Ball Spin Research Articles

Effect of vertical bat angle at impact on batted ball spin in baseball hitting

Effect of vertical bat angle at impact on batted ball spin in baseball hitting

Validation of ball spin estimates in tennis from multi-camera tracking data

ABSTRACTThe purpose of this study was to examine the accuracy of methods to estimate ball spin rate and spin axis direction using multi-camera tracking technology. The method implemented by Hawk-Eye and a theoretical ball trajectory model were assessed for their accuracy against high speed-vision. A theoretical ball trajectory model was found to estimate ball spin rate and the spin axis direction more accurately than the method used by Hawk-Eye. The superior performance of the ball trajectory model was indicated by a lower mean bias and standard deviation (2.92 ± 222.76) than Hawk-Eye (−100.01 ± 542.44), as well as narrower limits of agreement and a 327.63 RPM lower RMSE. Spin rates less than 4500 RPM were estimated with the highest accuracy, but neither method was able to consistently and accurately estimate spin rates >4500 RPM. The application of a trajectory model to multi-camera ball tracking data provides a practical and non-invasive method to accurately estimate the spin imparted when hitting, allowing for large-scale collection of spin rates during matches.

KINEMATIC PARAMETERS OF JUMP SHOT IN ELITE MALE BASKETBALL PLAYERS

The primary aim of this study was to determine kinematic parameters of jump shot in elite male basketball players, by analyzing the release time for shooting, the angle of entry, and ball spin and. The secondary aim of this study was to examine possible differences in these kinematic parameters among the players associated with their playing position. Eighteen male basketball players (7 guards, 8 forwards, 3 centers) from six Serbian senior teams were tested. 94Fifty basketball sensor was used to obtain the following kinematic parameters of jump shot). The highest average measured values of shot release time were found in centres (1.23±0.23 s) and the lowest in guards (1.07±0.28 s), although these differences were not statistically significant. Further, centres had a lower angle of entry (36.6±2.08°) than guards (40.54±4.76°) and forwards (42.05±3.77°). The highest value of backspin was obtained by forwards (130±11.91 rotations / min). There were no significant differences between guards, forwards and centers in any kinematic variables (p>.01). The relationship between the body height and angle of entry was not significant (p>0.05). In conclusion, compared to centers, guards and forwards showed similar results for the examined variables. This evidence seems to support the theory that compared to guards and forwards centres have the weaker shooting techniques. Coaches should encourage all players, especially centers, to shoot from all positions.

The effects of skill-level and playing-position on the anticipation of ball-bounce in rugby union

The ability to anticipate is a defining feature of skilled sports performance. To date, research investigating the information that underpins skilled anticipation has focused on kinematic information from an opponent and contextual factors. However, there has been a paucity of research investigating the influence of ball-flight and spin. Oval shaped balls, despite the seeming random nature, do in fact display specific bounce characteristics based on the nature of ball-flight. We tested the ability of 38 professional (categorised in to 15 ‘backs’ and 23 ‘forwards’ based on their playing position) and 20 less-skilled rugby union players to anticipate ball bounce direction for grubber and chip kicks using a temporal occlusion paradigm to restrict access to different sources of information. We predicted that skilled performers would have become attuned to both advance postural cues and the physical laws of ball flight and spin that govern ball bounce through their extensive practice and exposure to these situations, and so would anticipate more accurately than less-skilled performers. Results supported this hypothesis as skilled participants outperformed less-skilled in all occlusion conditions, however all groups anticipated more accurately with access to later emerging information sources (i.e., ball spin and rotation) with the skill level difference primarily underpinned by earlier available sources (i.e., advance postural cues). There was no difference between anticipation accuracy in professional forwards and backs and no kick type x group interaction, suggesting that the knowledge structures underpinning perceptual-cognitive expertise are not position specific. Findings have implication for models of anticipation and training design and tactics in rugby.

Spin experiments with a biased ball

Experimental and theoretical results are presented concerning spin and precession of a biased ball. The ball was biased by attaching a small ball to the top surface of a larger ball, and the balls were spun about a vertical axis. The small ball remained near the top of the large ball for up to about 60 s before falling slowly to a point below the equator of the large ball. The long-term stability of this arrangement appears to contradict previous observations with hurricane balls (two balls of equal mass joined together) that show that one ball cannot rise more than about twenty degrees above the equator of the other ball. The stability arises from the fact that the balls precessed about a vertical axis close to but not coincident with the centre of mass. Results are also presented for cases where (a) the small ball was observed to rise above the equator of the large ball, starting from a point below the equator and (b) the balls rolled about a horizontal axis while precessing about a remote vertical axis.

