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1.
The purpose of this study was to measure the contributions of the motions of body segments and joints to racquet head speed during the tennis serve. Nine experienced male players were studied using three-dimensional film analysis. Upper arm twist orientations were calculated with two alternative methods using joint centres and skin-attached markers. The results showed that skin-attached markers could not be used to calculate accurate upper arm twist orientations due to skin movement, and that the use of joint centres produced errors of more than 20 degrees in the upper arm twist orientation when the computed elbow flexion/extension angle exceeded 135 degrees in the final 0.03 s before impact. When there were large errors in the upper arm twist orientation, it was impossible to obtain accurate data for shoulder or elbow joint rotations about any axis. Considering only the contributors that could be measured within our standards of acceptable error, the approximate sequential order of main contributors to racquet speed between maximum knee flexion and impact was: shoulder external rotation, wrist extension, twist rotation of the lower trunk, twist rotation of the upper trunk relative to the lower trunk, shoulder abduction, elbow extension, ulnar deviation rotation, a second twist rotation of the upper trunk relative to the lower trunk, and wrist flexion. The elbow extension and wrist flexion contributions were especially large. Forearm pronation made a brief negative contribution. Computed contributions of shoulder internal rotation, elbow extension and forearm pronation within the final 0.03 s before impact were questionable due to the large degree of elbow extension. Near impact, the combined contribution of shoulder flexion/extension and abduction/adduction rotations to racquet speed was negligible.  相似文献   

2.
The penalty throw in water polo: a cinematographic analysis   总被引：1，自引：0，他引：1  
Three-dimensional (3-D) high-speed cinematography was used to record the penalty throw in water polo by six elite male (M) and six elite female (F) players. The direct linear transformation technique (DLT) was used in the 3-D space reconstruction from 2-D images recorded via laterally placed phase-locked cameras operating at 200 Hz. Five of the twelve subjects lifted the ball from underneath at the start of the throw whilst the remaining subjects opted for a rotation lift. As the ball was brought behind the head the females used very little hip and shoulder rotation compared to the male players so that four of the six female subjects were square on to the target at the rear point. At the completion of the backswing the wrist was flexed to a similar angle (M-162 degrees; F-158 degrees); the elbow angle showed significantly greater flexion for females (85 degrees) than males (107 degrees). During the forward swing, from rear point to release, the wrist joint of the female players flexed from a rear point angle of 158 degrees to 148 degrees at release. The wrist movement for male subjects was different from the females in that it flexed from 162 degrees to 147 degrees, 0.10 s prior to release and then extended to 159 degrees at palmar release before again flexing to 156 degrees at release. The amount of elbow extension during the forward swing was 48 degrees for both groups; however, the females actually released the ball with the forearm vertical (89 degrees) compared to the male forearm angle of 78 degrees. Maximum angular velocity of the wrist and elbow occurred at release for 9 of the 12 subjects. Both the wrist and elbow joints (F-148 degrees; M-156 degrees at wrist and F-126 degrees; M-148 degrees at elbow) demonstrated greater flexion at release in female subjects, compared with males. Maximum linear endpoint velocities for the forearm and hand segments occurred at ball release resulting in mean ball velocities of 19.1 m s-1 and 14.7 m s-1 for male and female subjects respectively.  相似文献   

3.
Peak joint angles and joint angular velocities were evaluated for varying speed forehands in an attempt to better understand what kinematic variables are most closely related to increases in post-impact ball velocity above 50% of maximal effort. High-speed video was used to measure three-dimensional motion for 12 highly skilled tennis players who performed forehands at three different post-impact ball speeds: fast (42.7 +/- 3.8 m/s), medium (32.1 +/- 2.9 m/s), and slow (21.4 +/- 2.0 m/s). Several dominant-side peak joint angles (prior to ball impact) increased as post-impact ball speed increased from slow to fast: wrist extension (16%), trunk rotation (28%), hip flexion (38%), knee flexion (27%), and dorsiflexion (5%). Between the aforementioned peak joint angles and ball impact, dominant-side peak angular velocities increased as ball speed increased from slow to fast: peak wrist flexion (118%), elbow flexion (176%), trunk rotation (99%), hip extension (143%), knee extension (56%), and plantarflexion (87%). Most kinematic variables changed as forehand ball speed changed; however, some variables changed more than others, indicating that range of motion and angular velocity for some joints may be more closely related to post-impact ball speed than for other joints.  相似文献   

