A scale-based approach to interdisciplinary research and expertise in sports.

After more than 20 years since the introduction of ecological and dynamical approaches in sports research, their promising opportunity for interdisciplinary research has not been fulfilled yet. The complexity of the research process and the theoretical and empirical difficulties associated with an integrated ecological-dynamical approach have been the major factors hindering the generalisation of interdisciplinary projects in sports sciences. To facilitate this generalisation, we integrate the major concepts from the ecological and dynamical approaches to study behaviour as a multi-scale process. Our integration gravitates around the distinction between functional (ecological) and execution (organic) scales, and their reciprocal intra- and inter-scale constraints. We propose an (epistemological) scale-based definition of constraints that accounts for the concept of synergies as emergent coordinative structures. To illustrate how we can operationalise the notion of multi-scale synergies we use an interdisciplinary model of locomotor pointing. To conclude, we show the value of this approach for interdisciplinary research in sport sciences, as we discuss two examples of task-specific dimensionality reduction techniques in the context of an ongoing project that aims to unveil the determinants of expertise in basketball free throw shooting. These techniques provide relevant empirical evidence to help bootstrap the challenging modelling efforts required in sport sciences.

The Influence of the 'Trier Social Stress Test' on Free Throw Performance in Basketball: An Interdisciplinary Study.

The aim of the present study was to explore the relationship between stress and sport performance in a controlled setting. The experimental protocol used to induce stress in a basketball free throw was the Trier Social Stress Test (TSST) and its control condition (Placebo-TSST). Participants (n = 19), novice basketball players but trained sportspersons, were exposed to two counterbalanced conditions in a crossover design. They were equipped with sensors to measure movement execution, while salivary cortisol and psychological state were also measured. The task consisted of two sequences of 40 free throws, one before either the TSST or Placebo-TSST and one after. Physiological and psychological measures evidenced that the TSST induced significant stress responses, whereas the Placebo-TSST did not. Shooting performance remained stable after the TSST but decreased after the Placebo-TSST. We found no effect of the TSST or Placebo-TSST on movement execution. A multivariate model of free throw performance demonstrated that timing, smoothness and explosiveness of the movements are more relevant to account for beginner's behavior than stress-related physiological and psychological states. We conclude that the TSST is a suitable protocol to induce stress responses in sport context, even though the effects on beginners' free throw performance and execution are small and complex.

The integration of temporally shifted visual feedback in a synchronization task: The role of perceptual stability in a visuo-proprioceptive conflict situation.

The present study examined whether the beneficial role of coherently grouped visual motion structures for performing complex (interlimb) coordination patterns can be generalized to synchronization behavior in a visuo-proprioceptive conflict situation. To achieve this goal, 17 participants had to synchronize a self-moved circle, representing the arm movement, with a visual target signal corresponding to five temporally shifted visual feedback conditions (0%, 25%, 50%, 75%, and 100% of the target cycle duration) in three synchronization modes (in-phase, anti-phase, and intermediate). The results showed that the perception of a newly generated perceptual Gestalt between the visual feedback of the arm and the target signal facilitated the synchronization performance in the preferred in-phase synchronization mode in contrast to the less stable anti-phase and intermediate mode. Our findings suggest that the complexity of the synchronization mode defines to what extent the visual and/or proprioceptive information source affects the synchronization performance in the present unimanual synchronization task.

Synchronising horizontal arm movement with transparent motion.

