The purpose of this study was to examine variability in overarm throwing velocity and spatial output error at various percentages of maximum to test the prediction of an inverted-U function as predicted by impulse-variability theory and a speed-accuracy trade-off as predicted by Fitts’ Law Thirty subjects (16 skilled, 14 unskilled) were instructed to throw a tennis ball at seven percentages of their maximum velocity (40–100%) in random order (9 trials per condition) at a target 30 feet away. Throwing velocity was measured with a radar gun and interpreted as an index of overall systemic power output. Within-subject throwing velocity variability was examined using within-subjects repeated-measures ANOVAs (7 repeated conditions) with built-in polynomial contrasts. Spatial error was analyzed using mixed model regression. Results indicated a quadratic fit with variability in throwing velocity increasing from 40% up to 60%, where it peaked, and then decreasing at each subsequent interval to maximum (p < .001, η2 = .555). There was no linear relationship between speed and accuracy. Overall, these data support the notion of an inverted-U function in overarm throwing velocity variability as both skilled and unskilled subjects approach maximum effort. However, these data do not support the notion of a speed-accuracy trade-off. The consistent demonstration of an inverted-U function associated with systemic power output variability indicates an enhanced capability to regulate aspects of force production and relative timing between segments as individuals approach maximum effort, even in a complex ballistic skill.
M.A. Urbin, David Stodden, Rhonda Boros, and David Shannon
Shannon Titus Dieringer, David L. Porretta, and Diane Sainato
The purpose of our study was to determine the effect of music (music with lyrics versus music with lyrics plus instruction) relative to on-task behaviors in preschool children with autism spectrum disorder (ASD) in a gross motor setting. Five preschool children (4 boys, 1 girl) diagnosed with ASD served as participants. A multiple baseline across participants in conjunction with an alternating-treatment design was used. For all participants, music with lyrics plus instruction increased on-task behaviors to a greater extent than did music with lyrics. The results of our study provide a better understanding of the role of music with regard to the behaviors of young children with ASD.