title: Examining impulse-variability in overarm throwing.
abstract: 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.
authors.affiliation: Auburn University-Department of Kinesiology, Auburn, AL, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Urbin
authors.forename: David
authors.initials: D
authors.lastname: Stodden
authors.forename: Rhonda
authors.initials: R
authors.lastname: Boros
authors.forename: David
authors.initials: D
authors.lastname: Shannon
mesh_terms: D001132:Arm / Q000502:physiology*; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D008297:Male; D009048:Motor Skills / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D055815:Young Adult