The relationship between perception and motor performance was studied in a situation that required perceptual processing of a complex motion stimulus in which a target signal had to be segmented, selected, and tracked. Participants were asked to move their arm in synchrony with one surface of a transparent motion display in which two surfaces moved horizontally back-and-forth over each other. The quality of tracking performance was measured as a function of bottom-up and top-down perceptual cues and their interplay. Target signal strength was manipulated by lowering the relative amount of signal dots constituting the target, i.e., the coherence level (100%-50%-30%-10%; the distractor surface was always 100% coherent). A colour cue that distinguished the target from the distractor surface was either available or absent. In the presence of a colour cue, participants experienced little or no difficulties at coherence levels of 50%-100% but when surface formation was complicated by lowering the coherence level, synchronisation consistency decreased. This corresponds with continuous attempts, successful and unsuccessful, to correct inaccurate synchronisation. In the absence of a colour cue, difficulties were frequently observed in all coherence conditions, but they differed depending on the coherence level. Overall, these results suggest that colour can serve as a strong top-down cue for proper target selection and tracking, provided that bottom-up motion signals are sufficiently strong.

The type of visual information mediates eye and hand movement bias when aiming to a Müller-Lyer illusion.

Aiming bias typically influences perception but action towards the illusory stimulus is often unaffected. Recent studies, however, have shown that the type of information available is a predictor for the expression of action bias. In the present cyclical aiming experiment, the type of information (retinal and extra-retinal) was manipulated in order to investigate the differential contributions of different cues on both eye and hand movements. The results showed that a Müller-Lyer illusion caused very similar perturbation effects on hand and eye-movement amplitudes and this bias was mediated by the type of information available on-line. Interestingly, the impact of the illusion on goal-directed movement was smaller, when information about the figure but not the hand was provided for on-line control. Saccadic information did not influence the size of the effect of a Müller-Lyer illusion on hand movements. Furthermore, the illusions did not alter the eye-hand coordination pattern. The timing of saccade termination was strongly linked to hand movement kinematics. The present results are not consistent with current dichotomous models of perception and action or movement planning and on-line control. Rather, they suggest that the type of information available for movement planning mediates the size of the illusory effects. Overall, it has been demonstrated that movement planning and control processes are versatile operations, which have the ability to adapt to the type of information available.

The effect of changed visual feedback on intention tremor in multiple sclerosis.

In patients with multiple sclerosis (MS), intention tremor amplitude is enhanced during the visually guided compared to the memory guided motor tasks. In the present study, the effect of visual feedback on intention tremor was investigated during visually guided wrist step-tracking tasks. Specifically, visual feedback of the hand was provided either instantly or averaged over different time windows. Thirteen MS patients with intention tremor and 14 healthy controls performed the wrist step-tracking task, while the visual representation of the actual hand position was displayed instantly or averaged over time windows of 150, 250 and 350 ms. It has been found in the patient group that, in association with a decreased initial error and decreased tremor amplitude on the screen, the amplitude of the actual performed tremor also decreased when visual feedback was changed. The tremor reduction was not different between conditions with manipulated feedback, although delays in presenting visual feedback of the hand position increased when the time window was larger. The reduction in overall tremor amplitude was unlikely related to other factors, such as eye fixation deficits or the speed of the primary hand movement. These results suggest that hand tremor severity is dependent on the visual feedback of position and movement errors.

Perceptual-motor adaptations in a synchronization task: the joint effects of frequency and motion coherence manipulations.

Two experiments were conducted to examine the human ability to adapt to a perturbation in a synchronization task. Five experimental signal conditions were tested using random-dot kinematograms, representing four conditions with different coherence levels (100%, 50%, 30% and 10%) and one target-alone condition. Within one trial, increasing or decreasing the frequency of the sinusoidally moving signal dots abruptly in the midst of each trial provoked a perturbation. The first experiment was aimed to clarify the process of adaptation to the new frequency situation. The second experiment explored the role of visual feedback about the arm's position on the participants' ability to adapt after the perturbation had occurred. The results clearly demonstrated that the synchronization performance gradually declined in function of the increasing number of randomly moving noise dots. In the 50% coherence condition, the participants were not or only partially able to adjust their arm movements to the new frequency situation. In addition, the provision of enhanced visual feedback about the arm's failed to improve one's adaptive ability. In general, these findings provided evidence for the important role of perceptual constraints on perception-action coupling in this type of synchronization task.

