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1.
The analysis of the joint kinematics during swimming plays a fundamental role both in sports conditioning and in clinical contexts. Contrary to the traditional video analysis, wearable inertial-magnetic measurements units (IMMUs) allow to analyse both the underwater and aerial phases of the swimming stroke over the whole length of the swimming pool. Furthermore, the rapid calibration and short data processing required by IMMUs provide coaches and athletes with an immediate feedback on swimming kinematics during training. This study aimed to develop a protocol to assess the three-dimensional kinematics of the upper limbs during swimming using IMMUs. Kinematics were evaluated during simulated dry-land swimming trials performed in the laboratory by eight swimmers. A stereo-photogrammetric system was used as the gold standard. The results showed high coefficient of multiple correlation (CMC) values, with median (first–third quartile) of 0.97 (0.93–0.95) and 0.99 (0.97–0.99) for simulated front-crawl and breaststroke, respectively. Furthermore, the joint angles were estimated with an accuracy increasing from distal to proximal joints, with wrist indices showing median CMC values always higher than 0.90. The present findings represent an important step towards the practical use of technology based on IMMUs for the kinematic analysis of swimming in applied contexts.  相似文献   

2.
Abstract

Kinematic analysis of swimming is of interest to improve swimming performances. Although the video recordings of underwater swimmers are commonly used, the available methodologies are rarely precise enough to adequately estimate the three dimensional (3D) joint kinematics. This is mainly due to difficulties in obtaining the required kinematic parameters (anatomical landmarks, joint centres and reference frames) in the swimming environment. In this paper we propose a procedure to investigate the right upper limb’s 3D kinematics during front crawl swimming in terms of all elbow and shoulder degrees of freedom (three rotations of the shoulder, two of the elbow). The method is based upon the Calibrated Anatomical Systems Technique (CAST), a technique widely used in clinics, which allows estimation of anatomical landmarks of interest even when they are not directly visible. An automatic tracking technique was adopted. The intra-operator repeatability of the manual tracking was also assessed. The root mean squared difference of three anatomical landmarks, processed five times, is always lower than 8 mm. The mean of the root mean squared difference between trajectories obtained with the different methodologies was found to be lower than 20 mm. Results showed that complete 3D kinematics of at least twice as many frames than without CAST can be reconstructed faster and more precisely.  相似文献   

3.
To evaluate the propulsive forces in front crawl arm swimming, derived from a three-dimensional kinematic analysis, these values were compared with mean drag forces. The propulsive forces during front crawl swimming using the arms only were calculated using three-dimensional kinematic analysis combined with lift and drag coefficients obtained in fluid laboratories. Since, for any constant swimming speed, the mean propulsive force should be equal to the mean drag force acting on the body of the swimmer, mean values of the calculated propulsive forces were compared with the mean drag forces obtained from measurements on a Measuring Active Drag (MAD) system. The two methods yielded comparable results, the mean difference between them being only 5% (2 N). We conclude that propulsive forces obtained from three-dimensional kinematic analysis provide realistic values. The calculation of the propulsive force appears to be rather sensitive to the point on the hand at which the velocity is estimated and less sensitive to the orientation of the hand.  相似文献   

4.
In the present research, we examined the effect of the starting and turning performances on the subsequent swimming parameters by (1) comparing the starting and turning velocities with the swimming parameters on the emersion and mid-pool segments and (2) by relating the individual behaviour of swimmers during the start and turns with subsequent behaviour on each swimming lap. One hundred and twelve 100 m performances on the FINA 2013 World Swimming Championships were analysed by an image-processing system (InThePool 2.0®). At the point of the start emersion, the swimming parameters of the 100-m elite swimmers were substantially greater than the mid-pool parameters, except on the breaststroke races. On the other hand, no diminution in the swimming parameters was observed between the turn emersion and the mid-pool swimming, except on the butterfly and backstroke male races. Changes on the surface swimming kinematics were not generally related to the starting or turning parameters, although male swimmers who develop faster starts seem to achieve faster velocities at emersion. Race analysts should be aware of a transfer of momentum when swimmers emerge from underwater with implications on the subsequent swimming kinematics, especially for male swimmers who employ underwater undulatory techniques.  相似文献   

5.
The main objective of this research was to develop a markerless optical motion capture system that can be used for daily use in swimming training. The butterfly stroke was targeted since it is considered bilaterally symmetric in motion. The system consisted of a segmentation process to obtain the participant’s silhouettes and a matching process to estimate the pose of the participant. A variable thresholding method was used to extract the silhouettes to solve non-uniform illumination in the recorded swimming video. Prior to the matching process, the human body was modeled as a series of nine segments to help the matching process. The model was then mapped so that it aligned with the silhouettes, which were investigated by similarity of intensity value. To minimize the degree of freedom in image matching, the available joint motion in the swimming human simulation model was used as a priori information for kinematics data of the swimming motion. As a result, the rotation angle’s correlation coefficients between the references and result of the matching process were around 0.95 for trunk, thigh, shank, upper arm, forearm, hand and 0.78 for head, hip and foot. The rotation angle and the velocity of the center of mass were put into the swimming human simulation model for a dynamics analysis. The simulation results show that the velocity obtained in the experiment corresponded to the fluid force exerted on the lower and upper limbs. Consequently, the proposed system of obtaining the joint motion of the butterfly stroke is suitable for daily training and coaching.  相似文献   

