Biomechanics is a diverse interdisciplinary field with branches in disciplines as varied as Zoology, Botany, Physical Anthropology, Orthopedics, Bioengineering and Human Performance. In all of these disciplines the general purpose of Biomechanics is the same: to understand the mechanical cause-effect relationships that determine the motions of living organisms. However, within each discipline Biomechanics tries to solve problems specific to that discipline: In Zoology, Botany and Physical Anthropology the main goal is the understanding of the relationships between structure and function; in Orthopedics and Bioengineering the main focus is also on structure and function, but with a special added emphasis on practical applications, such as the development of prosthetic devices. In Human Performance, Biomechanics contributes to the description, explanation, and prediction of the mechanical aspects of human exercise, sport and play.
Biomechanics research can be said to have two main facets within Human Performance: "basic science" and "applied science." In its basic science facet, Biomechanics tries to understand how the human body functions mechanically in a situation of maximum effort. When an athlete achieves a good performance, much of it depends on the fitness of the athlete (strength, quickness, endurance). But part of the value of the performance is also determined by the efficiency with which the body is used by the athlete. This efficiency can be improved through the coordination of the motions of different body parts in ways that permit the exertion of larger forces by the muscles, more appropriate timing of stretch reflex mechanisms, longer ranges of motion of certain limbs, etc. Thus, the value of a performance depends on the fitness of the athlete, but also on the technique used. The main objective of the basic science facet of biomechanics is to understand the cause-effect mechanisms that make some techniques better than others, and ultimately to find the optimum technique: what sequence of movements would lead to the best possible performance.
The basic science facet outlined above has an immediate bearing on applications: Once the optimum technique (or elements of it) are known, it should be possible to examine individual athletes, and determine what technique defects are preventing them from reaching their ultimate potential. Subsequent correction of these defects should lead to improved performance.
In the "direct approach" the researcher starts from causal factors (for instance, muscle tensions or ground reaction forces measured directly with a force plate), and subsequently calculates the accelerations, velocities and changes in location that result. An important subarea within the direct approach is computer simulation, in which the researcher makes hypothetical alterations in some of the causal factors, and finds out what effects these alterations would have had on the motions of the subject, and consequently on the value of the performance.
One of my two main lines of research is the mechanics of high jumping. The other one is my work on the mechanics of throwing events in track and field. I first started working primarily on the hammer throw, but I have now changed my emphasis to the discus throw. My ultimate goal is to reach a complete (or almost complete) understanding of the mechanisms involved in the techniques of these sport events. This will allow me to diagnose with a high degree of confidence the technique defects of individual athletes. The subsequent correction of these defects should lead to improved performance results and also to greater safety during the execution of the performance.
In a different facet of my work, I contribute to improve the methodology used for research in Biomechanics. I do not have a special interest in the development of methodology, but I have found it necessary for the advancement of my research on human motion itself. In the past, I have worked on the development of three-dimensional (3D) film analysis, and also on computer simulation methods. I am currently developing computer graphics applications. In the future, I plan to resume my work on computer simulation, because this methodology will probably be very useful for the study of the high jump takeoff.
My graduate students have been involved in some of my work on methodology. I have also contributed significantly to my students' research on human motion. My students' projects on human motion do not follow a single line of research, because each student has different interests. Still, the students' projects could be grouped into two categories: the study of flail-like motions, and an analysis of hurdling technique.
Today, the high jump is one of the sports activities that is best understood from a biomechanical standpoint. We now understand very well how the rotation over the bar is produced; the mechanisms involved in the run-up and takeoff are also much better understood than before, although not nearly as well as the bar clearance. In the future, I plan to complete the study of the airborne phase. After that, I will concentrate on the takeoff. I will use computer simulation as one of my main research tools to study the takeoff phase. I have done a lot of work in the simulation of airborne motions, but the simulation of the takeoff phase will be quite a different undertaking which will require a large amount of work in the development of new algorithms and computer programs.
