An integrated qualitative analysis of overarm throwing.(Cover Story)
JOPERD--The Journal of Physical Education, Recreation & Dance; 8/1/1996; Morrison, Craig
The qualitative analysis of overarm throwing should be based on the principles of biomechanics, exercise physiology, motor development and sports psychology. The mechanics of overarm throwing based on its critical features includes an analysis of the angle of throwing, degree of muscular tension, leg drive, throwing position, coordination and arm rotation. The accurate sequential process of throwing will enhance the performance and skill of the athlete.
By applying an integrated model of qualitative analysis, teachers can give students specific, helpful cues that will lead to improved overarm throwing performance.
Qualitative analysis of motor skills must be based on information from many of the subdisciplines of physical education (biomechanics, exercise physiology, motor development, motor learning, pedagogy, sport psychology, etc.). These sources of information influence all four of the major tasks of qualitative analysis: preparation, observation, evaluation/diagnosis, and remediation [ILLUSTRATION FOR FIGURE 1 OMITTED]. First, professionals compile relevant information on the movement and on the performers to identify the critical features of the movement. Second, they systematically observe the movement to gather information on the status of the performance. The third task of qualitative analysis has two parts: the evaluation of the strengths and weakness of the performance, and the diagnosis of the most important correction. Fourth, the analyst provides one remedy or cue (feedback) based on the diagnosis that is likely to improve performance.
Qualitative analysis can then be defined as the systematic observation and introspective judgment of the quality of human movement for the purpose of providing the most appropriate remediation to improve performance. This definition and the circular model of qualitative analysis integrating the many subdisciplines of physical education (Knudson & Morrison, in press) are based on several models of qualitative analysis presented in the literature (Arend & Higgins, 1976; Hay & Reid, 1988; Hoffman, 1983; McPherson, 1990; Pinheiro, 1994). The purpose of this article is to show how an approach to qualitative analysis integrating many subdisciplines of physical education can be used to improve qualitative analysis of human movement.
The overarm throw is a critical fundamental movement pattern for many sports skills. The ability to qualitatively analyze the overarm throw is therefore a critical teaching and coaching skill. The following three examples will illustrate how an integrated qualitative analysis works.
Critical Features of the Overarm Throw
In preparing for a qualitative analysis of the overarm throw, professionals need to identify the critical features of the movement. Critical features are key features of a movement that are necessary for optimal performance. Critical features are identified based on the effectiveness in achieving the goal of the movement, the efficiency or economy of effort, and the prevention of injury to the performer. Research, professional literature, and experience all contribute to our understanding of the critical features of a movement.
Based on a wealth of research on the overarm throw, six critical features should be the focus of observation of the overarm throw. Table 1 pairs these critical features with examples of appropriate teaching cues. Teaching cues must be tailored to the cognitive level and skill level of each performer. Many scholars have proposed criteria for the qualitative analysis of overarm throwing (Jones-Morton, 1990; Kelly, Reuschein, & Haubenstricker, 1989; Morrison & Reeve, 1989; Roberton & Halverson, 1984), but most models have not presented a rationale for making diagnostic decisions in qualitative analysis. The six critical features of powerful overarm throwing are italicized in this section.
Overarm throwing should be evaluated based on the goal of the throw. The ball trajectory is largely determined by physical properties of the ball, ball speed, spin, and angle of release. For example, the optimal angles of projection for balls thrown for horizontal distance in most sport situations are between 35 and 42 degrees above the horizontal (Dowell, 1978). Many young baseball players throw the ball with a higher trajectory, decreasing the length of the throw and increasing the time spent covering the horizontal distance. Teachers need to evaluate the angle of release and trajectory of the ball to determine how the performer released the ball.
Skilled high-speed throwing requires differential relaxation of muscles at key instances so that other muscles and joints can contribute to the movement with minimal antagonistic resistance (Arend & Higgins, 1976; Broer, 1966; Scott, 1963). Analysts need to look for rigidity, limited range of motion, and facial expressions. High-speed throwing cannot be achieved with tense muscles because this tension limits other coordinated muscle and body actions.
Leg drive and opposition is the critical feature that combines the thrower's stance and step into the throw, setting up the later rotations of the body to provide a great deal of the power for the throw. Opposition is created by turning the non-throwing side of the body to the target. Leg drive or weight transfer occurs when the thrower pushes off the back leg and steps toward the target with the opposite foot. The forward step of mature high-speed throwers is usually greater than 50 percent of standing height (Roberton & Halverson, 1984). Research has shown that body rotation from good opposition contributes 40 to 50 percent of the ball speed, while the step contributes about 10 to 20 percent (Miller, 1980). A strong leg drive that transfers energy into body rotation is an essential technique point in high-speed throwing.