Speed and spin differences between the old celluloid versus new plastic table tennis balls and the effect on the kinematic responses of elite versus sub-elite players

This study measured 1) the speed and spin differences between the old celluloid versus new plastic table tennis balls at pre ball-table impact and post ball-table impact when projected with topspin at 7.56 m.s-1, and investigated 2) the effect this has on the kinematic responses of 5 elite versus 5 sub-elite players’ forehand topspin in response to topspin and backspin. Plastic balls were lower in both speed and spin at pre and post ball-table impact compared with celluloid balls but the magnitude of change in speed and spin for each ball material differed. During flight before impact, plastic balls lost 3.98% more speed and 1.24% more spin than celluloid balls. Post ball-table impact, plastic balls showed a greater speed increment (0.69%) and smaller spin decrement (0.19%) than celluloid balls. Differences in players’ kinematic responses to the different ball materials were found only when players returned backspin shots. Players supinated their rackets more by 2.23% at ball-racket contact and produced 3.37% less ball spin when returning plastic compared with celluloid balls; an indication of an early adaptation to the lower spin rate of plastic balls. The lack of differences in kinematic response to topspin may be due to the similar changes in speed and spin of both types of balls at ball-table impact. It is not known if a higher initial ball projection velocity would evoke differences in movement responses from the players post ball-table impact but could be explored in future studies.

Note on ‘Tracking the flight of a spinning football in three dimensions’

We make some crucial remarks about the recent presentation by Griffiths et al. considering their anomalous experimental results: The ball spin was observed to occasionally increase with time during its flight through the air. Possible reasoning due to experimental set-up and autorotation were given. Our results will be useful to sport education and relevant researchers.

The effect of uphill and downhill slopes on centre of pressure movement, alignment and shot outcome in mid-handicap golfers

ABSTRACT The aim of the study was to examine changes in centre of pressure (COP) movement, alignment and shot outcome during golf shots from flat, uphill, and downhill slopes by mid-handicap golfers. Twelve male golfers hit balls with a six-iron from the flat and 5° slopes while kinematics and kinetics of the swing were collected. A launch monitor measured performance outcomes. A shift in the COP was found during the backswing when playing on a slope, but disappeared during the downswing. Golfers attempted to align the body perpendicular to the slope at the start of the swing resulting in COP movement towards the lower foot, but were not able to maintain this throughout the swing, like low handicap golfers. There was no significant difference in stance width, but golfers placed the ball closer to the uphill foot on a slope. Ball speed was not significantly affected by the slope, but launch angle and ball spin were. Golfers were more likely to hit shots to the left from an uphill slope and to the right for a downhill slope. No consistent compensatory adjustments in alignment at address were found, with differences in final ball position due to lateral spin.

Passive range of motion of the hips and shoulders and their relationship with ball spin rate in elite finger spin bowlers

ObjectivesInvestigate rotational passive range of motion of the hips and shoulders for elite finger spin bowlers and their relationship with spin rate. DesignCorrelational. MethodsSpin rates and twelve rotational range of motion measurements for the hips and shoulders were collected for sixteen elite male finger spin bowlers. Side to side differences in the rotational range of motion measurements were assessed using paired t-tests. Stepwise linear regression and Pearson product moment correlations were used to identify which range of motion measurements were linked to spin rate. ResultsSide to side differences were found with more external rotation (p = 0.039) and less internal rotation (p = 0.089) in the bowling shoulder, and more internal rotation in the front hip (p = 0.041). Total arc of rotation of the front hip was found to be the best predictor of spin rate (r = 0.552, p = 0.027), explaining 26% of the observed variance. Internal rotation of the rear hip (r = 0.466, p = 0.059) and the bowling shoulder (r = 0.476, p = 0.063) were also associated with spin rate. ConclusionsThe technique and performance of elite finger spin bowlers may be limited by the passive range of motion of their hips and shoulders. The observed side to side differences may indicate that due to the repetitive nature of finger spin bowling adaptive changes in the rotational range of motion of the hip and shoulder occur.

