A Biomechanical Comparison Of Developmental Stages Of The Standing Long Jump

Abstract

The purpose of this study was to investigate a developmental staging sequence of the standing long jump. Specifically, the biomechanical factors associated with the performance of this skill were compared in order to determine which variables differentiated between the individual stages. Kinematic, kinetic, and anthropometric data on thirty-three subjects (25 males and 8 females) between the ages of 4 and 7 years were collected. Kinematic data were collected using a 16mm LOCAM high-speed camera equipped with a F 12-1200mm zoom lens. Kinetic data were collected using an AMTI force platform and specially written software. The kinematic data were digitized from film projected onto a drafting table by a Van Guard Motion Analyzer. Data were reduced and analyzed by specially written computer software including a double-pass Butterworth filter for data smoothing. Statistical treatment of the data included a multivariate analysis of variance (MANOVA) on each set of variables to control for the overall alpha level. Significant MANOVAS were followed up by univariate ONE-WAY analysis of variance tests. Within cell sample sizes (stages 1-4) were 5, 12, 11, and 5 for all variables included in the analysis. The results of the analysis revealed that no descriptive variable (age, weight, and percent body fat) or segmental mass accounted for significant variance between stages. The horizontal distance jumped (F[3, 29] =5.03, ) and horizontal distance between the heels and center of mass of the subject at the moment of landing (F[3,29] =6.65, ) were both significant. Acceleration of body segments showed several variables differentiated between stages. The acceleration of the thighs (F[3, 29] =3.91, ), acceleration of the trunk (F[3, 29] =3.10, ), acceleration of the arms . (F[3, 29] =5.00, ), and acceleration of the forearms (F[3, 29] =13.51, ) were all significant at the .05 level. The resultant segmental force contribution of the forearms (F[3, 29] =4.99, ) was significant. Force platform data showed that the peak propulsive force (F[3, 29] =15.67, ), resultant magnitude of force (F[3, 29] =3.56, ), and the angle of force production (F[3, 29] =3.55, ) were all significant. The results of this study indicate that the observable visual cues used to determine the developmental stages of motor performance of the standing long jump may be reduced. A recommendation was made that the contributions of the arms at the moment of takeoff and position of the thighs relative to horizontal at the moment of landing are valuable visual cues. The implications of these results for teachers of fundamental motor skills were discussed.