A strong throwing position involves keeping the upper arm at a right angle to the longitudinal axis of the spine (Plagenhoef, 1971). This position maximizes the speed transferred to the arm from the rotation of the trunk. Atwater (1979) found this 90-degree alignment to be a relatively invariant aspect of most throwing motions (overarm or sidearm). The throwing position and trunk lean at release should be observed from behind the thrower.
Sequential coordination is the precise coordination or timing of segment actions that can transfer energy to distal segments, greatly increasing their speed. The forward acceleration of a proximal segment eccentrically loads agonist muscles, and the later negative acceleration of the proximal segment uses segmental interactions to speed up the distal segment. This concept of a linked system of body segments has come to be known as the kinetic link or the kinetic chain (Steindler, 1955). The sequential action of the leg drive, hip rotation, spinal rotation, arm, and forearm/hand action are required to generate high-speed throws. This may be the most important feature in developing elite levels of overarm throwing. Unfortunately, the exact mechanism and direction of this kinetic link chain effect is not known (Phillips, Roberts, & Huang, 1983; Putnam, 1991).
The inward rotation of the upper arm and forearm are major propulsive and injury-protective actions in the overarm throw (Atwater, 1979). Coaches should know that inward rotation of the arm is the combination of humeral inward rotation, radio-ulnar pronation, and wrist flexion that provides the final push to the ball. A skilled arm action can generate 30 to 50 percent of ball speed in the over-arm throw (Miller, 1980). A great deal of energy is transferred up the body, and good timing of the forearm pronation and wrist flexion can create that additional pop, or great ball speed, of skilled throwers. Recent studies of the forces in baseball pitching have increased our understanding of the stresses overarm throwing places on the body (Feltner & Dapena, 1986; Fleisig, Andrews, Dillman, & Escamilla, 1995; Fleisig et al., 1996). Analysts should look for inward rotation of the arm in a long follow-through because this is a protective mechanism for shoulder and elbow injury.
Observation of Overarm Throwing
A good qualitative analysis of over-arm throwing should be based on the systematic observation of several trials from vantage points behind and beside the performer. A good rule of thumb is to observe at least five to eight trials from about 10 meters. Research has shown that it is important to have a systematic observational strategy to gather information for the qualitative analysis of human movement (Barrett, 1979; Hoffman, 1983). Such an approach can be organized into four phases:
The initial trials are observed for timing, rhythm, signs of tension, and the trajectory of the throws. This is a way to get an overall feeling about the performance.
The focus of observation is then shifted to the leg drive, opposition, and hip and trunk rotation.
The analyst observes the throwing position of the upper arm.
The analyst focuses attention on the sequential coordination of the throw. These fast actions of the trunk and arm are the most difficult to see and take the longest time to develop in performers.
Evaluation/Diagnosis and Remediation of Overarm Throwing
The throwing performances of three people will be used to illustrate an integrated qualitative analysis of the overarm throw. These drawings were taken from videotapes of actual performances. Readers should assume that the performances illustrated in this section were consistent across several trials.
Specifically, this section will focus on the two most difficult tasks of qualitative analysis of motor skills: evaluation/diagnosis and remediation. The child in figure 2 is throwing a baseball for maximum speed, the child in figure 3 is throwing a softball for maximum distance in a competition, and the adult in figure 4 is throwing a softball for speed and accuracy.
Table 1. Critical Features and Sample Cues for the Overarm Throw
Critical features Sample cues
Angle of release Throw flat.
Throw up an incline.
Relaxation Relax your upper body.
Leg drive and opposition Step with the opposite foot.
Turn your side to the target.
Strong throwing position Align the arm with your shoulders.
Sequential coordination Uncoil the body.
Inward rotation of the arm Roll the arm and wrist at release.
Evaluation of the performance illustrated in figure 2 suggests that this is good overarm throwing technique. Note the performer's opposition and strong transfer of weight into the throw. The upper arm is aligned with the shoulders, the ball is projected horizontally, and there is good inward rotation of the arm into a long follow-through. Since there are no major weaknesses, a good coach might use the subdiscipline of sport psychology to praise the performer, reinforcing his good technique and effort. The analyst might use his or her knowledge of motor learning to prescribe modified practice, perhaps increasing the difficulty of the throw by setting up a smaller or more distant target. Based on the discipline of motor development, the analyst may provide the practice that is needed to fine-tune the sequential coordination of high-speed throws.