The influence of motion coherence manipulations on the synchronization level of a perception-action task.

The present experiment was conducted to examine the integration of the motion coherence paradigm in a synchronization task. Random-dot kinematograms were used to generate a pattern of oscillating dots representing four different coherence levels (10%, 30%, 50% and 100%) and one target-alone condition. The participants had to synchronize their arm with the coherently moving dots according to two different synchronization modes (in-phase and anti-phase). The results revealed a substantial performance decline when the target/noise ratio dropped under the critical threshold situated around the 30% coherence level, albeit independent of the synchronization mode. In general, these findings highlighted the impact of the perception of motion based on the level of motion coherence in the visual signal on the synchronization behavior in a perception-action setting.

Is the learning of goal-directed displacement effector-independent?

The present experiment was designed to investigate whether the learning of goal-directed locomotion is effector independent. To answer this question a bilateral transfer of learning paradigm was used. We wanted to find out whether learning can be transferred from a trained effector system to an untrained one. Sixteen participants were asked to proceed through virtual hallways, while walking on a treadmill or handling of a joystick, in order to cross a pair of oscillating doors. Participants received 1050 training trials on the specific effector system before being transferred to the untrained one. Results indicated a clear transfer from handling to walking and only a moderate transfer from walking to handling. This asymmetrical transfer provides partial support in favor of the effector independent hypothesis. Both the theoretical implications of this work and the possible mediating effect of calibration are discussed.

Exercise programs for older men: mode and intensity to induce the highest possible health-related benefits.

BACKGROUND: Although health-related benefits of fitness training in older men are well established, it is not clear yet which mode and intensity of a exercise program is most effective. This study addresses whether the combination of endurance (ED) and resistance training in older men have supplementary health-related benefits in addition to profits attained through endurance training alone. Additionally, effects of moderate- and low-intensity resistance training are compared. METHODS: Men, 55-75 years of age, were randomly assigned to a control group (N = 13) or one of three exercise groups (20 weeks, two to three times per week): endurance plus moderate resistance (MR) training (N = 22), endurance plus low resistance (LR) training (N = 22) and endurance training only (N = 22). Cardiovascular (CV) risk factors, muscular fitness and postural control were assessed before and after training. RESULTS: All exercise groups revealed significant (P < 0.05) improvements in resting heart rate, work capacity and recovery, waist girth, insulin response and knee-extensor strength with no differences among groups. Body composition, resting metabolic rate (RMR), VO2peak and postural control did not change in exercise groups. CONCLUSION: In older men, a fitness program consisting of 20 weeks endurance training combined with resistance training is equally effective as endurance training alone. Moderate vs. low resistance training added to endurance training yields similar health-related benefits.

The effects of enhanced visual feedback on human synchronization.

The execution of actions not only reposes on the spatial and temporal organization of the movements as such but also on their appropriate imbedding into the environmental spatio-temporal constraints. Actually, performance outcome appears to be strongly influenced by the strength of the perception-action coupling. The present experiment wants to examine to what degree this coupling strength affects the spatial and spatio-temporal characteristics of a synchronization task. In particular, the effects of: (i) enhanced visual feedback; and (ii) a modification in the spatial organization of the task were investigated. To do so, a task was designed in which horizontal arm movements had to be synchronized with a target light moving horizontally or vertically at a sinusoidal speed. Subjects performed six experimental conditions representing three synchronization modes (horizontal in-phase, horizontal anti-phase and orthogonal) and two feedback conditions (no feedback and feedback). The results for movement amplitude and relative phase revealed the operation of task specific effects. Apparently, the availability of feedback at the perception-action coupling level provoked the use of different strategies to cope with the constraints of this synchronization task.

The control of sequential aiming movements: the influence of practice and manual asymmetries on the one-target advantage.

