論文

テニスにおいてトップ選手のボールの速度と回転量の両方を把握することは、大変重要なことであると考えられる。これまでボール速度と回転量の両方を報告している研究は殆どなく、我々の知る限り、村松ほか（2015）が世界トップクラス選手のサービスについて報告しているのが唯一の研究であり、フォアハンドグラウンドストロークについての報告は見当たらない。そこで我々は世界ランキング1位の男子テニス選手のフォアハンドグラウンドストロークについて、試合中のボール速度と回転量の両方に注目するとともに、両者の関係について考察した。ボール速度については、試合当日のサービス速度データを保管しているHawk-Eye社から提供を受けた。ボール回転量については高速度カメラで2000fpsにて撮影を行った。ボール速度から回転量を予測する回帰式は有意であり、回転量（rpm） = -33.2×速度（km/h） + 7878という関係が得られた。全16ショットの平均速度は132km/h、平均回転量は3486rpmであった。このデータは、競技力向上を目指す選手やそのコーチにとって、有用な指標となると考えられる。

We investigated the relationship between the speed and amount of spin of the serves of seven world-class tennis players. To estimate the amount of ball spin, we used a high-speed video camera running at 2000 frames per second to record the serves of those players in the matches of an international tennis tournament, played on a hard court surface. All of the studied players were placed in the world’s top 50 in either the year before the recorded matches or the year after. From the same matches, we obtained speed data as recorded by the Hawk-Eye system. For each player, we found a strong negative correlation between the serve speed and amount of spin. The average regression line using spin as the outcome variable (y; rpm) and speed as the predictor variable (x; km/h) was y = －56.4 x + 12954. We did not find any significant differences between the regression slopes or regression intercepts of the players. In addition, we did not find any significant dif-ferences between the regression slopes or regression intercepts between any one player’s first and second serves. The present study identifies target values for the speed and spin of a serve for players aiming to be-come top-ranked.

Focusing on students taking physical education classes in university, we conducted a preliminary study of two test conditions using Kikuchi's Social Skill Scale (KiSS-18) and the General Self-Efficacy Scale (GSES). The primary results of this study were as follows : 1) At the start of the first semester, we observed a significant difference between students who were 18–20 years of age and those who were 21 years of age in KiSS-18 and GSES scores, as well as a significant difference between 1st/2nd and 3rd year students, suggesting that both greater age and education level are related to higher scores on both measures. 2) In most subjects, KiSS-18 and GSES scores in the first semester were higher than the norm of these tests. 3) KiSS-18 scores tended towards a normal distribution, while GSES scores did not fall into a normal distribution. 4) Overall, KiSS-18 and GSES scores improved at the end of each semester, which we calculated by comparing the scores from the beginning and end of the first semester, and those from the beginning and end of the second semester. Students who took the classes in only one semester showed no improvement in scores from the beginning to the end of either semester. According to the above results, social skills and self-efficacy improved during the experiment according to age and amount of physical education training.