Published papers

It is considered to be very important to know both the speed and the spin of the ball of top players in tennis. Almost no research has been done on both speed and spin except for Muramatsu (2015, in Japanese), who reported about the service of top world-class players. However, we found no published reports of research on the forehand stroke. The present study focused on both the speed and the spin of the ball of 16 forehand strokes by the world number one male tennis player during competition, and examined their relationship. The ball speed data were obtained from the Hawk-Eye system, which archives ball-speed data from competitions. Ball spin was measured from shots taken with a high-speed camera shooting at 2000 fpm. The regression equation for calculating spin from ball speed was spin (rpm) = -33.2 x speed (km/h) + 7878. The average speed of the 16 forehand strokes was 132 km/h, and the average spin was 3486 rpm. These data may be useful indices for players aiming at improving their competitive power and for their coaches.

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.