4.
Three‐dimensional (3‐D) high‐speed cinematography was used to record the penalty throw in water polo by six elite male (M) and six elite female (F) players. The direct linear transformation technique (DLT) was used in the 3‐D space reconstruction from 2‐D images recorded via laterally placed phase‐locked cameras operating at 200 Hz. Five of the twelve subjects lifted the ball from underneath at the start of the throw whilst the remaining subjects opted for a rotation lift. As the ball was brought behind the head the females used very little hip and shoulder rotation compared to the male players so that four of the six female subjects were square on to the target at the rear point. At the completion of the backswing the wrist was flexed to a similar angle (M‐162°; F‐158°); the elbow angle showed significantly greater flexion for females (85°) than males (107°).

During the forward swing, from rear point to release, the wrist joint of the female players flexed from a rear point angle of 158° to 148° at release. The wrist movement for male subjects was different from the females in that it flexed from 162° to 147°, 0.10 s prior to release and then extended to 159° at palmar release before again flexing to 156° at release. The amount of elbow extension during the forward swing was 48° for both groups; however, the females actually released the ball with the forearm vertical (89°) compared to the male forearm angle of 78°. Maximum angular velocity of the wrist and elbow occurred at release for 9 of the 12 subjects. Both the wrist and elbow joints (F‐148°; M‐156° at wrist and F‐126°; M‐148° at elbow) demonstrated greater flexion at release in female subjects, compared with males. Maximum linear endpoint velocities for the forearm and hand segments occurred at ball release resulting in mean ball velocities of 19.1 m s ‐1 and 14.7 m s‐ 1 for male and female subjects respectively.  相似文献   

5.
This study sought to identify kinematic differences in finger-spin bowling actions required to generate variations in ball speed and spin between different playing groups. A 12-camera Vicon system recorded the off-spin bowling actions of six elite and 13 high-performance spin bowlers, and the “doosra” actions of four elite and two high-performance players. Forearm abduction and fixed elbow flexion in the bowling arm were higher for the elite players compared with the high-performance players. The elite bowlers when compared with the high-performance players delivered the off-break at a statistically significant higher velocity (75.1 and 67.1 km/hr respectively) and with a higher level of spin (26.7 and 22.2 rev/s respectively). Large effect sizes were seen between ball rotation, pelvic and shoulder alignment rotations in the transverse plane. Elbow extension was larger for elite bowlers over the period upper arm horizontal to ball release. Compared to the off-break, larger ranges of shoulder horizontal rotation, elbow and wrist extension were evident for the “doosra”. Furthermore, the “doosra” was bowled with a significantly longer stride length and lower ball release height. Although not significantly different, moderate to high effect size differences were recorded for pelvis rotation, elbow extension and elbow rotation ranges of motion.  相似文献   

6.
Enhancing the understanding of coordination and variability in the tennis serve may be of interest to coaches as they work with players to improve performance. The current study examined coordinated joint rotations and variability in the lower limbs, trunk, serving arm and ball location in the elite female tennis serve. Pre-pubescent, pubescent and adult players performed maximal effort flat serves while a 22-camera 500 Hz motion analysis system captured three-dimensional body kinematics. Coordinated joint rotations in the lower limbs and trunk appeared most consistent at the time players left the ground, suggesting that they coordinate the proximal elements of the kinematic chain to ensure that they leave the ground at a consistent time, in a consistent posture. Variability in the two degrees of freedom at the elbow became significantly greater closer to impact in adults, possibly illustrating the mechanical adjustments (compensation) these players employed to manage the changing impact location from serve to serve. Despite the variable ball toss, the temporal composition of the serve was highly consistent and supports previous assertions that players use the location of the ball to regulate their movement. Future work should consider these associations in other populations, while coaches may use the current findings to improve female serve performance.  相似文献   

