Search Results

This study examined variability in throwing speed and spatial error to test the prediction of an inverted-U function (i.e., impulse-variability [IV] theory) and the speed-accuracy trade-off. Forty-five 9- to 11-year-old children were instructed to throw at a specified percentage of maximum speed (45%, 65%, 85%, and 100%) and hit the wall target. Results indicated no statistically significant differences in variable error across the target conditions (p = .72), failing to support the inverted-U hypothesis. Spatial accuracy results indicated no statistically significant differences with mean radial error (p = .18), centroid radial error (p = .13), and bivariate variable error (p = .08) also failing to support the speed-accuracy trade-off in overarm throwing. As neither throwing performance variability nor accuracy changed across percentages of maximum speed in this sample of children as well as in a previous adult sample, current policy and practices of practitioners may need to be reevaluated.

Individual body segment actions evolve during throwing skill development. Maximal trunk involvement is typically the last feature of the movement pattern to fully develop. The current study examined developmental levels of trunk action and the associated variability in the throwing motion. The throwing motions of children and adolescents were analyzed via motion capture and trunk actions were classified as exhibiting no rotation (n = 7), blocked rotation (n = 6), or differentiated rotation (n = 11). Results indicated nonrotators exhibited greater variability than blocked-rotators in maximum humeral external rotation and humeral horizontal adduction angles at ball release; nonrotators also demonstrated greater variability than differentiated-rotators on these parameters, in addition to forward trunk tilt and elbow extension angle at ball release. Nonrotators produced more variable peak upper torso and humeral horizontal adduction angular velocities, as well as peak upper torso linear velocity, relative to differentiated-rotators. Blocked-rotators produced more variable peak pelvis, upper torso, and humeral horizontal adduction angular velocities, as well peak pelvis linear velocity, relative to differentiated-rotators. Nonrotators were less consistent relative to blocked- and differentiated-rotators in the time that elapsed from peak pelvis angular velocity to ball release. These results indicate that greater trunk involvement is associated with more consistent movement production.

Motor competence is associated with psychological and physical health outcomes. A reciprocal relationship between motor competence and perceptions of physical competence exists, but the developmental trajectory of the motor competence/perceived competence relationship is not well understood. Standardized assessments take a product- or process-oriented approach, but research concerning the motor competence/perceived competence relationship is limited to using process-oriented assessments. It is unknown whether boys and girls use product and process information differentially in the development of perceived competence. Children (N = 411) were aggregated into age groups. Perceived competence and product and process aspects of motor competence were assessed. Older children were more skillful than younger children but reported lower perceived competence. The motor competence/perceived competence association increased for both motor competence measures across age groups. Girls demonstrated stronger associations between process measures of motor competence and perceived competence, while boys indicated stronger associations between product measures of motor competence and perceived competence. When both motor competence measures were used to predict perceived competence, more variance in perceived competence was explained, compared with using independent predictors. The strength of the prediction increased across age groups, indicating that motor competence is a stronger predictor of perceived competence in older children.

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.

This study examined variability in kicking speed and spatial accuracy to test the impulse-variability theory prediction of an inverted-U function and the speed-accuracy trade-off. Twenty-eight 18- to 25-year-old adults kicked a playground ball at various percentages (50–100%) of their maximum speed at a wall target. Speed variability and spatial error were analyzed using repeated-measures ANOVA with built-in polynomial contrasts. Results indicated a significant inverse linear trajectory for speed variability (p < .001, η²= .345) where 50% and 60% maximum speed had significantly higher variability than the 100% condition. A significant quadratic fit was found for spatial error scores of mean radial error (p < .0001, η² = .474) and subject-centroid radial error (p < .0001, η² = .453). Findings suggest variability and accuracy of multijoint, ballistic skill performance may not follow the general principles of impulse-variability theory or the speed-accuracy trade-off.

Background: The objective was to examine changes of children’s time spent in sedentary, light physical activity, moderate to vigorous physical activity (MVPA), and estimated energy expenditure (EE) rates during weekdays and weekends across 3 years. Methods: An initial sample of 261 children’s (mean age = 7.81 y) 5-day physical activity and EE were assessed annually via accelerometry across 3 years using repeated-measures multivariate analysis of variance. The outcome variables were time spent in sedentary, light physical activity, MVPA, and kilocalories per day for weekdays and weekends. Results: A significant decrease in MVPA and EE occurred during weekdays across the 3 years (P = .01). Only the second-year data demonstrated an increase (+2.49 min) in weekend MVPA (P = .04). Children’s sedentary time during weekdays increased significantly in years 1 and 2 (P = .01), yet significantly decreased in the third year (−44.31 min). Children’s sedentary time during weekends significantly decreased in the first year (−27.31 min), but increased in the following 2 years (P = .01). Children’s light physical activity demonstrated a statistically significant increase in year 2 (+3.75 min) during weekdays (P = .05). Conclusions: Children’s MVPA and EE generally declined during weekdays but were maintained during weekends across a 3-year time span. Children may benefit most from weekday intervention strategies.

This paper examined relationships between qualitative (developmental sequences) and quantitative (time) performance in rising from a supine position in early childhood. One hundred twenty two children ranging in age from 3 to 5 years were videotaped for five trials of rising from a supine position. Children’s performance on the supine-to-stand (STS) task was quite variable in terms of both qualitative movement patterns and time (mean = 2.37 s, SD = .60). Results: Component sequences were moderately to strongly correlated with each other (r = .387 to .791). Upper-extremity (r = –.383) and axial (r = –.416) component levels also were inversely correlated with STS time. Results indicated a strong coordinative link between the development of trunk control (i.e., axial movement) and upper-extremity movement levels (r = .791), and together they demonstrated the strongest impact on the ability to rise quickly. These data provide important information relating to a child’s motor development that may have clinical relevance for diagnosis. It provides also a greater understanding on how to improve performance on this task. Future research should examine qualitative and quantitative aspects of STS performance to understand its predictive utility as a lifespan assessment of motor competence and its potential importance as a measure to predict healthrelated variables and functional capability across the lifespan.