Figure 5A. A scatter plot depicting the linear relationship between racquet vertical velocity before impact and ball topspin angular velocity. These variables were positively related (p < 0.01; r2 = 0.90), indicating that as racquet vertical velocity increased (i.e., a more vertical orientation), ball topspin angular velocity also increased. 5B. A scatter plot depicting the linear relationship between racquet head impact angle (i.e., open or closed racquet face) and ball topspin angular velocity. These two variables were negatively related (p < 0.01; r2 = 0.90), indicating that as racquet head impact angle decreased, ball topspin angular velocity increased.