| Summary: | 碩士 === 國立臺中教育大學 === 體育學系碩士班 === 102 === Objectives: Badminton racquets come in three shapes that are more frequently seen, large, medium and small square head and two types of numbers of string holes, 72 and 76 holes, and their influences on the coefficients of restitution of badminton strings were compared for the purpose of racquet selection and design. The concrete objectives were as follows: I. the coefficients of restitution of different racquet shapes were compared; II. the coefficients of restitution of different numbers of string holes were compared. Method: First, six 23-pound badminton racquets with YY-BG65 strings were respectively fastened on a table with C-shaped clips. A shuttlecock launching machine would then serve shuttlecocks at a speed of 200 km/hr to hit against the central batting point (sweet spot) of the racquets. A 300Hz high speed camera was used to film the experiment in which 10 valid hits of each badminton racquet were obtained. Kwon3D motion analysis software was adopted to analyze the speeds of shuttlecocks before and after batting and to calculate their coefficients of restitution. The influences of racquet shapes and numbers of string holes on the coefficients of restitution were compared and analyzed with SPSS Statistics 20 and independent sample two-way ANOVA. When interaction effects were significant, their simple main effects were tested. However, when interaction effects were insignificant, their main effects were compared.Scheffe post hoc comparison was adopted, and the significant level was α＝.05. Results: I. Different racquet shapes and numbers of string holes had no interaction with the coefficients of restitution of badminton strings. II. Different racquet shapes and numbers of string holes did not create a significant difference to the coefficients of restitution of badminton strings (F=1.162, p=.320>.05). However, the mean of the coefficients of restitution was large square head>medium square head>small square head, whereas their variance was large square head<medium square head<small square head. III. Different numbers of string holes had significant influence on the coefficients of restitution of badminton strings (F=6.923, p=0.11<.05). IV. Survey of User Satisfaction: The bounce of a badminton racquet with 76 string holes was better than that with 72 string holes. The shuttlecock control of a badminton racquet with 72 string holes was better than that with 76 string holes. The shock absorption was large square head>medium square head>small square head. Conclusion: Different numbers of string holes had significant influence on the coefficients of restitution of badminton strings. The coefficient of restitution of a badminton racquet with 76 string holes was larger than that with 72 string holes. Although the coefficients of restitution of badminton racquets with different shapes did not create a significant difference, it showed that the coefficients of restitution and stability were large square head>medium square head>small square head after their mean and variance were analyzed. The information above can serve as references for badminton racquet selection and design.
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