Jackie L. Hudson

Coordination of segments in the vertical jump.

Three general patterns of segmental coordination (i.e., sequential [SEQ], simultaneous [SIM], and modified simultaneous [MSIM]) have been hypothesized for jumping. The purposes of this study were to describe the pattern of segmental coordination used in vertical jumping and to determine if skilled jumpers displayed distinguishing patterns of coordination. Maximum vertical jumps were performed in the counter movement (CMJ) and static jump (SJ) conditions by a heterogeneous group of 20 lean, adult subjects (AS). Smoothed, digitized film records provided the data for four segments: head-arms-trunk, trunk, thighs, and shanks. For each segment the phase of positive contribution was considered to begin with initiation of extension and end with maximum angular velocity. Bisegmental and multisegmental variables were defined to assess the extent of simultaneity. Skill was determined by the effective integration of the legs (ratio of peak upward velocity of CMJ and SJ) and by the use of stored elastic energy. Although 13 AS had MSIM patterns, the amount of flexion was small (less than or equal to 1 degree) so these AS were reclassified. With multisegmental analyses the number of AS with SIM patterns ranged from 13 to 17; about half the time was SIM. Using bisegmental analyses all 20 AS had SIM patterns; about three-fourths of the time was SIM. Skilled AS initiated extension and reached maximum velocity of the segments in proximal to distal order and with very small delays between adjacent segments.

Prediction of Basketball Skill Using Biomechanical Variables

Abstract This study was designed to examine the use of selected biomechanical variables in the prediction of basketball skill. The subjects were college women in three mutually exclusive groups of basketball skill: an elite group of six competitors on the United States team in the World University Games, a good group of seven players on a varsity team, and a poor group of nine members of an instructional class. An accuracy test and digitized film records provided the data for 12 variables related to the process or product of free throw shooting. Discriminant analysis was employed to predict the categorical variable of skill. The most discrimination came from variables of accuracy, stability, and height of release rather than from variables of projection. Poor shooters were distinguished by instability; elite shooters were characterized by a high point of release and accuracy under pressure. Depending on the method of prediction, rates for correct classification of subjects ranged from 76–100%. Thus, it ap...

Applied Biomechanics in an Instructional Setting

JOPERD • Volume 77 No. 8 • October 2006 H ow do biomechanists explain, analyze, and interpret movement in an instructional setting? When I am the biomechanist in question, I use a particular form of applied biomechanics. In my view, applied biomechanics is the science of how people move better. By better I mean more skillfully and more safely. In the material that follows, I will be placing more emphasis on skill rather than safety. However, there are many parallels between skillful and safe movement, and learning about skill can be a good way to learn about safety. Most biomechanists, it seems, prefer to take things apart, but I believe that applied biomechanics requires an integrated approach. Accordingly, I will share a few features of my paradigm of applied biomechanics before I discuss it in relation to a middle school football lesson.

Measurement of elastic-like behaviour in the power squat

Because traditional procedures of evaluating elastic-like behaviour have yielded mixed results, the purpose of this work was to explore two methods of measuring elastic-like behavior in the power squat. The entire concentric time method was based on traditional procedures. The initial concentric time method was developed to examine elastic-like behavior for the beginning 0.2 s of concentric movement. The present study compares a power squat performed maximally by nine subjects at 70% of their 1 repetition maximum. Squats were performed with rebound (REB) and without rebound (NRB). For the entire concentric time method only concentric time was significantly greater (p < 0.05) in the NRB than the REB. For the initial concentric time method the relative displacement, velocity, net work, & peak power of the center of mass were significantly greater (p < 0.05) in the REB than the NRB. Some subjects had theoretically infeasible negative results for elastic enhancement in the entire concentric time method, but not the initial concentric time method. It seems that measuring elastic-like behavior near the end of the movement can be confounded by the constraints of the task. Based on its success, the initial concentric time method appears to be more appropriate for measurement of elastic-like behavior in lifting.