Why some balls spin faster than others when they bounce

When a ball bounces obliquely on a horizontal surface, the bottom of the ball stretches horizontally and then vibrates backward. The resulting ball spin depends sensitively on the transverse vibration frequency. A simple model is presented to describe the effect, showing how the stored elastic energy can result in additional spin.

Assessment of the accuracy of different systems for measuring football velocity and spin rate in the field

The aim of this study was to measure the level of agreement of four portable football velocity and spin rate measurement systems (Jugs speed radar gun, 2-D high-speed video, TrackMan and adidas miCoach football) against a Vicon motion analysis system. One skilled male university football player performed 70 shots covering a wide range of ball velocities (12–30 m s−1) and spin rates (94–743 r/min). A Bland–Altman analysis was used to assess the level of agreement. For ball velocity, the 2-D high-speed video had the smallest systematic error, followed by the radar gun, TrackMan and miCoach football at 0.2, 0.4, 0.5 and 4.8 m s−1, respectively. A similar ranking was also observed for the random errors (95% confidence intervals: ±0.4, ±1.5, ±1.9 and ±6.0 m s−1). The first three systems all tracked ball velocity in >90% of shots, while the miCoach football tracked slightly fewer shots (79%). For spin rate, the miCoach football had a much smaller systematic error (4 vs 38 r/min) and random error (95% confidence intervals: ±24 vs ±355 r/min) compared to TrackMan. The miCoach also successfully tracked spin rate in more shots than the TrackMan (79% vs 44%). These results indicate that 2-D high-speed video would be the preferred option for the field assessment of ball velocity; however, radar gun and TrackMan may also be appropriate. A minimum of 10 frames of 2-D high-speed video, captured close to the ball starting position, was demonstrated to be sufficient in providing a reliable measure of ball velocity. The miCoach ball is the preferred option for field assessment of ball spin rate.

A joint kinetic analysis of rugby place kicking technique to understand why kickers achieve different performance outcomes

We aimed to identify differences in kicking leg and torso mechanics between groups of rugby place kickers who achieve different performance outcomes, and to understand why these features are associated with varying levels of success. Thirty-three experienced place kickers performed maximum effort place kicks, whilst three-dimensional kinematic (240 Hz) and ground reaction force (960 Hz) data were recorded. Kicking leg and torso mechanics were compared between the more successful (‘long’) kickers and two sub groups of less successful kickers (’short’ and ‘wide-left’) using magnitude-based inferences and statistical parametric mapping. Short kickers achieved substantially slower ball velocities compared with the long kickers (20.8 ± 2.2 m/s vs. 27.6 ± 1.7 m/s, respectively) due to performing substantially less positive hip flexor (normalised mean values = 0.071 vs. 0.092) and knee extensor (0.004 vs. 0.009) joint work throughout the downswing, which may be associated with their more front-on body orientation, and potentially a lack of strength or intent. Wide-left kickers achieved comparable ball velocities (26.9 ± 1.6 m/s) to the long kickers, but they were less accurate due to substantially more longitudinal ball spin and a misdirected linear ball velocity. Wide-left kickers created a tension arc across the torso and therefore greater positive hip flexor joint work (normalised mean = 0.112) throughout the downswing than the long kickers. Whilst this may have assisted kicking foot velocity, it also induced greater longitudinal torso rotation during the downswing, and may have affected the ability of the hip to control the direction of the foot trajectory.

Oblique impact of a spinning rubber ball

Measurements are presented on the oblique impact of a hollow rubber ball incident with spin on a polished granite surface. When incident with substantial backspin there is a large decrease in the horizontal ball speed and a large change in the spin of the ball. When incident with substantial topspin, there is only a small decrease in the horizontal speed and only a small change in ball spin. The impulse due to the friction force is therefore a strong function of the incident spin. The measured impulse determines if and when a transition from a sliding to a grip phase occurs. The line of action of the normal reaction force acts behind the centre of mass when the ball is incident with backspin, and ahead of the centre of mass when the ball is incident without spin or with topspin.

