Soccer balls such as the Adidas Roteiro that have been used in soccer tournaments thus far had 32 pentagonal and hexagonal panels. Recently, the Adidas Teamgeist II and Adidas Jabulani, respectively having 14 and 8 panels, have been used at tournaments; the aerodynamic characteristics of these balls have not yet been verified. Now, the Adidas Tango 12, having 32 panels, has been developed for use at tournaments; therefore, it is necessary to understand its aerodynamic characteristics. Through a wind tunnel test and ball trajectory simulations, this study shows that the aerodynamic resistance of the new 32-panel soccer ball is larger in the high-speed region and lower in the middle-speed region than that of the previous 14- and 8-panel balls. The critical Reynolds number of the Roteiro, Teamgeist II, Jabulani, and Tango 12 was ~2.2 × 105 (drag coefficient, C d ≈ 0.12), ~2.8 × 105 (C d ≈ 0.13), ~3.3 × 105 (C d ≈ 0.13), and ~2.4 × 105 (C d ≈ 0.15), respectively. The flight trajectory simulation suggested that the Tango 12, one of the newest soccer balls, has less air resistance in the medium-speed region than the Jabulani and can thus easily acquire large initial velocity in this region. It is considered that the critical Reynolds number of a soccer ball, as considered within the scope of this experiment, depends on the extended total distance of the panel bonds rather than the small designs on the panel surfaces.

This study compared the basic aerodynamic characteristics of conventional volleyballs with those of new designs in a wind tunnel. Furthermore, to examine the aerodynamic instability near the critical Reynolds regime (14 m/s), balls were propelled with an impact-type ball ejection device and the variation in the coordinates of the landing point was measured. It was found that the critical Reynolds number for a conventional volleyball (Molten MTV5SLIT) was approximately 2.7 × 10⁵, whereas that for a design with honeycomb surface protrusions (Molten V5M5000) was slightly lower at approximately 2.2 × 10⁵. The honeycomb-type balls showed a drag coefficient of approximately 0.17 when supercritical, which is rather large compared with that of conventional balls (0.1). It is believed that the honeycomb surface protrusions increase the roughness of the ball surface, and this presumed increase in roughness implies a trend towards reduced aerodynamic instability close to critical Reynolds numbers.

The flight trajectory of a non-spinning or low-spinning soccer ball may fluctuate in unpredictable ways, with anomalous horizontal shaking or rapid falling. This “knuckling shot” is famously exploited by Cristiano Ronaldo in his free kicks. However, the technical aspects of kicking a knuckling shot are still unclear, and considerable analysis is required. In this study, we used high-speed video cameras to compare the knuckling shot with curve and straight shots. The results indicate that the angle of attack in the knuckling shot (3.3 ± 0.9°) was smaller than those in the straight and curve shots (19.3 ± 2.4°, 32.6 ± 3.9°, respectively). In sum, we demonstrated that in the knuckling shot, reduced angles of attack between the face and swing vectors at the impact surface and the primarily translational motions at ball impact are fundamental mechanisms.

The purpose of this study was to compare the basic aerodynamic characteristics of a previously developed 8-panel soccer ball with those of a new 32-panel soccer ball by conducting wind tunnel tests. Experimental results show that the critical Reynolds number (Re) was approximately 3.3 × 10⁵ for the 8-panel ball and approximately 2.4 × 10⁵ for the new ball, i.e., the Re of the new ball was slightly lower than that of the 8-panel ball. We conclude that the aerodynamic drag coefficient of the new 32-panel ball is closer to that of a golf ball than an 8-panel ball.

This study compares the male and female soccer players’ technical characteristics of ball impact and swing motion before the impact in instep kicks and inside kicks. High-speed video cameras and 3D motion capture were used to examine the characteristics and mechanics of the kicks. During both types of kick, the female players exhibited lower ball velocity, foot velocity immediately before the impact, striking mass, and average ball-to-foot velocity ratio than the male players. The ball-to-foot velocity ratio decreased as the distance of the impact point from the foot's centre of gravity increased. The results of this study suggested that when training female players it is important to instruct them how to impact the ball near the foot's centre of gravity under a variety of conditions. Moreover, the female players exhibited lower inclination of hip and thigh immediately before the impact compared to the male players.