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This study was aimed at determining how the visual information of an end-effector (racket) and the intermediate extremity (arm) of a tennis server contribute to the receiver’s anticipatory judgement of ball direction. In all, 15 experienced tennis players and 15 novice counterparts viewed a spatially occluded computer graphics animation of a tennis serve (no-occlusion, racket-occlusion, and body-occlusion) and made anticipatory judgements of ball direction on a visual analogue scale (VAS). The patterns of the serve motions were generated by a simulation technique that computationally perturbs the rotation speed of the selected racket-arm joint (forearm pronation and elbow extension) on a captured serve motion. The results suggested that the anticipatory judgements were monotonically attuned with the perturbation rate of the forearm pronation speed excepting under the conditions of the racket-occlusion model. Although such attunements were not observed in the elbow perturbation conditions, the results of correlation analysis indicated that the residual information in the spatially occluded models had a similar effect to the no-occlusion model within the individual experienced participants. The findings support the notion that end-effector (racket) provides deterministic cues for anticipation, as well as imply that players are able to benefit from the relative motion of an intermediate extremity (elbow extension). more...

Many older adults perform collision-avoidance behavior either insufficiently (i.e., frequent collision) or inefficiently (i.e., exaggerated behavior to ensure collision-avoidance). The present study examined whether a training system using virtual reality (VR) simulation enhanced older adults’ collision-avoidance behavior in response to a VR image of an aperture during real walking. Twenty-five (n = 13 intervention group and n = 12 control group) older individuals participated. During training, a VR image of walking through an aperture was projected onto a large screen. Participants in the intervention group tried to avoid virtual collision with the minimum body rotation required to walk on the spot through a variety of narrow apertures. Participants in the control group remained without body rotation while walking on the spot through a wide aperture. A comparison between pre-test and post-test performances in the real environment indicated that after the training, significantly smaller body rotation angles were observed in the intervention group. This suggests that the training led participants to modify their behavior to try to move efficiently during real walking. However, although not significant, collision rates also tended to be greater, suggesting that, at least for some participants, the modification required to avoid collision was too difficult. Transfer of the learned behavior using the VR environment to real walking is discussed. more...

Objective Recent studies have reported that skilled tennis players are likely to use proximal body information for anticipating the direction of their opponent’s forehand shot. However, in these studies, the visual stimuli did not include visual information about the ball. Skilled players may have used proximal information owing to the lack of distal information. To address this issue, we developed a novel methodological approach using computer graphics (CG) images in which the entire body was presented by a combination of point-light display (i.e., poor graphical information, PLD) and polygons (i.e., rich graphical information). Using our novel methodological approach, we examined whether skilled tennis players use proximal body information when anticipating shot directions. Methods and results Fifteen skilled tennis players and fifteen novice players tried to anticipate shot directions by observing four CG forehand strokes (ALPOL: all body parts were represented with polygon; RAPLD: racket and arm were represented with PLD; BOPLD: body parts without racket and arm were represented with PLD; and ALPLD: all body parts were represented with PLD). Our intention in creating CG models with such combinations (i.e., RAPLD and BOPLD) was that because of the richer graphical information provided by polygons compared to PLD, the participant’s anticipatory judgment would be influenced more by body parts expressed with polygons. The results showed that for skilled players, anticipatory judgment was more accurate when they observed RAPLD than when they observed BOPLD and ALPLD. In contrast, for novice players, there were no differences in the accuracy of anticipatory judgments with the four CG models. Conclusions Only skilled players made more accurate anticipatory judgments when body regions were expressed with rich graphical information, and the racket and arm were expressed with poor graphical information. These suggest that skilled players used proximal information to effectively anticipate shot directions. more...

The purpose of this study was to determine whether and how the perceptual response of athletes differed depending on their sporting expertise. This was achieved by comparing the responses of tennis and soft tennis players. Twelve experienced tennis players and 12 experienced soft tennis players viewed computer graphic serve motions simulated by a motion perturbation technique, and then scaled their anticipatory judgments regarding the direction, speed, and spin of the ball on a visual analogue scale. Experiment 1 evaluated the player's judgments in response to test motions rendered with a complete polygon model. The results revealed significantly different anticipatory judgments between the player groups when an elbow rotation perturbation was applied to the test serve motion. Experiment 2 used spatially occluded models in order to investigate the effectiveness of local information in making anticipatory judgments. The results suggested that the isolation of visual information had less effect on the judgment of the tennis players than on that of the soft tennis players. In conclusion, the domain of sporting expertise, including those of closely related sports, cannot only differentiate the anticipatory judgment of a ball's future flight path, but also affect the utilization strategy for the local kinematic information. more...

The purpose of this study was to determine the quantitative relationships between the server's motion and the receiver's anticipation using a computer graphic animation of tennis serves. The test motions were determined by capturing the motion of a model player and estimating the computational perturbations caused by modulating the rotation of the player's elbow and forearm joints. Eight experienced and eight novice players rated their anticipation of the speed, direction, and spin of the ball on a visual analogue scale. The experienced players significantly altered some of their anticipatory judgment depending on the percentage of both the forearm and elbow modulations, while the novice players indicated no significant changes. Multiple regression analyses, including that of the racket's kinematic parameters immediately before racket – ball impact as independent variables, showed that the experienced players demonstrated a higher coefficient of determination than the novice players in their anticipatory judgment of the ball direction. The results have implications on the understanding of the functional relation between a player's motion and the opponent's anticipatory judgment during real play. more...

