COMPUTER-BASED LEARNING USING CAPTURED TENNIS SERVE MOTION

INTRODUCTION: Motion analysis techniques have revealed kinetic and kinematic aspects of the sport motions, however, more intuitive resources, e.g. visual feedback, would be recommended to the sport practitioners. Féry & Crognier (2001) showed that essential anticipatory information is contained in the opponent’s stroke motion whatever the tactical significance of the situation. Fukuhara et al (2005) proposed that computer graphics animation have possibilities to be utilized in the sport visual training. This study aimed to explore the effect of computer-based visual learning in tennis by testing the judgment performance of novice player who viewed a captured tennis serve animation

Can Slow-Motion Footage of Forehand Strokes Be Used to Immediately Improve Anticipatory Judgments in Tennis?

Slow-motion footage of sports actions is widely used as a visual learning tool in observing the dynamic motor behaviors of athletes. Recent studies on action observation have reported that extending the observation time in slow-motion footage provides benefits of understanding the intention of an opponent’s action, at least when observing rapid movements. As such, the use of slow-motion footage may have the potential to improve the anticipatory judgments of an opponent’s action outcome without training (or feedback). To verify this possibility, we examined the effects of the replay speed of slow-motion footage on the anticipatory judgments of shot directions and recognition of kinematic positions of opponents’ forehand strokes in tennis. Nine skilled and nine novice tennis players were asked to anticipate the direction of their opponent’s shots (left or right) and then attempted to recognize proximal (trunk center) and distal (ball) kinematic positions. Computer graphic animations of forehand strokes were used as visual stimuli, which were presented at four different replay speeds (normal, three-quarter, half, and quarter speeds). We failed to show the immediate effect of the use of slow-motion footage on the anticipatory performance of the skilled and novice players, although the anticipatory performance of the skilled players was superior to that of the novice players. Instead, we found an effect of the use of slow-motion footage in terms of promoting recognition of important kinematic cues (trunk center) for effective anticipation by skilled players. Moreover, no significant correlations were observed between the anticipatory judgments and motion recognition in all experimental conditions. These results suggest that even if the use of slow-motion footage enhances the recognition of key kinematic cues, it may not immediately improve anticipatory judgments in tennis

Voluntary self-touch increases body ownership

Experimental manipulations of body ownership have indicated that multisensory integration is central to forming bodily self representation. Voluntary self touch is a unique multisensory situation involving corresponding motor, tactile and proprioceptive signals. Yet, even though self-touch is frequent in everyday life, its contribution to the formation of body ownership is not well understood. Here we investigated the role of voluntary self touch in body ownership using a novel adaptation of the rubber hand illusion (RHI), in which a robotic system and virtual reality allowed participants self-touch of real and virtual hands. In the first experiment, active and passive self-touch were applied in the absence of visual feedback. In the second experiment, we tested the role of visual feedback in this bodily illusion. Finally, in the third experiment, we compared active and passive self-touch to the classical RHI in which the touch is administered by the experimenter. We hypothesized that active self-touch would increase ownership over the virtual hand through the addition of motor signals strengthening the bodily illusion. The results indicated that active self-touch elicited stronger illusory ownership compared to passive self-touch and sensory only stimulation, and show an important role for active self-touch in the formation of bodily self

Recognition of Tennis Serve Performed by a Digital Player: Comparison among Polygon, Shadow, and Stick-Figure Models

<div><p>The objective of this study was to assess the cognitive effect of human character models on the observer's ability to extract relevant information from computer graphics animation of tennis serve motions. Three digital human models (polygon, shadow, and stick-figure) were used to display the computationally simulated serve motions, which were perturbed at the racket-arm by modulating the speed (slower or faster) of one of the joint rotations (wrist, elbow, or shoulder). Twenty-one experienced tennis players and 21 novices made discrimination responses about the modulated joint and also specified the perceived swing speeds on a visual analogue scale. The result showed that the discrimination accuracies of the experienced players were both above and below chance level depending on the modulated joint whereas those of the novices mostly remained at chance or guessing levels. As far as the experienced players were concerned, the polygon model decreased the discrimination accuracy as compared with the stick-figure model. This suggests that the complicated pictorial information may have a distracting effect on the recognition of the observed action. On the other hand, the perceived swing speed of the perturbed motion relative to the control was lower for the stick-figure model than for the polygon model regardless of the skill level. This result suggests that the simplified visual information can bias the perception of the motion speed toward slower. It was also shown that the increasing the joint rotation speed increased the perceived swing speed, although the resulting racket velocity had little correlation with this speed sensation. Collectively, observer's recognition of the motion pattern and perception of the motion speed can be affected by the pictorial information of the human model as well as by the perturbation processing applied to the observed motion.</p> </div

Discrimination accuracy of modulated joint.

<p>Percentage of correct responses (<i>M</i> ± <i>SD</i>) for the experienced group (A) and novice group (B). *: <i>p</i><.05 in planned two-way ANOVA, †: above chance level (33.3%), and ‡: below chance level.</p

VAS score (<i>M</i> ± <i>SD</i>) of perceived swing speed.

<p>Minimum score = 0 (slow), maximum score = 100 (fast) and control motion = 50.</p>*<p>: significant main effect (p<.05).</p

Optimal integration of kinematic and ball-flight information when perceiving the speed of a moving ball

In order to intercept a moving target such as a baseball with high spatio-temporal accuracy, the perception of the target's movement speed is important for estimating when and where the target will arrive. However, it is unclear what sources of information are used by a batter to estimate ball speed and how those sources of information are integrated to facilitate successful interception. In this study, we examined the degree to which kinematic and ball-flight information are integrated when estimating ball speed in baseball batting. Thirteen university level baseball batters performed a ball-speed evaluation task in a virtual environment where they were required to determine which of two comparison baseball pitches (i.e., a reference and comparison stimuli) they perceived to be faster. The reference and comparison stimuli had the same physical ball speed, but with different pitching movement speeds in the comparison stimuli. The task was performed under slow (125 km/h) and fast (145 km/h) ball-speed conditions. Results revealed that the perceived ball-speed was influenced by the movement speed of the pitcher's motion, with the influence of the pitcher's motion more pronounced in the fast ball-speed condition when ball-flight information was presumably less reliable. Moreover, exploratory analyses suggested that the more skilled batters were increasingly likely to integrate the two sources of information according to their relative reliability when making judgements of ball speed. The results provide important insights into how skilled performers may make judgements of speed and time to contact, and further enhance our understanding of how the ability to make those judgements might improve when developing expertise in hitting