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Contributions of Angular Momentum and Catting to the Twist Rotation in High Jumping

Jesús Dapena

This project sought to break down high jump twist rotation into portions contributed by angular momentum and those contributed by rotational action and reaction ("catting"). Five male and 5 female high jumpers were studied with three-dimensional film/video analysis procedures. The hip twist angle at the peak was broken down into an initial twist angle at takeoff and the subsequent twist rotation accumulated between takeoff and the peak. The latter was in turn broken down into rotations contributed by the twisting component of angular momentum and rotations contributed by catting. It was found that the contribution of catting to the twist rotation was at least as large as that of the angular momentum. The important contribution of catting to the twist rotation introduces the possibility that defects in its execution might play a role in the problems that some high jumpers have with twist rotation.

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Optimal System Values for Producing a Large Velocity of the Distal Endpoint during Flail-Like Motion

Michele LeBlanc and Jesús Dapena

Equations that clarify the mechanical relationships between various parameter values and the velocity of the distal endpoint of a two-segment kinetic chain modeling the human arm were developed and analyzed. In particular, a single equation was presented that relates the distal endpoint velocity to the system’s angular momentum (as an indicator of muscular torque input), the ratio of the distal segment’s angular velocity to that of the proximal segment (the flail ratio), and the angle between the two segments (the configuration angle). These three system variables were analyzed to examine which values are best for creating a large value for the velocity of the distal endpoint. In addition, a sensitivity analysis was conducted to determine whether the relationships between the system values and the distal endpoint velocity were consistent for varying segment parameters. The relationships found were consistent for the various segment parameters. For any given values of the flail ratio and the configuration angle, the larger the value of the system angular momentum, the larger the value of the distal endpoint velocity. For any given values of the system angular momentum and the configuration angle, the larger the flail ratio, the larger the value of the distal endpoint velocity. For given values of the system angular momentum and the flail ratio, the optimal configuration angle that maximizes the distal endpoint velocity depends on the flail ratio value. While it may be impossible to generate simultaneously the combination of optimal parameter values determined, the knowledge of the relationships of these parameters with each other and with the distal endpoint velocity will aid in the search for an attainable optimal compromise.

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Dynamics of the Shoulder and Elbow Joints of the Throwing Arm during a Baseball Pitch

Michael Feltner and Jesús Dapena

Fastball pitches of eight intercollegiate varsity baseball pitchers were filmed using the direct linear transformation (DLT) method of three-dimensional cinematography. Coordinate data were obtained, and the resultant joint forces and torques at the shoulder and elbow joints were calculated. Various kinematic parameters were also calculated to help describe the motions of the shoulder and elbow joints throughout the pitch. At the instant of stride foot contact, a horizontal adduction torque was present at the shoulder joint, and the shoulder was externally rotating. After the onset of the horizontal adduction torque, abduction and internal rotation torques were also present at the shoulder joint and a varus torque was present at the elbow joint. After the instant of maximum external rotation (30 ms prior to ball release), the upper arm started to internally rotate, but it was still in a position of external rotation at the instant of release. This paper discusses the roles of the torques in producing the observed motions of the throwing arm.

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A Regression Analysis of High Jumping Technique

Jesús Dapena, Craig McDonald, and Jane Cappaert

It is difficult to ascertain for an individual high jumper the optimum values of the horizontal velocity and height of the center of mass at the end of the approach ran (VHO and H0, respectively) and of the activeness of the arms during the takeoff phase (AACT), because they depend on each athlete’s ability to resist buckling of the takeoff leg. However, the strongest jumpers will generally be those with the largest vertical elocity values at the end of the takeoff phase (VZ1). Therefore, VZ1 may serve as a rough indicator of a high jumper’s ability to resist buckling. This project derived equations that permit the use of the measured VZ1 value of a high jumper to predict what values should be expected for VHO, H0, and AACT. Comparison of the predicted and actual values of these parameters should help to diagnose the technique deficiencies of individual jumpers.

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Comparison of Film and Video Techniques for Estimating Three-Dimensional Coordinates within a Large Field

Rosa M. Angulo and Jesús Dapena

This study compared the errors produced with 3-D video and film analysis techniques using the DLT method with fixed cameras when the images cover a wide field of view. The results indicated that with a large field of view (8 meters) the accuracy of video analysis is clearly inferior to that of film analysis. However, within the volume of the control object, both film and video analyses are still precise enough for most practical purposes. Errors were larger in landmarks outside the control object than in the points of the control object. The maximum errors in the calculated positions of external landmarks were particularly large in the video analysis. However, even these rather large errors for points markedly outside the control object may be acceptable. It will depend on the requirements of each particular investigation.

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Effects of Wind and Altitude on the Times of 100-Meter Sprint Races

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.

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Three-Dimensional Interactions in a Two-Segment Kinetic Chain. Part I: General Model

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.

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The Effect of Muscular Pre-Tensing on the Sprint Start

Marcos Gutiérrez-Dávila, Jesús Dapena, and José Campos

Pre-tensed and conventional starts that exert, respectively, large and small forces against the starting blocks in the “set” position (0.186 vs. 0.113 N per newton of body weight) were analyzed. The starts were videotaped, and the horizontal forces exerted on feet and hands were obtained from separate force plates. In the pre-tensed start, the legs received larger forward impulses early in the acceleration (0.18 vs. 0.15 N·s per kilogram of mass in the first 0.05 s), but the hands received larger backward impulses (–0.08 vs. –0.04 N·s·kg–1). At the end of the acceleration phase, there was no significant difference in horizontal velocity between the two types of start and only trivial differences in the center of mass positions. The results did not show a clear performance change when the feet were pressed hard against the blocks while waiting for the gun.