speed kicking are all strongly influenced by the principles of range of motion, coordination, and segmental interaction. In addition, the force-motion, force-time, and optimal projection principles are important in kicking as well. The teacher might plan to keep the principles of inertia, spin, and balance in the back of their mind, so they will not be a focus of observation. These three principles are not likely to play a significant role in the kicking executed by most primary school children.
A child making a full-effort kick toward a goal is observed to consistently have a technique like that illustrated in Figure 9.1. Remember that good qualitative analysis requires the analyst to observe several performances so that clear trends of strengths and weaknesses can be identified, rather than jumping to conclusions or identifying unimportant "errors" (Knudson & Morrison, 2002). What critical features are strongly and weakly performed? These judgments are part of the evaluation process within the evaluation/diagnosis task of qualitative analysis.
The child illustrated in Figure 9.1 is clearly at a low developmental level of kicking. The teacher could praise the student's focus on the ball, strong approach, and balance during the kick. The list of bio-mechanical weaknesses is long at this beginning stage of learning. The biomechani-cal principles that are weakly incorporated into the kick are force-motion, optimal projection, inertia, range of motion, coordination, and segmental interaction. The student applies a suboptimal force to the ball because they plant the support foot well behind the ball, and impact the ball with their toe rather than the proximal instep (top of the shoelaces). Low-trajectory shots are desirable, but this kick, rolling along the ground, will slow the ball down as it rolls, making it easier for opponents to intercept. Finally, the student needs considerable
practice to increase the range of motion of the kick and to refine a well-timed sequential coordination that transfers energy through segmental interactions. Highly skilled kickers will approach the ball at an angle to increase the contralateral hip range of motion that can be sequentially combined with the hip and knee motions of the kicking leg. Which of these weaknesses do you think is most important to kicking success? One effective intervention strategy would be to provide a cue to plant their foot next to the ball. This is a simple correction that might be related to other weaknesses and might motivate the student with initial success and improvement.
Toward the end of the lesson you notice another child consistently kicking as in the sequence illustrated in Figure 9.2. What biomechanical principles are strongly or weakly performed in Figure 9.2?
The student depicted in Figure 9.2 is more skilled than the student from the pre vious example. Note the more vigorous approach to the ball. The intensity (inertia) of this approach is apparent in the length of the hurdle to the plant leg and the trunk lean used to maintain balance. It is hard to judge from the figure, but the ball is kicked at the desirable low trajectory. Some educators might conclude that all the biomechan-ical principles were well applied in this kick. The only two principles that might be slightly improved are range of motion and coordination. If the student were to approach the ball from a more oblique angle, the rotation of the pelvis on the left hip could be increased (range of motion) and combined (sequential coordination) with the good coordination of the kicking hip and knee.
Which of these small improvements, range of motion or coordination, do you think could be easily changed by this student in practice? Improvement in what principle would increase performance the
most? These are the issues that are important for a physical educator to examine in the diagnosis and intervention stages of qualitative analysis. The teacher might review some recent research and review papers on kicking (Barfield, 1998; Davids, Lees, & Burwitz, 2000; Dorge, Bull Andersen, Sorensen, & Simonsen, 2002). The following examples of qualitative analysis will illustrate the use of the biomechanical principles in these more difficult phases of qualitative analysis.
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