comparing various unimanual and bimanual tasks involving passive and active movements. Spatial coupling was assessed via bimanual line-circle drawing. With increasing age, temporal stability improved. Relative contributions of planning and reflex interactions to the achieved stability did not change, whereas error correction improved. In-phase and antiphase coordination developed at similar rates; implications of this result were discussed in terms of mirror-activity inhibition. Overall spatial drawing performance (circularity, variability, smoothness) improved with age, and spatial interference was smaller in adults than children. Whereas temporal coupling increased from 6/7 years to adulthood, spatial coupling changed mainly after 14/15 years. This difference in the development of temporal and spatial coupling corresponds to the anterior-posterior direction of corpus callosum myelination as reported in the literature.

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Leanna Ferrand and Slobodan Jaric

The purpose of this study was to explore the effects of handedness on coordination of grip (G) and load (L) forces in static bimanual manipulation tasks. Participants (N = 10) exerted various L profiles against an externally fixed hand-held device based on presumably open-loop and closed-loop neural control mechanisms, (i.e., mediated and not mediated, respectively, by sensory feedback). Average G/L ratio and the coupling of G and L (i.e., stability of the G/L ratio and correlation between G and L) were separately assessed in each hand. The results revealed a lower average G/L ratio in the non-dominant hand suggesting a more economical grip, while the indices of G and L coupling were similar in two hands. The dominant and non-dominant hand failed to reveal relative advantages in the tasks predominantly based on open- and closed-loop control mechanisms, respectively. We conclude that, due to the static nature of the tested tasks, the particular advantage of the non-dominant hand in G and L coordination could be in line with the recently proposed specialization of the non-dominant limb for control of position. However, the overall results are not in line with classic views of the prevailing open- closed-loop neural mechanisms in the control of the dominant and nondominant limb, respectively.

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Ronald C. Marteniuk and Christopher P. Bertram

The present paper reviews a series of prehension experiments recently conducted at Simon Fraser University's Human Motor Systems Laboratory, and attempts to place them into the larger context of multi-segmental control theory. Two related lines of experiments are reported: (a) experiments involving prehension during walking, and (b) experiments involving trunk-assisted reaching. Three-dimensional analyses of movements were performed via both world-and body-centered coordinates. Our results are supportive of the idea that both types of tasks are carried out using task-specific synergies. Furthermore, we assert that the actions of these synergies are comprised of variable contributions of different movement systems and result in smooth, world-centered end-point trajectories. We show evidence that this “motor equivalence” is the result of increasing the complexity of a given task. Finally, the implications of the present findings on prevailing motor control theory are discussed in terms of the theoretical mechanisms underlying the coordination of the transport and grasp components of prehension.

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João Ribeiro, Argyris G. Toubekis, Pedro Figueiredo, Kelly de Jesus, Huub M. Toussaint, Francisco Alves, João P. Vilas-Boas and Ricardo J. Fernandes

Purpose:

To conduct a biophysical analysis of the factors associated with front-crawl performance at moderate and severe swimming intensities, represented by anaerobic-threshold (vAnT) and maximal-oxygen-uptake (vV̇O2max) velocities.

Methods:

Ten high-level swimmers performed 2 intermittent incremental tests of 7 × 200 and 12 × 25 m (through a system of underwater push-off pads) to assess vAnT, and vV̇O2max, and power output. The 1st protocol was videotaped (3D reconstruction) for kinematic analysis to assess stroke frequency (SF), stroke length (SL), propelling efficiency (η P), and index of coordination (IdC). V̇O2 was measured and capillary blood samples (lactate concentrations) were collected, enabling computation of metabolic power. The 2nd protocol allowed calculating mechanical power and performance efficiency from the ratio of mechanical to metabolic power.

Results:

Neither vAnT nor vV̇O2max was explained by SF (0.56 ± 0.06 vs 0.68 ± 0.06 Hz), SL (2.29 ± 0.21 vs 2.06 ± 0.20 m), η P (0.38 ± 0.02 vs 0.36± 0.03), IdC (–12.14 ± 5.24 vs –9.61 ± 5.49), or metabolic-power (1063.00 ± 122.90 vs 1338.18 ± 127.40 W) variability. vV̇O2max was explained by power to overcome drag (r = .77, P ≤ .05) and η P (r = .72, P ≤ .05), in contrast with the nonassociation between these parameters and vAnT; both velocities were well related (r = .62, P ≤ .05).

Conclusions:

The biomechanical parameters, coordination, and metabolic power seemed not to be performance discriminative at either intensity. However, the increase in power to overcome drag, for the less metabolic input, should be the focus of any intervention that aims to improve performance at severe swimming intensity. This is also true for moderate intensities, as vAnT and vV˙O2max are proportional to each other.

