Author(s): OZAWA, Y., SHIMIZU, M., FURUYA, R., YAMADA, H., Institution: TOKAI UNIVERSITY, Country: JAPAN, Abstract-ID: 2219

INTRODUCTION:
Effective motor control relies on the integration of sensory information. In particular, sports movements are executed in real time and therefore depend critically on feedback from the sensory system for movement modulation. Motor programmes are assumed to incorporate optimal sensory feedback, enabling movement adjustments based on discrepancies between predicted and actual feedback. In the present study, we hypothesised that fine motor control requires accurate sensory feedback. To examine the relationship between movement accuracy and sensory feedback, predicted and actual landing positions were compared during a throwing task.
METHODS:
Five participants were instructed to throw a ball towards a target positioned at either 2 m (short) or 4 m (long) in front of them. Initially, participants completed 20 practice trials at each distance while visually observing the ball landing position. They subsequently performed 120 experimental trials under a blind condition in which the ball trajectory was occluded immediately after release. Ball landing positions were recorded using a high-speed camera (120 Hz; DSC-RX0M2, Sony, Japan). Immediately after each throw, participants marked their predicted landing position on a target image. Landing position data were analysed using Frame-DIAS VI (Q’s fix, Japan). The probabilistic structure of errors in both actual and predicted landing positions was evaluated using a 95% confidence ellipse, following previous studies. To characterise variability in predicted and actual landing positions, the major and minor axis lengths and the area of the 95% confidence ellipse were calculated. The relationships between these indices were examined using Pearson’s correlation coefficient.
RESULTS:
The area of the ellipse in the 2m trial was 0.11 ± 0.05 m^2, and that in the predicted landing point was 0.11± 0.07 m^2 (p = 0.325). And the area of the ellipse for the actual landing point in the 4m test was 0.40 ± 0.12 m^2, and that of the predicted landing point was 0.28 ± 0.12 m^2 (p = 0.044). No significant differences were found in the minor axis of the 95% confidence ellipse between indices in either the 2m or 4m trials (2 m: p = 0.118; 4 m: p = 0.398); however, the major axis was significantly shorter for the predicted than for the actual landing position (2 m: p = 0.005; 4 m: p = 0.007).
CONCLUSION:
Predicted landing area did not differ from the actual area in the 2m trials but was significantly smaller in the 4m trials. The major axis of the predicted landing ellipse was shorter than that of the actual ellipse and was aligned with the throwing direction. Because the ball trajectory was blinded after ball release, participants estimated projection velocity using tactile and proprioceptive cues at release, which, together with ball rotation, likely increased uncertainty in trajectory prediction. This mismatch between predicted and actual throwing directions may explain the observed reduction in the area of the 95% confidence ellipse.