(To see some interesting movies of the support foot during the takeoff phase of a high jump, go here; to see computer animations of a high jump and of an artificial high jump generated using computer simulation, go here.)
The beginning of the project was difficult. Unlike high jumping, which had always attracted researchers, biomechanical information on the hammer throw virtually did not exist. A variety of approaches had to be tried, to check what parameters would provide information leading to a better conceptual understanding of the event. The "pieces of the puzzle" finally fell in place. I found that the preliminary winds that the athlete makes in the back of the throwing circle during the early part of the throw, as well as the single-foot support phases that occur later on during the full turns are very important for the result. This contradicted the widely held belief of coaches that these parts of the throw do not contribute much to the distance of the throw. I also found that hammer throwers are unable to use a technique that coaches often recommend ("countering with the hips", which in theory should be advantageous) because it would require a tremendous amount of strength in a group of muscles (the latissimus dorsi) that throwers generally neglect in their training.
Through my work on the hammer throw, I gradually developed an interest in the discus throw, in which I am now concentrating much of my attention.
At this point I have completed a pilot study on the discus throw, based on a small group of subjects. The data show that the main interaction between the athlete and the ground occurs in the early part of the throw, while the main interaction between the athlete and the discus occurs in the late part of the throw. This specificity of purpose in the different parts of the throw was not known previously. Most coaches and athletes believe that the final part of the throw is the only important one, but my results indicate that the practitioners need to pay more attention to the early part of the throw, because it plays a key role in the generation of momentum for the combined athlete-plus-discus system. At this point the results are still preliminary, because they are based on a small number of subjects. My next step will be to repeat the study with a larger number of elite discus throwers. I have a grant from USA Track & Field to carry out this project in 1996.
A line of theoretical reasoning suggests that it would be beneficial to release the discus while the feet are still in contact with the ground, but many throwers release the discus after the feet have left the ground. After I complete the previous study, I will investigate the reasons for this apparent discrepancy between theory and practice in the discus throw.
(a: Film analysis methods)
In the early 1980's, our lab was one of the first to adopt a standard method for 3D film analysis (Abdel-Aziz & Karara's "Direct Linear Transformation" method) for regular use. Earlier, I had worked myself on the development of methodology for 3D film analysis. Together with one of my students (Rosa Angulo), I have also compared the accuracy of video-based versus film-based 3D analysis.
The development of 3D film analysis methodology is an area in which I am not currently working. I feel that this tool is already very useful in its present state of development, and that it is time to use it to investigate human motion, rather than to keep developing the methodology.
(f: Flail-like motions)
These reports start with a description of the optimum technique in high jumping. Then, numerical data and graphical information are used to describe the strong and weak aspects of each athlete's technique, and to give recommendations on possible changes that might lead to improvements in performance. Since 1994 the reports are accompanied by videotapes of solid-figure computer animations that explain to the athletes the defects in their techniques. The animations also show what the athletes' jumps would look like after the implementation of changes to correct the defects. The athletes can use these videotape animations to visualize the changes that they need to make in their techniques in order to improve performance.
This applied research work has been a good complement to our basic research. By following the development of top-caliber athletes from one year to the next, the technique alterations associated with changes in performance can be monitored, and this contributes to a better understanding of the cause-effect mechanisms of these sports events. In addition, many of our graduate students have gained valuable field experience.
The applied research activities go hand in hand with the publication of papers directed to coaches and athletes, my participation as a lecturer in clinics, and other activities that should be considered service rather than research.
Grant funding from USA Track & Field and the U.S. Olympic Committee (and in one occasion from the International Olympic Committee) has contributed to support these applied research projects. The help that our laboratory has provided to American athletes is appreciated by USA Track & Field and the U.S. Olympic Committee, and has greatly encouraged these sport governing bodies to provide us with grant funding to support not only our applied research but also our basic research. This is a valuable source of funding for us.
Last updated: December 2000
Copyright 1996, The Trustees of Indiana University