7.
Recreational tennis players tend to have higher incidence of tennis elbow, and this has been hypothesised to be related to one-handed backhand technique and off-centre ball impacts on the racket face. This study aimed to investigate for a range of participants the effect of off-longitudinal axis and off-lateral axis ball–racket impact locations on racket and forearm joint angle changes immediately following impact in one-handed tennis backhand groundstrokes. Three-dimensional racket and wrist angular kinematic data were recorded for 14 university tennis players each performing 30 “flat” one-handed backhand groundstrokes. Off-longitudinal axis ball–racket impact locations explained over 70% of the variation in racket rotation about the longitudinal axis and wrist flexion/extension angles during the 30 ms immediately following impact. Off-lateral axis ball–racket impact locations had a less clear cut influence on racket and forearm rotations. Specifically off-longitudinal impacts below the longitudinal axis forced the wrist into flexion for all participants with there being between 11° and 32° of forced wrist flexion for an off-longitudinal axis impact that was 1 ball diameter away from the midline. This study has confirmed that off-longitudinal impacts below the longitudinal axis contribute to forced wrist flexion and eccentric stretch of the wrist extensors and there can be large differences in the amount of forced wrist flexion from individual to individual and between strokes with different impact locations.  相似文献   

8.
Previous studies on overarm throwing have described a proximal-to-distal segmental sequence. The proximal segments reached their maximal linear velocities before the distal ones. In handball, no study has demonstrated this sequence from the upper torso to the wrist, although a recent study did present a different organization. The aim of this study was to analyse the throwing arm segmental organization during handball throwing. We found that the maximal linear velocity of the shoulder occurred after the maximal linear velocity of the elbow. Moreover, the maximal angular velocity of the upper torso occurred later than that of the elbow. Hence, contrary to other disciplines, the rotation of the upper torso was not suddenly stopped just after the forward arm motion was initiated. These results may apply to handball in general or be specific to the population of handball players studied. It may be advisable in future studies to include international players.  相似文献   

9.
The ability to generate a high racket speed and a large amount of racket kinetic energy on impact is important for table tennis players. The purpose of this study was to understand how mechanical energy is generated and transferred in the racket arm during table tennis backhands. Ten male advanced right-handed table tennis players hit topspin backhands against pre-impact topspin and backspin balls. The joint kinetics at the shoulder, elbow and wrist of the racket arm was determined using inverse dynamics. A majority of the mechanical energy of the racket arm acquired during forward swing (65 and 77% against topspin and backspin, respectively) was due to energy transfer from the trunk. Energy transfer by the shoulder joint force in the vertical direction was the largest contributor to the mechanical energy of the racket arm against both spins and was greater against backspin than against topspin (34 and 28%, respectively). The shoulder joint force directed to the right, which peaked just before impact, transferred additional energy to the racket. Our results suggest that the upward thrust of the shoulder and the late timing of the axial rotation of the upper trunk are important for an effective topspin backhand.  相似文献   

10.
The purpose of this study was to assess the contributions of racket arm joint rotations to the racket tip velocity at ball impact in table tennis topspin backhands against topspin and backspin using the method of Sprigings et al. (1994). Two cine cameras were used to determine three-dimensional motions of the racket arm and racket, and the contributions of the rotations for 11 male advanced table tennis players. The racket upward velocity at impact was significantly higher in the backhand against backspin than against topspin, while the forward velocity was not significantly different between the two types of backhands. The negative contribution of elbow extension to the upward velocity was significantly less against backspin than against topspin. The contribution of wrist dorsiflexion to the upward velocity was significantly greater against backspin than against topspin. The magnitudes of the angular velocities of elbow extension and wrist dorsiflexion at impact were both similar between the two types of backhands. Our results suggest that the differences in contributions of elbow extension and wrist dorsiflexion to the upward velocity were associated with the difference in upper limb configuration rather than in magnitudes of their angular velocities.  相似文献   

