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1.
The aim of this study was to determine the mechanical variables that govern success of the Hecht vault. The participants were 122 male gymnasts from 30 countries performing the vault at the 1995 World Gymnastics Championships. The vaults were filmed using a Photosonics 16-mm motion picture camera operating at 100 Hz. Approximately 80 frames were digitized for each vault analysed. The method of Hay and Reid was used to develop a theoretical model to identify the mechanical and physical variables that determine linear and angular motions of the vault. Correlational analysis was used to establish the strength of the relationship between the causal mechanical variables identified in the model and the judges' scores. Significant correlations (P ? 0.005) indicated that the following were important determinants of success: large horizontal and vertical velocities at take-off from the board and the horse; large vertical and angular distances of pre-flight; large vertical impulses of high force and short duration exerted on the horse and the resulting large changes in vertical velocity on the horse; and large horizontal and vertical distances and long times of post-flight. Of the 18 significant variables identified in the present study, the angular distance of pre- and post-flights, the horizontal velocity and angular momentum at take-off from the horse, and the average moment of inertia and duration of post-flight collectively accounted for 57% of the variation in the judges' scores.  相似文献   

2.
Abstract

The aim of this study was to determine the influence of run-up speed on take-off technique in the long jump. Seventy-one jumps by an elite male long jumper were recorded in the sagittal plane by a high-speed video camera. A wide range of run-up speeds was obtained using direct intervention to set the length of the athlete's run-up. As the athlete's run-up speed increased, the jump distance and take-off speed increased, the leg angle at touchdown remained almost unchanged, and the take-off angle and take-off duration steadily decreased. The predictions of two previously published mathematical models of the long jump take-off are in reasonable agreement with the experimental data.  相似文献   

3.
ABSTRACT

Chronic foot and ankle injuries are common in dancers; understanding how lower extremity loading changes in response to altered task goals can be beneficial for rehabilitation and injury prevention strategies. The purpose of this study was to examine mechanical demands during jump take-offs when the task goal was modified to focus on either increasing jump distance or increasing jump height. It was hypothesized that a jump strategy focused on height would result in decreased energetic demands on the foot and ankle joints. Thirty healthy, experienced female dancers performed saut de chat leaps while travelling as far as possible (FAR) or jumping as high as possible (UP). Ground reaction force (GRF) impulses and peak sagittal plane net joint moments and sagittal plane mechanical energy expenditure (MEE) of the metatarsophalangeal (MTP), ankle, knee, and hip joints were calculated. During take-off, vertical and horizontal braking GRF impulses were greater and horizontal propulsive GRF impulse was lower in the UP condition. MEE at the MTP, ankle, and hip joints was lower in UP, and MEE at the knee was higher in UP. These results suggest that a strategy focused on height may be helpful in unloading the ankle and MTP joints during dance leaps.  相似文献   

4.
The aim of this study was to determine the mechanical variables that govern success of the Hecht vault. The participants were 122 male gymnasts from 30 countries performing the vault at the 1995 World Gymnastics Championships. The vaults were filmed using a Photosonics 16-mm motion picture camera operating at 100 Hz. Approximately 80 frames were digitized for each vault analysed. The method of Hay and Reid was used to develop a theoretical model to identify the mechanical and physical variables that determine linear and angular motions of the vault. Correlational analysis was used to establish the strength of the relationship between the causal mechanical variables identified in the model and the judges' scores. Significant correlations (P < 0.005) indicated that the following were important determinants of success: large horizontal and vertical velocities at take-off from the board and the horse; large vertical and angular distances of pre-flight; large vertical impulses of high force and short duration exerted on the horse and the resulting large changes in vertical velocity on the horse; and large horizontal and vertical distances and long times of post-flight. Of the 18 significant variables identified in the present study, the angular distance of pre- and post-flights, the horizontal velocity and angular momentum at take-off from the horse, and the average moment of inertia and duration of post-flight collectively accounted for 57% of the variation in the judges' scores.  相似文献   