Feedback encouraging loose and relaxed arm action may help this thrower continue to improve sequential coordination. An elite thrower's forearm is usually parallel to the ground when the trunk and upper arm have rotated to a position square with the target. Here the analyst might weigh the personal goals of the performer, time constraints, and prospects for physical training (exercise physiology) in selecting remediation.
Evaluation of the performance in figure 3 indicates that the child has good opposition and keeps his upper arm aligned. The analyst must, however, make a diagnosis of several weaknesses: the leg drive, the sequential coordination, and the angle of release. The performer is trying so hard that he exaggerates the step, but the weight transfer that can be channeled up the body into the throw is limited. The sequential coordination (simultaneous rotation of hip and trunk) of this child's throw is not yet mature, and the angle of release is too high.
The best remediation in this situation might be to correct the leg action in the throw. First, however, the thrower's effort or good aspects of the performance should be positively reinforced. As a general rule, analysts should avoid giving negative feedback messages like "Don't extend your left leg." Good correctional cues would focus on a smooth weight shift. A good leg drive would provide more energy that could be channeled into body rotation, the arm, and eventually the ball. A more forward thrust in this child's weight shift might also help pull the angle of release down. A good cue phrase might be "Push your weight forward from your right foot to your left."
Let's see why focusing on the weight shift could be the best remediation. The diagnosis of performance depends on the goal of the performance and the analyst's integration of the many sources of relevant information. Sequential coordination, the critical feature of many high-speed movements, is one of the last refinements in skilled performance. The development of sequential action will be limited until energy from the lower extremity can be channeled up the body. Cues to improve this critical feature should be saved for later.
Correcting the angle of release might initially improve performance because it is related to the goal (long throw) and is often an easy correction for a performer to make. It may not, however, be the best correction for this performer. If the angle of release is related to the child's step and subsequent loss of balance, the high release angle is a secondary error (Hoffman, 1983) that is symptomatic of the primary error (leg drive). Analysts should always try to relate actions to other actions in order to diagnose the cause of poor performance (Hay & Reid, 1988). This is one way of integrating biomechanics into the evaluation/diagnosis task of qualitative analysis.
The adult performer illustrated in figure 4 was a college athlete in a sport other than softball. Like many people, she has not reached a highly skilled pattern in her overarm throwing motor development. An analyst might first praise her strong throwing position or upper arm alignment. The analyst must then diagnose small weaknesses in two critical features - (1) leg drive and opposition and (2) sequential coordination.
One indication of poor sequential coordination is that the elbow and hand are well in front of the shoulder at release. Since much of the power channeled up the body by sequential coordination comes from opposition and leg drive, the best remediation may be to work on opposition and leg drive before sequential coordination. Examples of good cues may be "Turn your side to the target" and "Use that good leg drive by first turning sideways to the target, then stepping forward and powerfully rotating your trunk into the throw." It is not likely that good sequential coordination will develop without strong leg drive and opposition that transfers energy to the arm from the legs and trunk.
A coach could try to provide feedback to improve the sequential coordination of the throw. This is a difficult task. It is not appropriate to focus the athlete's attention on purposefully keeping the arm back during the propulsion phase of the throw, but it is appropriate to modify arm preparation early in the throwing action. The coach should praise effort, provide cues that reinforce vigorous trunk rotation and arm relaxation, and let the lag in the arm and forearm develop with practice. It is also a good idea to provide feedback on the distance of the goal ahead and the practice required to improve throwing coordination.
The best qualitative analyses involve an understanding of the four tasks of qualitative analysis and an integrated use of all subdisciplines of physical education. The examples in this article illustrate how an integrated qualitative analysis is used to provide feedback in correcting errors and motivating performers. There are no perfect approaches to teaching or qualitatively analyzing motor skills. However, a structured approach to qualitative analysis that integrates the many subdisciplines of physical education will increase the consistency and effectiveness of teaching motor skills.
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Duane Knudson is an assistant professor in the Department of Health, Human Performance and Recreation at Baylor University, Waco, TX 76798-7313. Craig Morrison is an associate professor in the Department of Physical Education at Southern Utah University, Cedar City, UT 84720.