A Study on Quantification and Application of serve ball speed and spin rate in Japanese male Paralympian Wheelchair Tennis Players

A Study on Quantification and Application of serve ball speed and spin rate in Japanese male Paralympian Wheelchair Tennis Players

Control of ball spin rate by fingers torque during fastball and curveball pitches

Control of ball spin rate by fingers torque during fastball and curveball pitches

Three-dimensional batted ball in baseball: effect of ball spin on the flight distance

In this study, three-dimensional baseball kinematics are described including spin characteristics batted toward the left field (same field), center field, and right field (opposite field) in baseball. The study also discusses the effects of these kinematics on the flight distance. Six collegiate male baseball players performed free-batting and were instructed to hit the ball as far as possible. The balls just before, at, and after bat–ball impact were recorded with three high-speed video cameras. Eighty-one trials (same field: 25 trials, center field: 30 trials, and opposite field: 26 trials) were analyzed, and the ball kinematics among the three hitting directions were compared. Although there were no significant differences in the initial velocities and launch angles along the vertical plane of batted balls for the three hitting directions, the flight distance for the opposite field was significantly shorter than that for the other fields. The magnitude of the side spin components for the opposite field was significantly greater than that for the other fields. We conjecture that the balls batted toward the opposite field experienced a larger Magnus force along the horizontal direction; moreover, the trajectories were relatively more curved than in the cases towards the other fields. Therefore, a straight-line distance to the batted ball landing point in the opposite field tended to be shorter despite the similar initial velocity and launch angle. The results demonstrated that the spin characteristics, especially the side spin component, were different for different batting directions, and indicated that these characteristics affected the ball trajectory and flight distance.

Launch speed, angle and spin in golf

The impact of a golf club with a golf ball has previously been analysed by several authors, assuming that the ball rolls across the club face. In this paper it is shown that the ball grips the club face, rather than rolling, with the result that the outgoing ball spin is generally larger than previously estimated. Experimental results are presented for three different balls, showing that the ball spin can vary from one ball to the next, depending on the tangential coefficient of restitution of the ball.

The Effect of Uphill and Downhill Slopes on Weight Transfer, Alignment, and Shot Outcome in Golf.

The aim of the study was to examine changes in weight transfer, alignment, and shot outcome during golf shots from flat, uphill, and downhill slopes. Twelve elite male golfers hit 30 shots with a 6-iron from a computer-assisted rehabilitation environment used to create 5° slopes while collecting 3-dimensional kinematics and kinetics of the swing. A launch monitor measured performance outcomes. A shift in the center of pressure was found throughout the swing when performed on a slope, with the mean position moving approximately 9% closer to the lower foot. The golfers attempted to remain perpendicular to the slope, resulting in weight transfer toward the lower foot. The golfers adopted a wider stance in the sloped conditions and moved the ball toward the higher foot at address. Ball speed was not significantly affected by the slope, but launch angle and ball spin were. As the coaching literature predicted, golfers were more likely to hit shots to the left from an uphill slope and to the right from a downhill slope. No consistent compensatory adjustments in alignment at address or azimuth were found, with the change in final shot dispersion resulting from the lateral spin of the ball.

Wind Turbine Bearing Diagnostics Based on Vibration Monitoring

Reliability maintenance can be considered as an accurate condition monitoring system which increasing beneficial and decreasing the cost production of wind energy. Supporting low friction of wind turbine rotating shaft is the main task of rolling element bearing and it is the main part that suffers from failure. The rolling failures elements have an economic impact and may lead to malfunctions and catastrophic failures. This paper concentrates on the vibration monitoring as a Non-Destructive Technique for assessing and demonstrates the feasibility of vibration monitoring for small wind turbine bearing defects based on LabVIEW software. Many bearings defects were created, such as inner race defect, outer race defect, and ball spin defect. The spectra data were recorded and compared with the theoretical results. The accelerometer with 4331 NI USB DAQ was utilized to acquiring, analyzed, and recorded. The experimental results were showed the vibration technique is suitable for diagnostic the defects that will be occurred in the small wind turbine bearings and developing a fault in the bearing which leads to increasing the vibration amplitude or peaks in the spectrum.

IoT Platform for Sports Analytics

This paper is an experience report on IoT platforms for sports analytics. In our prior work [11], we proposed iBall, a system that explores the possibility of bringing IoT to sports analytics, particularly to the game of Cricket. iBall develops solutions to track a ball's 3D trajectory and spin with inexpensive sensors and radios embedded in the ball. Towards this end, iBall performs fusion of wireless and inertial sensory data and integrates them into physics-based motion models of a ball in flight. The median ball location error is at 8cm while rotational error remains below 12° even at the end of the flight. The results do not rely on training, hence we expect the core techniques to extend to other sports like baseball, with some domain-specific modifications.