5.
The aim of this study was to establish the functions of the support leg in the long jump take-off with a three-element mechanical model spring, damper, and actuator The take-off motions of eleven male long jumpers, with personal bests from 6.45 to 7.99 m, were videotaped at 250 Hz and ground reaction forces were simultaneously recorded at 1 kHz. A two-dimensional 14-segment linked model was used to collect basic kinematic parameters. The spring, damper and actuator forces were determined from the displacement and velocity of the centre of mass and from ground reaction forces. Large spring and damper forces were exerted, and absorbed the impact force immediately after the touch-down. The spring force was also exerted from 25 to 75% of the take-off phase. The actuator force was dominant in the latter two-thirds of the take-off phase. Statistically significant correlations were found between the spring force impulse and the knee flexion during the take-off phase (r = 0.699, p < 0.05), and between the knee flexion and the angular velocity of the thigh at the touch-down (r = 0.726, p < 0.05). These results indicated that the jumper should retain less flexion of the take-off leg knee to increase the spring force, after a fast extension of the hip, and use a more extended knee at the touch-down to prevent excessive knee flexion.  相似文献   

6.
ABSTRACT

Previous research suggests that landing mechanics may be affected by the mechanics of the preceding jump take-off. The purpose of the present study was to investigate whether jump take-off mechanics influence the subsequent landing mechanics. Female volleyball (n = 17) and ice hockey (n = 19) players performed maximal vertical jumps with forefoot and heel take-off strategies. During forefoot and heel jumps, participants were instructed to shift their weight to their forefoot or heel, respectively, and push through this portion of the foot throughout the jump. Jump mechanics were examined using 3D motion analysis, where lower extremity net joint moment (NJM) work, NJM, and segment angles were compared between forefoot and heel jumps using multivariate ANOVA. During jump take-off, participants performed more positive ankle plantar flexor and knee extensor NJM work in forefoot compared to heel jumps (P < 0.05). From initial foot contact to foot flat, participants performed more negative ankle plantar flexor and hip extensor NJM work during heel compared to forefoot jumps (P < 0.05). The present results demonstrate that using a heel take-off strategy results in a different distribution of lower extremity NJM work and NJM during landing compared to landings following forefoot jumps.  相似文献   

7.
Abstract

In this study, we investigated the adjustments to posture, kinematic and temporal characteristics of performance made by lower limb amputees during the last few strides in preparation for long jump take-off. Six male unilateral trans-femoral and seven male unilateral trans-tibial amputees competing in a World Championships final were filmed in the sagittal plane using a 100-Hz digital video camera positioned so that the last three strides to take-off were visible. After digitizing using a nine-segment model, a range of kinematic variables were computed to define technique characteristics. Both the trans-femoral and trans-tibial athletes appeared to achieve their reduction in centre of mass during the flight phase between strides, and did so mainly by extending the flight time by increasing stride length, achieved by a greater flexion of the hip joint of the touch-down leg. The trans-tibial athletes appeared to adopt a technique similar to that previously reported for able-bodied athletes. They lowered their centre of mass most on their second last stride (?1.6% of body height compared with ?1.4% on the last stride) and used a flexed knee at take-off on the last stride, but they were less able to control their downward velocity at touch-down (?0.4 m · s?1). Both this and their restricted approach speed (8.9 m · s?1 at touch-down), rather than technique limitations, influenced their jump performance. The trans-femoral athletes lowered their centre of mass most on the last stride (?2.3% of body height compared with ?1.6% on the second last stride) and, as they were unable to flex their prosthetic knee sufficiently, achieved this by abducting their prosthetic leg during the support phase, which led to a large downward velocity at touch-down (?0.6 m · s?1). This, combined with their slower approach velocity (7.1 m · s?1 at touch-down), restricted their performance.  相似文献   

8.
Abstract

In this study, we compared mechanical factors in the reverse and three-inch power punches. Twelve expert male martial artists stood on a force plate, and executed reverse and power punches against a padded target fixed to a wall-mounted force plate. The force plates measured horizontal forces, and subsequently impulses and body centre of mass velocity changes. The motions of four markers attached to the arm were also collected, and were used to compute the horizontal velocities of the knuckle and of the arm centre of mass. The power punch produced smaller velocities immediately before impact than the reverse punch for the whole-body centre of mass (0.14 vs. 0.31 m · s?1), for the arm centre of mass (2.86 vs. 4.68 m · s?1), and for the knuckle (4.09 vs. 6.43 m · s?1). The peak force exerted by the fist was much smaller in the power punch than in the reverse punch (790 vs. 1450 N). However, the linear impulse exerted by the fist during the first 0.20 s of contact was slightly larger in the power punch than in the reverse punch (43.2 vs. 37.7 N · s). The results indicate that the power punch is less potent than the reverse punch, but slightly more effective for throwing the opponent off balance.  相似文献   