The present experiment was conducted to explore the effect of practice on the one-target advantage in manual aiming, as well as asymmetries in intermanual transfer of training. Reaction and movement times for the first movement were longer in the 2-target than in the 1-target task, regardless of the amount of practice, hand preference and practice hand. When two movements were required, peak velocity was lower and, proportionally, more time was spent after peak velocity. Our kinematic results suggest that the one-target advantage is related to both predefined strategies as well as movement implementation processes during execution. Therefore, an integration of advance planning and on-line explanations for the one-target advantage is suggested. Regarding manual asymmetries, right-handers showed more transfer of training from the left to the right hand than vice versa. Left-handers exhibited a reversed pattern of asymmetric transfer of training to right-handers, but they were more disadvantaged using their non-dominant hand. These latter two findings have implications for models of manual asymmetry and upper limb control.

The learning of goal-directed locomotion: a perception-action perspective.

This study was designed to better understand the process underlying the learning of goal-directed locomotion. Subjects walked on a treadmill in a virtual reality setting and were asked to cross pairs of oscillating doors. The subjects behaviour was examined at the beginning of the learning process (pretest), after 350 trials (intermediate test), and after 700 trials (posttest). The data were analysed at three different levels, each representing a specific aspect of the global response: performance outcome, displacement kinematics, and current arrival condition. While some aspects of performance outcome suggested the presence of a ceiling effect in the intermediate test, both displacement kinematics and current arrival condition clearly highlighted continuous transformations of the control mechanism involved. The learning process is best described as (1) the establishing of a relationship between specific information and a movement parameter and (2) the optimization of this relationship. The optimization process is characterized by the further exploration of the available behavioural repertoire and by the refinement of the dialogue between information and movement.

When visuo-motor incongruence aids motor performance: the effect of perceiving motion structures during transformed visual feedback on bimanual coordination.

Two experiments are reported in which bimanual coordination tasks were performed under correct and transformed visual feedback conditions. Participants were to generate cyclical line-drawing patterns, with varying degrees of coordinative stability, while perceiving correct or transformed visual information of the trajectories on a screen. Visuo-motor transformations that dissociated the perceived movement direction from the actually generated direction, were applied to one or both limbs, resulting in varying degrees of perceptual grouping power. The transformed feedback did not influence the most stable coordination patterns (in-phase) whereas the accuracy and/or stability of the less stable coordination patterns (anti-phase and particularly orthogonal) benefited from particular visual feedback manipulations, i.e. when coherently grouped visual motion structures emerged, the quality of coordination improved significantly. These findings indicate that perceptual transformations aid the production of more complex coordination patterns, thereby underscoring the importance of perception-action coupling in bimanual coordination.

The effect of aging on the synchronization of human arm movements to external events.

The aim of this study was to analyze the synchronization of cyclical arm movements to an external event and to determine age-related differences when the coupling strength between perception and action is manipulated. A group of young and a group of older subjects had to track a moving light travelling horizontally while manipulating a lever in the same direction (in-phase) or in the opposite direction (anti-phase). The results showed a performance decrease for both age groups in the anti-phase condition as compared to the in-phase condition, yet this decrease was more pronounced for the older persons. Interestingly, this age effect disappeared with practice. Most likely the observed age-related performance decrement was due to the difficulties encountered by older people to correct on line movements when the visual information needed was not directly accessible. Nevertheless, this study also highlights the capacity of older people to regain the performance loss through training.

Control of human locomotion under various task constraints.

The goal of this study was to identify the control mechanism used for locomotion pointing regulation under different external temporal constraints. Subjects ( n=8) had to walk on a treadmill through a number of virtual hallways and cross a pair of gliding doors that opened and closed at a constant preset frequency (0.5 Hz or 1 Hz). Crossing performance, step durations, and step lengths were used as dependent measures. The results revealed the regulation of locomotion occurred earlier and was more pronounced at 0.5 Hz than at 1 Hz, making performance better at 0.5 Hz. Nevertheless at the two frequencies the control mechanism appears similar; it is grounded on information movement coupling. This control mechanism allows for the production of specific behavior according to the task constraints.