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  • Author: Luc Tremblay x
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Marlene Luis and Luc Tremblay

We aimed to determine if visual feedback use during aerial skills is more efficient at low angular head velocity (AHV; i.e., <350 deg/s) than at high AHV. Twelve experienced female acrobats performed 20 back tuck somersaults under four experimental conditions: full-vision (FV), vision at AHV below 350 deg/s (VBelow), vision at AHV above 350 deg/s (VAbove), and no-vision (NV). AHV was calculated in real time, and liquid crystal goggles were used to manipulate vision. Two gymnastics judges scored landing stability using a four-point scale. All vision conditions that allowed some vision yielded significantly better landing scores than in the NV condition. Furthermore, a nonparametric test revealed that VBelow yielded a better performance ranking than the FV condition. We conclude that visual feedback during a back tuck somersault is used for landing stability at all angular head velocities, but optimal feedback use occurs when there is retinal stability.

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John de Grosbois and Luc Tremblay

A major challenge to the measurement of online control is the contamination by offline, planning-based processes. The current study examined the sensitivity of four measures of online control to offline changes in reaching performance induced by prism adaptation and terminal feedback. These measures included the squared Z scores (Z 2) of correlations of limb position at 75% movement time versus movement end, variable error, time after peak velocity, and a frequency-domain analysis (pPower). The results indicated that variable error and time after peak velocity were sensitive to the prism adaptation. Furthermore, only the Z 2 values were biased by the terminal feedback. Ultimately, the current study has demonstrated the sensitivity of limb kinematic measures to offline control processes and that pPower analyses may yield the most suitable measure of online control.

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Marlowe Pecora, Luc Tremblay and Matthew Heath

Reaches with overlapping stimulus-response spatial relations (propointing) adhere to speed–accuracy relations as defined by Paul Fitts’ index of difficulty equation (IDFitts: in bits of information). This movement principle is attributed to response mediation via the “fast” visuomotor networks of the dorsal visual pathway. It is, however, unclear whether the executive demands of dissociating stimulus-response spatial relations by reaching mirror-symmetrical to a target (antipointing) elicits similar adherence to Fitts’ equation. Here, pro- and antipointing responses were directed to a constant target amplitude with varying target widths to provide IDFitts values of 3.0, 3.5, 4.3, and 6.3 bits. Propointing movement times linearly increased with IDFitts—a result attributed to visually based trajectory corrections. In contrast, antipointing movement times, deceleration times, and endpoint precision did not adhere to Fitts’ equation. These results indicate that antipointing renders a “slow” and offline mode of control mediated by the visuoperceptual networks of the ventral visual pathway.

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Luc Tremblay, Timothy N. Welsh and Digby Elliott

Although proponents of the motor schema theory hold that a decrease in the reliance on afferent information will occur with practice in consort with the development of motor programs, supporters of the specificity of practice hypothesis suggest that a performer's reliance on the available sources of afferent information during acquisition increases with the amount of practice. To reconcile these competing positions, four groups of 9 participants aimed to targets under either a constant or a variable practice schedule, with or without vision of the effector. After modest (15 trials) and moderate (150 trials) practice, participants were tested in both their own and in the alternate vision condition. Results indicate mat the utilization of online kinesthetic information was enhanced through practice regardless of the availability of vision during acquisition. This was especially true for the groups practicing under a variable practice schedule.

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Cheryl Glazebrook, Digby Elliott, James Lyons and Luc Tremblay

This study investigated inhibition of return in persons with and without Down syndrome (DS) when visual or verbal cues were used to specify a target in a crossmodal paradigm. Individuals with DS and without DS performed manual aiming movements to a target located in right or left hemispace. The target was specified by an endogenous visual or verbal stimulus. Both groups were significantly slower when responding to the same target as the previous trial when the target was cued in a different modality. Although participants with DS initiated and executed their movements more slowly, they demonstrated a similar pattern of inhibition as people without DS, suggesting that inhibitory processes are functioning normally in persons with DS.