9.
ABSTRACT

This study examined the weightlifting load effects on the lower extremity coordination pattern during a snatch pull movement. Twenty male elite weightlifters performed snatch trials in each of the three load conditions [light (30%), medium (65%) and heavy (90%) of their maximum weightlifting capacities]. Kinematic data for the transition, second pull and take-off phases of a snatch were collected at 200 Hz using an eight-camera motion capture system. Angle-angle plots and coupling angles were calculated for further analyses. The results indicate that participants utilised knee flexion control-strategy in light and medium load conditions during the transition phase, but not for in-phase strategy in heavy load condition. In the second pull phase, participants utilised concurrent ankle dorsiflexion and knee extension, followed by hip extension strategy. The heavy load condition exhibited the distinct coordination strategies before knee extension. In the take-off phase, light and medium load conditions appeared to use thigh-phase strategy (right ankle-knee: p = 0.788, left: p = 0.035, right knee-hip: p = 0.012, left: p = 0.017, right ankle-hip: p = 0.029, left: p = 0.011). This suggests that the heavy load condition requires the use of two-joint coordination patterns (in-phase or anti-phase) as compared to the other lighter load conditions.  相似文献   

10.
This study investigated the effects of both anterior–posterior position and inclination of a back plate positioned on a starting platform on swimming start performance. Ten male college swimmers performed eight starts with varying combinations of take-off angle (normal and lower), inclination angle (10°, 25°, 45°, and 65°) and position (0.29, 0.44, and 0.59 m from the front edge of the starting block). Two-way repeated measures analysis of variance (ANOVA; take-off angle × back plate) for four conditions with take-off angles (normal and lower) and inclinations (10° and 45°), and one-way ANOVA for comparisons between four inclinations and three positions were carried out. Multiple comparisons were made using Bonferroni's method. The main effects of the take-off angle were on the vertical and resultant take-off velocities [F(1,18) = 36.72, p < 0.001 and F(1,18) = 9.58, p = 0.013, respectively]. Comparisons between the plate positions showed that the 5 m time of the 0.29 m condition was significantly longer, the take-off angle and vertical take-off velocity of the 0.59 m condition were significantly lower, and horizontal and resultant take-off velocities of the 0.29 m condition were significantly less. Rear foot take-off times were significantly longer in the ascending order: 0.29, 0.44, and 0.59 m.  相似文献   

11.
ABSTRACT

This study was designated to investigate the kinematical differences between successful and faulty spikes, in order to identify the best strategies leading to better spike performance. Simulating a real-game condition, 13 elite youth attackers performed 6 spikes in the presence of 2 blocks. The kinematic variables of the spike performances were recorded using 6 optoelectronic cameras (Vicon Motion systems, Oxford, UK). The paired sample t-test was used to compare the kinematic variables recorded during the delivery of successful and faulty spikes. Among the successful trials, both the angular velocities of the knees (≈12.4%) and hips (≈13.3%), and the vertical velocity of the centre of mass at take-off (≈6.5%) and arm swing (≈8.2%) were considerably higher during the plant phase. Consequently, the jump (≈4.3%) and spike (≈1.5%) heights, as well as the wrist velocity (≈5.5%), were significantly higher during the jump phase of successful spikes. In successful spike performances, the attackers adopted higher hip and knee angular velocities, combined with efficient arm swings, to produce higher take-off velocities and reach higher jump heights. This approach provides them with the better position regarding the ball and the blockers to find the best path and hit the ball with higher arm velocities.  相似文献   

12.
The 16 highest-scored Roche vaults (G1) performed during the 2000 Olympic Games were compared with those receiving the 16 lowest-scores (G2). A 16-mm motion picture camera operating at 100 Hz recorded the vaults during the competition. The results of t tests (p < .05) indicated G1, compared to G2, had (a) shorter time of board support, greater normalised average upward vertical force and backward horizontal force exerted by the board, greater change in the vertical velocity while on the board, and greater vertical velocity at board take-off, (b) comparable linear and angular motions in pre-flight, (c) smaller backward horizontal impulse exerted by the horse, smaller loss of the horizontal velocity while on the horse, and greater horizontal and vertical velocities at horse take-off, (d) greater height and larger horizontal distance of post-flight, (e) higher body mass centre at knee release, and (f) higher mass centre, greater normalised moment of inertia, and smaller vertical velocity at mat touchdown. Therefore, gymnasts and coaches should focus on sprinting the approach; blocking and pushing-off the take-off board rapidly and vigorously; departing the board with a large vertical velocity; exerting large downward vertical force and small forward horizontal force from the hand-stand position while on the horse; departing the horse with large horizontal and vertical velocities; and completing the majority of the double salto forward near the peak of trajectory and releasing the knees above the top of the horse to prepare for a controlled landing.  相似文献   