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Helen C. Wright and David A. Sugden

The nature of developmental coordination disorder (DCD) in a selected group of Singaporean children (n = 69) aged 6-9 years was investigated by two methods: an intergroup comparison of children with DCD and matched controls (n = 69), and an intragroup study on the same children with DCD in the search for subtypes within this group. The results from the two approaches demonstrate that while the children with DCD are clearly different from the control subjects, the difficulties seen within the DCD group are not common to all the children. Four identifiable subtypes were found within the children with DCD. This more specific information gained about the difficulties children with DCD experience is not easily established from the intergroup analysis, suggesting that the design of future intervention studies should incorporate differences found in subtypes of children with DCD.

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

This study examined and compared the control of posture during bilateral stance in ten boys with Developmental Coordination Disorder (DCD) of 6-8 years old and ten matched typically developing boys in four sensory conditions (with or without vision, on a firm or complaint surface). In all conditions mean postural sway velocity was larger for the boys with DCD, in spite of a normal score on the balance items of the Movement Assessment Battery for Children. A Group X Condition interaction revealed a larger dependency on vision in the boys with DCD when standing on a firm surface. These results suggest that in this specific subgroup of boys with DCD with predominantly problems in fine motor and ball skills postural control problems may still be prevalent and may possibly be associated with difficulties to re-weight sensory information in response to environmental demands.

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Sarah J. Woodruff, Connie Bothwell-Myers, Maureen Tingley and Wayne J. Albert

The purpose was to develop an index of walking performance and to examine gait pattern classifications of children with developmental coordination disorder (DCD). The San Diego database (Sutherland, Olshen, Biden, & Wyatt, 1988) provided data for our calculation of the index and for determining that the index was able to differentiate between gait variables of older (ages 3 to 7) and younger (ages 1 to 2.5) children comprising the database. We obtained cinematographical data on 17 biomechanical markers of 6 boys and 1 girl, ages 6 to 7, with DCD, during walking. Analysis of individuals with DCD gait patterns revealed that most had abnormal walking patterns. The means of the time/distance gait variables did not differ between children with DCD and San Diego children, ages 3 to 7. Children with DCD had much larger variances than other children, indicating no systematic pattern in individual gait differences.

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Florian A. Kagerer, Jin Bo, Jose L. Contreras-Vidal and Jane E. Clark

Although one of the criteria for the diagnosis of developmental coordination disorder (DCD) suggests learning impairments, there is a lack of studies investigating motor adaptation in these children. This study examined the ability of 7 children with DCD to adapt to a novel visuomotor relationship by exposing them to a 45° visual feedback rotation while they performed a center-out drawing task, and compared their performance with that of 7 normally developing children. The results show that the children with DCD were less affected by the feedback distortion than the control children, and did not show aftereffects, suggesting they had a less well-defined internal model. A principal component analysis of the performance variables during early and late exposure showed that the variables accounting for most of the variance in the trajectories are different between the 2 groups, suggesting that underlying control processes might operate differently in the 2 groups of children.

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Michael A. Riley and David P. Black

Adaptation to prisms can produce a change in felt arm position, termed proprioceptive shift. We studied the effects of prism-induced proprioceptive shift on interlimb rhythmic coordination performed under proprioceptive guidance, in the absence of vision. Relative to interlimb rhythmic coordination performed before prism exposure, the observed steady states of relative phase for postexposure coordination were shifted by a small but reliable amount. The shift was in the direction expected, given the direction of optical displacement. The amount of variability of interlimb rhythmic coordination was unaffected by prism exposure. The results suggest that the same spatial frames of reference altered by prism adaptation are involved in the production of interlimb rhythmic coordination patterns.

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Tatiane Gorski, Thomas Rosser, Hans Hoppeler and Michael Vogt

Purpose:

To verify whether relative age effects (RAEs) occur among young male and female Swiss Alpine skiers of different age groups and performance levels. In addition, the efficacy of normalizing performance in physical tests to height and body mass to attenuate RAEs eventually present was tested.

Methods:

The Swiss Ski Power Test consists of anthropometric measures and physical tests for coordination and speed, endurance, and strength and has been used since 2004 to evaluate 11- to 19-y-old Swiss competitive Alpine skiers. The authors analyzed the distribution of 6996 tests performed by 1438 male and 1031 female Alpine skiers between 2004 and 2011 according to the athletes’ respective relative age quartiles. Differences in anthropometric measures and performance in physical tests according to quartile were assessed, and the possibility of attenuating eventual RAEs on performance by normalization of results to height and body mass was tested.

Results:

RAEs were found among all female and male age groups, with no differences between age groups. While performance level did not affect RAE for male skiers, it influenced RAE among female skiers. RAEs also influenced results in all physical tests except upper-limb strength. Normalization of results to body mass attenuated most RAEs identified.

Conclusion:

Small RAEs are present among young Swiss competitive Alpine skiers and should be taken into account in training and selection settings to prevent the waste of possible future talents. When ranking junior athletes according to their performance in physical tests, normalization of results to body mass decreases the bias caused by RAEs.