Fastball pitches of eight collegiate baseball pitchers were filmed using the Direct Linear Transformation (DLT) method of three-dimensional (3D) cinematography. Coordinate data were obtained, and the model developed by Feltner and Dapena (1989) was used to fractionate the 3D angular acceleration of the upper arm and distal segment (the forearm, the hand, and prior to release, the baseball) of the throwing arm into terms associated with the joint torques exerted on the segments and the kinematic variables used to define the motions of the segments. The findings indicated that the extreme external rotation of the upper arm during the pitch was due mainly to the sequential actions of the horizontal adduction and abduction muscles at the shoulder. The study also found that the rapid elbow extension prior to ball release was due primarily to the counterclockwise angular velocity of the upper arm and trunk (viewed from above) that occurred during the pitch, and not to the elbow extensor muscles.
Michael E. Feltner and Jesús Dapena
The motion of a body segment is determined by joint torques and by the motions of the segments proximal or distal to it. This paper describes a three-dimensional model that was used to determine the effects of the shoulder and elbow joint torques and of the upper trunk and arm motions on the angular accelerations of the arm segments during baseball pitching. Equations were developed to fractionate the three-dimensional components of the angular acceleration vector of each segment into angular acceleration terms associated with the joint torques made on the segment, and into various “motion-dependent” angular acceleration terms associated with the kinematic variables of the arm segments. Analysis of the values of the various motion-dependent angular acceleration terms permitted the determination of their contributions to the motion of the segment. Although the model was developed to provide further understanding of the mechanics of the throwing arm during baseball pitching, it can be used to analyze any two-segment two-dimensional or three-dimensional motion.
Jesús Dapena and Michael E. Feltner
A method for adjusting the effects of wind and altitude on the times of 100-meter sprint races was developed in three stages: (a) generation of an initial model, (b) evaluation of the initial model using a test based on statistical information from world-class sprinting races, and (c) modification of the model to make its predictions fit with the statistical data. The test used to check the accuracy of the model's predictions involved a compilation of the 100 best races ever run (after adjustment of the times for wind and altitude effects), and a comparison of the average wind reading of these races with the average wind reading of all races. The modified form of the model predicted a 0.07-second advantage for a 2-m/s tail wind, a 0.085-s disadvantage for a 2-m/s head wind, and a 0.05-s advantage for the altitude of Mexico City (2,250 m). These values were clearly smaller than those predicted by previous models. If the modified model is correct, this implies that times made with aiding wind and/or at high altitude have greater merit than was previously thought.
Michael E. Feltner and Grant Taylor
The purpose of the study was to examine the resultant joint forces (RJFs) and torques (RJTs) at the shoulder, elbow, and wrist during penalty throws and determine the relationships between muscle actions and motions of the throwing arm. Subjects with an overhand (OH) throwing technique created larger maximal and average RJTs at the shoulder and elbow compared to subjects with a sweep (SW) technique (Feltner & Nelson, 1996). Prior to release, OH technique subjects decreased their abduction torque and created adduction torques at the shoulder. Adduction torques and downward vertical motion of the trunk, together with an internal rotation torque at the shoulder, resulted in large internal rotation angular velocities at release for the OH technique subjects. The SW technique subjects did not exhibit these technique characteristics. Additionally, throwing technique exhibited a moderate but positive relationship with several chest, upper arm, and forearm circumference measures. Findings suggest that muscular strength may be a causal determinant of technique style.
Michael E. Feltner and September T. Nelson
The purpose was to compute the instantaneous contributions of anatomical rotations of the trunk, upper arm, forearm, and hand to ball speed and to quantify the three-dimensional angular kinematics of the trunk and throwing arm during water polo penalty throws. The largest contributors to predicted ball speed |(vB)'| at release were forearm extension and a counterclockwise twisting rotation of the trunk. Upper arm internal rotation contribution to |(vB)'| at release was highly variable and exhibited a significant inverse relationship with the upper arm horizontal adduction contribution to |(vB)'| at release (r = −.70). Subjects with large internal rotation contributions to |(vB)'| tended to have the upper arm in positions of less external rotation, but internally rotating at a faster rate, at release. Subjects with large upper arm horizontal adduction contributions to |(vB)'| exhibited a trend for faster rates of upper arm horizontal adduction and positions of increased forearm pronation at release. Findings suggest that a continuum of technique styles are used by water polo players to produce ball speed at release.
Priscilla Gilliam MacRae, Michael E. Feltner and Sibylle Reinsch
This study examined the effects of a 1-year low intensity exercise program in community dwelling older women on falls, injuries, and risk factors for falls such as poor balance, muscular weakness, and gait abnormalities. Eighty older women were assigned to an exercise (Ex, n = 42) or attention control (Co, n = 38) group. During the 1-year study, 36% of the Ex group experienced a fall compared to 45% of the Co group (χ2 = 0.22, p ≥ 0.05). None of the 10 fallers in the Ex group suffered an injury that required medical attention, compared with 3 of the 14 fallers (21%) in the Co group. Further analyses indicated that the Co group declined significantly in isometric strength of the knee extensors and ankle dorsiflexors while the Ex group did not change significantly across the 1-year study. On measures of hip abductor strength, balance, and gait, the groups were not significantly different from each other pre- to post intervention.
Steven A. Kautz, Michael E. Feltner, Edward F. Coyle and Ann M. Baylor
A pedal dynamometer recorded changes in pedaling technique (normal and tangential components of the applied force, crank orientation, and pedal orientation) of 14 elite male 40-km time trialists who rode at constant cadence as the workload increased from similar to an easy training ride to similar to a 40-km competition. There were two techniques for adapting to increased workload. Seven subjects showed no changes in pedal orientation, and predominantly increased the vertical component of the applied force during the downstroke as the workload increased. In addition to increasing the vertical component during the downstroke, the other subjects also increased the toe up rotation of the pedal throughout the downstroke and increased the horizontal component between 0° and 90°. A second finding was that negative torque about the bottom bracket during the upstroke usually became positive (propulsive) torque at the high workload. However, while torque during the upstroke did reduce the total positive work required during the downstroke, it did not contribute significantly to the external work done because 98.6% and 96.3 % of the total work done at the low and high workloads, respectively, was done during the downstroke.