13.
Abstract

The purpose of this study was to examine relative timing, relative distance, and effector independence characteristics of the triple jump. We videotaped expert and novice triple jumpers using standing and running starts. On some trials, the triple jumpers were required to take off from their nondominant leg. Gentner's (1987) interaction test was used to assess the proportional duration model in describing the timing of the component submovements. For both experts and novices, the proportional durations varied with the type of start. For experts, the relative timing of the jump components was independent of the take-off leg. The findings were mixed for the novices. Similar results were obtained when relative distance was examined. These results are discussed with respect to constructs related to variability in skilled performance.  相似文献   

14.
Abstract

The objective of this study was to determine the relationship between different variables measured with a force plate during the swimming start push-off phase and start performance presented by times to 5, 10 and 15?m. Twenty-one women from the Slovenian national swimming team performed two different swim starts (freestyle and undulatory) on a portable force plate to a distance further than 15?m. Correlations between push-off variables and times to 5, 10 and 15?m were quantified through Pearson's product-moment correlation coefficient (r). The variables that significantly correlated (p?<?.05) to all times measured in the two starts performed were: average horizontal acceleration (freestyle: r?=??0.58 to ?0.71; and undulatory: r?=??0.55 to ?0.66), horizontal take-off velocity (freestyle: r?=??0.56 to ?0.69; and undulatory: r?=??0.53 to ?0.67) and resultant take-off velocity (freestyle: r?=??0.53 to ?0.65; and undulatory: r?=??0.52 to ?0.61). None of the variables derived from the vertical force were correlated to swimming start performance (p?>?.05). Based on the results of this study, we can conclude that horizontal take-off velocity and average horizontal acceleration (calculated as the average horizontal force divided by swimmer's body mass) are the variables most related to swimming start performance in experienced swimmers, and therefore could be the preferred measures to monitor swimmers’ efficiency during the push-off phase.  相似文献   

15.
Abstract

The aim of this study was to compare the somersaulting techniques used in the 16 highest-scoring and 16 lowest-scoring Roche vaults. Our hypothesis was that the gymnasts performing the highest-scoring Roche vaults would demonstrate a better technique than those performing the lowest-scoring Roche vaults while on the horse (pushing off the horse more effectively), somersaulting (executing most of the required somersaults higher in flight), and landing (showing a greater control). A 16-mm motion picture camera, operating at 100 Hz, recorded the vaults during the official competition. The two-dimensional direct linear transformation was used for spatial reconstruction. The results of t-tests (P < 0.05) indicated that, compared with the low-scoring gymnasts, the high-scoring gymnasts had: (1) greater height of body centre of mass and a more fully extended body position at the horse take-off; (2) greater height of body centre of mass at the peak of post-flight, knee release, and touchdown on the mat; (3) greater horizontal and vertical displacements of body centre of mass, greater somersaulting rotation, and longer time from the knee release to mat touchdown; and (d) markedly smaller landing point deductions. In conclusion, a successful Roche vault is likely when the focus is on: (a) leaving the horse with a large vertical velocity in an extended body position to achieve a high trajectory of centre of mass by first extending the legs, then immediately pushing off the horse vigorously, using the muscles of the upper extremity; (b) grasping the knees immediately after the take-off from the horse, achieving the tightly tucked body position early during the ascent to the peak, and completing two-thirds of the required somersaults at a great height; (c) releasing the knees and extending the body above the top level of the horse; and (d) contacting the mat with a high body centre of mass position.  相似文献   

16.
This study examines the hand and foot reaction force recorded independently while performing the kick-start technique. Eleven male competitive swimmers performed three trials for the kick-start with maximum effort. Three force platforms (main block, backplate and handgrip) were used to measure reaction forces during starting motion. Force impulses from the hands, front foot and rearfoot were calculated via time integration. During the kick-start, the vertical impulse from the front foot was significantly higher than that from the rearfoot and the horizontal impulse from the rearfoot was significantly higher than that from the front foot. The force impulse from the front foot was dominant for generating vertical take-off velocity and the force impulse from the rearfoot was dominant for horizontal take-off velocity. The kick-start’s shorter block time in comparison to prior measurements of the grab start was explained by the development of horizontal reaction force from the hands and the rearfoot at the beginning of the starting motion.  相似文献   