11.
The purpose of this study was to investigate the effect of the racket mass and the rate of strokes on the kinematics and kinetics of the trunk and the racket arm in the table tennis topspin backhand. Eight male Division I collegiate table tennis players hit topspin backhands against topspin balls projected at 75 balls · min?1 and 35 balls · min?1 using three rackets varying in mass of 153.5, 176 and 201.5 g. A motion capture system was used to obtain trunk and racket arm motion data. The joint torques of the racket arm were determined using inverse dynamics. The racket mass did not significantly affect all the trunk and racket arm kinematics and kinetics examined except for the wrist dorsiflexion torque, which was significantly larger for the large mass racket than for the small mass racket. The racket speed at impact was significantly lower for the high ball frequency than for the low ball frequency. This was probably because pelvis and upper trunk axial rotations tended to be more restricted for the high ball frequency. The result highlights one of the advantages of playing close to the table and making the rally speed fast.  相似文献   

12.
The purpose of this study was to examine the relationship between the upper limb anthropometric dimensions and a history of dominant upper limb injury in tennis players. Dominant and non-dominant wrist, forearm, elbow and arm circumferences, along with a history of dominant upper limb injuries, were assessed in 147 male and female players, assigned to four groups based on location of injury: wrist (n = 9), elbow (n = 25), shoulder (n = 14) and healthy players (n = 99). From anthropometric dimensions, bilateral differences in circumferences and in proportions were calculated. The wrist group presented a significant bilateral difference in arm circumference, and asymmetrical bilateral proportions between wrist and forearm, as well as between elbow and arm, compared to the healthy group (6.6 ± 3.1% vs. 4.9 ± 4.0%, P < 0.01; ?3.6 ± 3.0% vs. ?0.9 ± 2.9%, P < 0.05; and ?2.2 ± 2.2% vs. 0.1 ± 3.4%, P < 0.05, respectively). The elbow group displayed asymmetrical bilateral proportions between forearm and arm compared to the healthy group (?0.4 ± 4.3% vs. 1.5 ± 4.0%, P < 0.01). The shoulder group showed significant bilateral difference in elbow circumference, and asymmetrical bilateral proportions between forearm and elbow when compared to the healthy group (5.8 ± 4.7% vs. 3.1 ± 4.8%, P < 0.05 and ?1.7 ± 4.5% vs. 1.4 ± 4.3%, P < 0.01, respectively). These findings suggest that players with a history of injury at the upper limb joint present altered dominant upper limb proportions in comparison with the non-dominant side, and such asymmetrical proportions would appear to be specific to the location of injury. Further studies are needed to confirm the link between location of tennis injury and asymmetry in upper limb proportions using high-tech measurements in symptomatic tennis players.  相似文献   

13.
The purpose of this study was to determine the significance of mechanical energy generation and transfer in the upper limb in generating the racket speed during table tennis topspin forehands. Nine advanced and eight intermediate table tennis players performed the forehand stroke at maximum effort against light and heavy backspin balls. Five high-speed video cameras operating at 200 fps were used to record the motions of the upper body of the players. The joint forces and torques of the racket arm were determined with inverse dynamics, and the amount of mechanical energy generated and transferred in the arm was determined. The shoulder internal rotation torque exerted by advanced players was significantly larger than that exerted by the intermediate players. Owing to a larger shoulder internal rotation torque, the advanced players transferred mechanical energy from the trunk of the body to the upper arm at a higher rate than the intermediate players could. Regression of the racket speed at ball impact on the energy transfer to the upper arm suggests that increase in the energy transfer may be an important factor for enabling intermediate players to generate a higher racket speed at impact in topspin forehands.  相似文献   