The Cave Automatic Virtual Environment (CAVE), which is a computer-simulated 3D virtual reality (VR) system, is expected to provide sport learners with interactive and immersive learning materials. The purpose of this study was to reveal perceptual characteristics of tennis players when they viewed the tennis ball flight reconstructed in CAVE. The visual stimuli of this study were reconstructed based on the actual measured values of the tennis court and the ball flight. Perceptual performances, subjective impression scoring and shot type discrimination (flat, topspin and slice), were assessed by varying the conditions of three visual VR settings: binocular disparity, screen number, and viewpoint. The augmented-disparity setting was likely to induce a higher sense of discomfort than the no-disparity and normal-disparity settings. The four-screen condition was more likely to induce a correct response than the one-screen condition. The viewpoint of the umpire induced a significantly higher sense of discomfort than the field player viewpoints, and the viewpoint close to the approaching ball made it more difficult to discriminate the shot type. This research was a pilot study on sport perception in VR, and the results will contribute to the construction of sport-simulating VR systems. more...

This study aimed to explore the feasibility of using computer graphics (CG) animations to evaluate perceptual skills in tennis. In Experiment 1, we used video images or CG animations to examine the visual search behaviors and the accuracy of anticipating serve direction of 18 skilled tennis players. Participants viewed the racket area for a longer time during the 150 ms period immediately before the moment of racket–ball contact in the video image condition opposed to the CG animation condition. In addition, the participants made more accurate judgments in the video image condition than in the CG animation condition. In Experiment 2, we investigated the information pick-up patterns of 10 skilled players while they viewed either the video images or CG animations using a temporal occlusion. Consistent with the results of Experiment 1, participants made more accurate judgments during the 150 ms period immediately before the contact in the video image condition than in the CG animation condition. The results of both experiments showed that the perceptual information in the 150 ms period differed between the two film types. However, the anticipation accuracy of the CG animation condition in both experiments was over the chance level (50%), suggesting that the participants were able to pick up the anticipatory information of serve direction from the CG animations. This led to the conclusion that CG animations would be a valuable tool to examine perceptual skills in tennis. more...

This study examined the perceptual effect of color and /or figuration information in human models created using computer graphics (CG) on anticipatory judgments of tennis serves. Fourteen skilled and fourteen novice tennis players attempted to anticipate serve direction by observing one live-action image and four CG animations (polygon, shadow, stick, and point-light) edited in accordance with a temporal occlusion paradigm. The dependent variable was the correct responses of serve directions (anticipation accuracy). The shadow, stick, and point-light models were simplified variations of the color and/or figuration information within a polygon model. At an occlusion of 30 ms before the moment of racket-ball impact, the skilled player's anticipation accuracy was superior to the chance level (50%) in the live-action and polygon model conditions, but not in the other three model conditions. In contrast with the results of skilled players, the novice player's anticipation accuracy did not exceed the chance level in all the conditions (model and occlusion). Moreover, the skilled players made more accurate judgments than their novice counterparts in the live-action and polygon model conditions. These results suggested that the skilled players used the color and figuration information in human models as visual information when they picked up the essential kinematic information from opponent's movement patterns. In addition, there were no significant differences in the skilled player's anticipation accuracy between the live-action and polygon model conditions. This led to the conclusion that our polygon model had sufficient quality to evaluate the superior anticipatory performance of skilled tennis players. more...

The present study was designed to investigate a relationship between the ability to quickly perform a mental rotation (MR) task using body (particularly foot) stimuli and postural stability during unipedal and bipedal quiet stance. Twenty-four healthy young adults participated in this study to measure reaction times for the MR (stimuli: foot, hand, and car), postural sway values during unipedal and bipedal standings, and lower extremity functions. Results showed significant correlations between the reaction time for the MR of the foot stimuli (but not for hand and car stimuli) and some of postural sway values (total length of sway and mean velocity in the anterior–posterior direction) during unipedal standing (but not for bipedal standing). Consistently, participants who performed the MR task quickly showed significantly smaller sway values during unipedal standing than those who performed the task slowly. These findings suggest that the ability to mentally imagine the foot movement is likely to relate to postural stability, while involving a challenging postural task, such as unipedal standing. The reaction time for the MR of foot stimuli was also correlated with two-point discrimination (TPD) distance on the plantar skin. Given that the TPD distance not only represents cutaneous acuity but also reflects participants’ body image relating to their feet, MR performance may have been related to postural stability because both involve cognitive processes used for both motor imagery and motor execution of the foot movement. more...

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. more...

Computer graphics of digital human models can be used to display human motions as visual stimuli. This study presents our technique for manipulating human motion with a forward kinematics calculation without violating anatomical constraints. A motion modulation of the upper extremity was conducted by proportionally modulating the anatomical joint angular velocity calculated by motion analysis. The effect of this manipulation was examined in a tennis situation--that is, the receiver's performance of predicting ball direction when viewing a digital model of the server's motion derived by modulating the angular velocities of the forearm or that of the elbow during the forward swing. The results showed that the faster the server's forearm pronated, the more the receiver's anticipation of the ball direction tended to the left side of the serve box. In contrast, the faster the server's elbow extended, the more the receiver's anticipation of the ball direction tended to the right. This suggests that tennis players are sensitive to the motion modulation of their opponent's racket-arm. more...