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Maxime Trempe, Jean-Luc Gohier, Mathieu Charbonneau and Jonathan Tremblay

In recent years, it has been shown that spacing training sessions by several hours allows the consolidation of motor skills in the brain, a process leading to the stabilization of the skills and, sometimes, further improvement without additional practice. At the moment, it is unknown whether consolidation can lead to an improvement in performance when the learner performs complex full-body movements. To explore this question, we recruited 10 divers and had them practice a challenging diving maneuver. Divers first performed an initial training session, consisting of 12 dives during which visual feedback was provided immediately after each dive through video replay. Two retention tests without feedback were performed 30 min and 24 hr after the initial training session. All dives were recorded using a video camera and the participants’ performance was assessed by measuring the verticality of the body segments at water entry. Significant performance gains were observed in the 24-hr retention test (p < .05). These results suggest that the learning of complex full-body movements can benefit from consolidation and that splitting practice sessions can be used as a training tool to facilitate skill acquisition.

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Darian T. Cheng, Gerome A. Manson, Andrew Kennedy and Luc Tremblay

Cheng et al. (2008) showed that when goal-directed reaching movements are performed with a 2.5 s inter-trial interval (ITI) under a randomized visual feedback schedule, individuals use online visual information on trial n to perform efficient online corrections on trial n + 1 (i.e., “reminiscence” effect). These results persisted even when participants were given knowledge of the up-coming vision condition. In this study, the ITI was extended to 5 s in an attempt to negate any effects of the preceding trial. Results from this study revealed that trials with vision were always more accurate than trials performed without vision, suggesting that individuals relied significantly on online information. Furthermore, aiming precision improved when participants knew the vision condition before each trial. It is thus suggested that the reminiscence effects are not longer evident with a 5 s ITI, which in turn allows prior knowledge of visual feedback to influence the use of online vision.

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Stephen R. Bested, Gerome A. Manson and Luc Tremblay

Robotic guidance has been employed with limited effectiveness in neurologically intact and patient populations. For example, our lab has effectively used robotic guidance to acutely improve movement smoothness of a discrete trajectory without influencing movement endpoint distributions. The purpose of the current study was to investigate the efficacy of combining robotic guidance and unassisted trials in the learning of a golf putting task. Participants completed a pre-test, an acquisition phase, and an immediate and delayed (24-hour) post-test. During the pre-test, kinematic data from the putter was converted into highly accurate, consistent, and smooth trajectories delivered by a robot arm. During acquisition, three groups performed putts towards three different targets with robotic guidance on either 0%, 50%, or 100% of acquisition trials. Only the 50% guidance group statistically reduced both the ball endpoint distance and variability between the pre-test and the immediate or 24-hr post-test. The results of the 50% guidance group yielded seminal evidence that combining both unassisted and robotic guidance trials (i.e., mixed practice) could facilitate at least short-term motor learning for a golf putting task. Such work is relevant to incorporating robotic guidance in sport skills and other practical areas (e.g., rehabilitation).

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Grant R. Tomkinson, Justin J. Lang, Joel Blanchard, Luc A. Léger and Mark S. Tremblay

Cardiorespiratory fitness (CRF) is a good summative measure of the body’s ability to perform continuous, rhythmic, dynamic, large-muscle group physical activity, and exercise. In children, CRF is meaningfully associated with health, independent of physical activity levels, and it is an important determinant of sports and athletic performance. Although gas-analyzed peak oxygen uptake is the criterion physiological measure of children’s CRF, it is not practical for population-based testing. Field testing offers a simple, cheap, practical alternative to gas analysis. The 20-m shuttle run test (20mSRT)—a progressive aerobic exercise test involving continuous running between 2 lines 20 m apart in time to audio signals—is probably the most widely used field test of CRF. This review aims to clarify the international utility of the 20mSRT by synthesizing the evidence describing measurement variability, validity, reliability, feasibility, and the interpretation of results, as well as to provide future directions for international surveillance. The authors show that the 20mSRT is an acceptable, feasible, and scalable measure of CRF and functional/exercise capacity, and that it has moderate criterion validity and high to very high reliability. The assessment is pragmatic, easily interpreted, and results are transferable to meaningful and understandable situations. The authors recommend that CRF, assessed by the 20mSRT, be considered as an international population health surveillance measure to provide additional insight into pediatric population health.