14.
Previous studies on overarm throwing have described a proximal-to-distal segmental sequence. The proximal segments reached their maximal linear velocities before the distal ones. In handball, no study has demonstrated this sequence from the upper torso to the wrist, although a recent study did present a different organization. The aim of this study was to analyse the throwing arm segmental organization during handball throwing. We found that the maximal linear velocity of the shoulder occurred after the maximal linear velocity of the elbow. Moreover, the maximal angular velocity of the upper torso occurred later than that of the elbow. Hence, contrary to other disciplines, the rotation of the upper torso was not suddenly stopped just after the forward arm motion was initiated. These results may apply to handball in general or be specific to the population of handball players studied. It may be advisable in future studies to include international players.  相似文献   

15.
The aim of this study was to compare and evaluate the kinematics of baseball pitchers who participated in the 1996 XXVI Centennial Olympic Games. Two synchronized video cameras operating at 120 Hz were used to video 48 pitchers from Australia, Japan, the Netherlands, Cuba, Italy, Korea, Nicaragua and the USA. All pitchers were analysed while throwing the fastball pitch. Twenty-one kinematic parameters were measured at lead foot contact, during the arm cocking and arm acceleration phases, and at the instant of ball release. These parameters included stride length, foot angle and foot placement; shoulder abduction, shoulder horizontal adduction and shoulder external rotation; knee and elbow flexion; upper torso, shoulder internal rotation and elbow extension angular velocities; forward and lateral trunk tilt; and ball speed. A one-way analysis of variance (P ? 0.01) was used to assess kinematic differences. Shoulder horizontal adduction and shoulder external rotation at lead foot contact and ball speed at the instant of ball release were significantly different among countries. The greater shoulder horizontal abduction observed in Cuban pitchers at lead foot contact is thought to be an important factor in the generation of force throughout the arm cocking and arm acceleration phases, and may in part explain why Cuban pitchers generated the greatest ball release speed. We conclude that pitching kinematics are similar among baseball pitchers from different countries.  相似文献   

16.
Kinematic comparisons of 1996 Olympic baseball pitchers   总被引：1，自引：0，他引：1  
The aim of this study was to compare and evaluate the kinematics of baseball pitchers who participated in the 1996 XXVI Centennial Olympic Games. Two synchronized video cameras operating at 120 Hz were used to video 48 pitchers from Australia, Japan, the Netherlands, Cuba, Italy, Korea, Nicaragua and the USA. All pitchers were analysed while throwing the fastball pitch. Twenty-one kinematic parameters were measured at lead foot contact, during the arm cocking and arm acceleration phases, and at the instant of ball release. These parameters included stride length, foot angle and foot placement; shoulder abduction, shoulder horizontal adduction and shoulder external rotation; knee and elbow flexion; upper torso, shoulder internal rotation and elbow extension angular velocities; forward and lateral trunk tilt; and ball speed. A one-way analysis of variance (P < 0.01) was used to assess kinematic differences. Shoulder horizontal adduction and shoulder external rotation at lead foot contact and ball speed at the instant of ball release were significantly different among countries. The greater shoulder horizontal abduction observed in Cuban pitchers at lead foot contact is thought to be an important factor in the generation of force throughout the arm cocking and arm acceleration phases, and may in part explain why Cuban pitchers generated the greatest ball release speed. We conclude that pitching kinematics are similar among baseball pitchers from different countries.  相似文献   

17.
In this study, we examined the relationship between upper limb joint movements and horizontal racket head velocity to clarify joint movements for developing racket head speed during tennis serving. Sixty-six male tennis players were videotaped at 200 Hz using two high-speed video cameras while hitting high-speed serves. The contributions of each joint rotation to horizontal racket velocity were calculated using vector cross-products between the angular velocity vectors of each joint movement and relative position vectors from each joint to the racket head. Major contributors to horizontal racket head velocity at ball impact were shoulder internal rotation (41.1%) and wrist palmar flexion (31.7%). The contribution of internal rotation showed a significant positive correlation with horizontal racket head velocity at impact (r = 0.490, P < 0.001), while the contribution of palmar flexion showed a significant negative correlation (r = - 0.431, P < 0.001). The joint movement producing the difference in horizontal racket head velocity between fast and slow servers was shoulder internal rotation, and angular velocity of shoulder internal rotation must be developed to produce a high racket speed.  相似文献   