17.
ABSTRACT

Imitation jumps are frequently used in training for ski jumping. Yet, the dynamics of these jumps differ considerably. Thus, the relevance of imitation jumps for ski jumping performance is not elucidated. The aim of this study was to investigate the relationship between the technical execution of imitation jumps and ski jumping performance level. We compared the imitation jumps of 11 ski jumpers of different performance levels using a Spearman correlation transform of time traces of the kinetics (measured using force cells and motion capture) of imitation jumps. The kinetic aspects that were related to performance centred on the moment arm of ground reaction force to the centre of mass before the onset of the push-off, angular momentum early in push-off, thigh angle during the main period of push-off and vertical velocity towards the end of push-off. We propose that the thigh angle may be a key element allowing high development of linear momentum while preparing for appropriate aerodynamic position. Furthermore, the findings suggest that the kinetic development prior to (and during) push-off is more important than the kinematic end state at take-off.  相似文献   

18.
Abstract

When using a driver, the centre of pressure of a golfer shows a pattern that is characteristic of one of two distinct swing styles: the “front foot” style or the “reverse” style. The aim of this study was to establish whether these two swing styles are also evident when using other clubs, and if so, to determine whether golfers use the same swing style when using different clubs. Forty-six professional, amateur, and recreational golfers performed swings to hit a ball into a net placed 3 m away. Ten swings were performed for each of the driver, 3-iron, and 7-iron while standing on two force plates. The position of the golfer's centre of pressure parallel with the line of shot and relative to the feet was quantified at eight swing events that were identified from 200-Hz video. Cluster analysis confirmed that the front foot and reverse styles were evident in all three clubs, and most of the golfers (96%) used the same swing style for all three clubs. Golfers that used the reverse swing positioned their centre of pressure nearer to their toes at ball contact compared with golfers that used the front foot swing.  相似文献   

19.
Abstract

This study aimed to investigate the contributions of kinetic and kinematic parameters to inter-individual variation in countermovement jump (CMJ) performance. Two-dimensional kinematic data and ground reaction forces during a CMJ were recorded for 18 males of varying jumping experience. Ten kinetic and eight kinematic parameters were determined for each performance, describing peak lower-limb joint torques and powers, concentric knee extension rate of torque development and CMJ technique. Participants also completed a series of isometric knee extensions to measure the rate of torque development and peak torque. CMJ height ranged from 0.38 to 0.73 m (mean 0.55 ± 0.09 m). CMJ peak knee power, peak ankle power and take-off shoulder angle explained 74% of this observed variation. CMJ kinematic (58%) and CMJ kinetic (57%) parameters explained a much larger proportion of the jump height variation than the isometric parameters (18%), suggesting that coachable technique factors and the joint kinetics during the jump are important determinants of CMJ performance. Technique, specifically greater ankle plantar-flexion and shoulder flexion at take-off (together explaining 58% of the CMJ height variation), likely influences the extent to which maximal muscle capabilities can be utilised during the jump.  相似文献   

20.
Abstract

Two distinctly separate training facilities (dry-land and aquatic) are routinely used in springboard diving and pose an interesting problem for learning, given the inherent differences in landing (head first vs. feet first) imposed by the different task constraints. Although divers may practise the same preparation phase, take-off and initial aerial rotation in both environments, there is no evidence to suggest that the tasks completed in the dry-land training environment are representative of those performed in the aquatic competition environment. The aim of this study was to compare the kinematics of the preparation phase of reverse dives routinely practised in each environment. Despite their high skill level, it was predicted that individual analyses of elite springboard divers would reveal differences in the joint coordination and board-work between take-offs. The two-dimensional kinematic characteristics were recorded during normal training sessions and used for intra-individual analysis. Kinematic characteristics of the preparatory take-off phase revealed differences in board-work (step lengths, jump height, board depression angles) for all participants at key events. However, the presence of scaled global topological characteristics suggested that all participants adopted similar joint coordination patterns in both environments. These findings suggest that the task constraints of wet and dry training environments are not similar, and highlight the need for coaches to consider representative learning designs in high performance diving programmes.  相似文献   

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