The previous qualitative analysis examples involved movements that must be matched to unpredictable environmental conditions. Motor learning classifies these movements as open skills, while skills with very stable conditions are called closed skills. When physical educators teach and analyze closed motor skills, they can be confident that performance is more strongly dependent on stereotypical technique rather than a variety of effective techniques. The standardized conditions of the free throw in basketball mean that the stereotypical techniques of a set shot would be optimal. Table 9.3 lists the key technique points and intervention cues that describe good free throw shooting technique.
Suppose an elementary school student is working on her free throw using modified equipment. Using a smaller ball and lower basket is critical to teaching good shooting technique with young children. At this age, they typically cannot employ good shooting technique using a regular ball and a 10-foot-high basket because of their lack of strength. Suppose that observations of the free throw attempts of a young child shows technique consistent with that illustrated in Figure 9.4. Identify the biomechanical principles that are strengths and weaknesses. Then diagnose the situation to determine what biomechan-ical principle should be the focus of any intervention.
The principles she can be complimented on are her good balance, simultaneous coordination, and spin on the ball. It is difficult to see in Figure 9.4, but this child used only one hand and one leg to shoot because she stepped into the shot. Weaknesses in her shooting technique are the limited use of range of motion and the force-time principles since she is not easily generating the ball speed needed for the shot. Another weakness is in the principle of optimal trajectory. Biomechanical research on shooting has shown that the optimal angles of projection for most set and jump shots are between 49 and 55° above the horizontal (Knudson, 1993). Young basketball players often select "flat" shooting trajectories, which actually require greater ball speed and often have angles of entry that do not allow the ball to pass cleanly through the hoop. This weighing of potential benefits of working on range of motion or initial shot trajectory is the essential diagnostic deci-
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