18.
The study investigated differences in the one- (SH) and two-handed (DH) backhands when hit flat, across-court (AC) and down-the-line (DL), and with heavy topspin DL (TDL). The ability to disguise each of these backhands when hitting the above strokes was also assessed. Eighteen college-level male tennis players, identified as having a high performance topspin SH (n = 6) or DH (n = 12) backhand drive, participated in the study. Players were required to hit three AC, DL and TDL backhands from the baseline with their preferred technique, while being filmed with two high-speed video cameras operating at 200 Hz. The highest horizontal velocity backhand for each stroke was analysed. Results indicated that the sequential coordination of five body segments (hips, shoulder, upper arm, forearm, and hand/racquet rotations) was required for the execution of the SH stroke. The same number of segments were generally coordinated in the DH stroke (hips, shoulders, and varying degrees of upper arm and forearm rotations followed by hand/racquet movement). Mature players produced comparable racquet horizontal velocities 0.005 s prior to impact using either the SH or DH backhand technique. The SH backhand was characterised by a more rotated shoulder alignment than the DH stroke (SH: 119.1 degrees; DH: 83.4 degrees) at the completion of the backswing. At impact the ball was impacted further in front (SH: 0.59 m: DH: 0.40 m) and a similar distance to the side of the body (SH: 0.75 m: DH: 0.70 m). Players using the DH backhand technique delayed the horizontal acceleration of the racquet towards the ball (SH: 0.13 s: DH: 0.08 s prior to impact) and thus were capable of displaying a similar hitting motion closer to impact than players with a SH technique.  相似文献   

19.
ABSTRACT

Knowledge of the kinematic differences that separate highly skilled and less-skilled squash players could assist the progression of talent development. This study compared trunk, upper-limb and racket kinematics between two groups of nine highly skilled and less-skilled male athletes for forehand drive, volley and drop strokes. A 15-camera motion analysis system recorded three-dimensional trajectories, with five shots analysed per participant per stroke. The highly skilled group had significantly (p < 0.05) larger forearm pronation/supination range-of-motion and wrist extension angles at impact than the less-skilled. The less-skilled group had a significantly more “open” racket face and slower racket velocities at impact than the highly skilled. Rates of shoulder internal rotation, forearm pronation, elbow extension and wrist flexion at impact were greater in the drive stroke than in the other strokes. The position of the racket at impact in the volley was significantly more anterior to the shoulder than in the other strokes, with a smaller trunk rotation angular velocity. Players used less shoulder internal/external rotation, forearm pronation/supination, elbow and wrist flexion/extension ranges-of-motions and angular velocities at impact in the drop stroke than in the other strokes. These findings provide useful insights into the technical differences that separate highly skilled from less-skilled players and provide a kinematic distinction between stroke types.  相似文献   

20.
Cricket     
The laws of bowling in cricket state ‘a ball is fairly delivered in respect of the arm if, once the bowler's arm has reached the level of the shoulder in the delivery swing, the elbow joint is not straightened partially or completely from that point until the ball has left the hand’. Recently two prominent bowlers, under suspicion for transgressing this law, suggested that they are not ‘throwing’ but due to an elbow deformity are forced to bowl with a bent bowling arm. This study examined whether such bowlers can produce an additional contribution to wrist/ball release speed by internal rotation of the upper arm. The kinematics of a bowling arm were calculated using a simple two‐link model (upper arm and forearm). Using reported internal rotation speeds of the upper arm from baseball and waterpolo, and bowling arm kinematics from cricket, the change in wrist speed was calculated as a function of effective arm length, and wrist distance from the internal rotation axis. A significant increase in wrist speed was noted. This suggests that bowlers who can maintain a fixed elbow flexion during delivery can produce distinctly greater wrist/ball speeds by using upper arm internal rotation.  相似文献   

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