6.
游泳抓台式出发技术的运动学特征研究   总被引：2，自引：0，他引：2  
采用高速摄影方法,对12名男性大学生游泳运动员的游泳抓台式出发技术进行了运动学分析,揭示了抓台式出发技术的预备姿势、离台技术、重心移动以及入水技术的运动特征,为今后游泳抓台式出发技术的训练提供了有关参数。  相似文献   

7.
The undulatory underwater sequence is one of the most important phases in competitive swimming. An understanding of the recurrent vortex dynamics around the human body and their generation could therefore be used to improve swimming techniques. In order to produce a dynamic model, we applied human joint kinematics to three-dimensional (3D) body scans of a female swimmer. The flow around this dynamic model was then calculated using computational fluid dynamics with the aid of moving 3D meshes. Evaluation of the numerical results delivered by the various motion cycles identified characteristic vortex structures for each of the cycles, which exhibited increasing intensity and drag influence. At maximum thrust, drag forces appear to be 12 times higher than those of a passive gliding swimmer. As far as we know, this is the first disclosure of vortex rings merging into vortex tubes in the wake after vortex recapturing. All unsteady structures were visualized using a modified Q-criterion also incorporated into our methods. At the very least, our approach is likely to be suited to further studies examining swimmers engaging in undulatory swimming during training or competition.  相似文献   

8.
ABSTRACT

Ankle flexibility is critical to obtain a high swimming velocity in undulatory underwater swimming (UUS). The present study investigated the Froude (propelling) efficiency and three-dimensional (3D) kinematics of human UUS following the extrinsic restriction of the ankle by tape application. In Experiment 1, swimmers (9 male and 8 female college swimmers) performed UUS trials involving normal swimming (Normal) and swimming with tape application at the ankle (Tape). Kicking frequency was controlled in both settings. UUS kinematics were obtained with a two-dimensional motion analysis. Swimming velocity significantly decreased during swimming with tape application compared with that during normal swimming (Normal, 1.33 m·s?1; Tape, 1.26 m·s?1, p < 0.05). The Froude efficiency was not affected (Normal, 0.77; Tape, 0.76), and ankle plantar angle did not decrease during swimming (Normal, 159.02°; Tape, 160.38°). In Experiment 2, lower limb rotations of a male swimmer were analysed using 3D motion analysis under the same conditions as Experiment 1. An insufficient forefoot rotation was observed during downstroke kicks (the phase of the highest acceleration to forward direction). These findings suggest that UUS velocity is affected by the mobility of end effector.  相似文献   

9.
Adult overhead athletes without a history of shoulder injury show scapular adaptations. There is a lack of detailed assessment of scapular kinematics in junior overhead athletes. This study aims to investigate three-dimensional scapular kinematics in junior overhead athletes. We recruited a total of 20 junior tennis players and 20 healthy children without participation in any overhead sports in this study. Bilateral scapular kinematic data were recorded using an electromagnetic tracking device for scapular plane glenohumeral elevation. The data were further analysed at 30°, 45°, 60°, 90° and 120° during glenohumeral elevation and lowering. Statistical comparisons of the data between groups (junior overhead athletes and non-overhead athletes) and sides (serve dominant and non-dominant shoulders of the overhead athletes) were analysed with the ANOVA. Comparisons showed that, in general, the scapula was more upwardly rotated and anteriorly tilted in overhead athletes when compared to non-overhead athletes, however there was no side-to-side differences when serve dominant and non-dominant shoulders compared in junior overhead athletes. The serve dominant arm of junior overhead athletes had alternations in scapular kinematics when compared with the non-overhead athletes. These findings provide clinical evaluation implications and the need for clinicians to assess for potential adaptations in junior overhead athletes.  相似文献   

10.
The purpose of the study was to determine whether there are differences in kinematics between sprint and distance front crawl specialists when swimming at a distance pace using a six beat kick. Seven sprint and eight distance male specialists performed one maximum 400 m swim through a 6.75 m3 calibrated space recorded by six gen-locked cameras. The following variables were calculated: average swim velocity, stroke length, stroke frequency, upper limb and foot displacement, elbow angle, the shoulder and hip roll angle, duration of the stroke phases and time corresponding to particular events within the stroke cycle relative to hand entry. Differences between the groups were assessed by an independent t-test and effect size (d) calculations for each variable. The groups only differed significantly with respect to the average swim velocity, with the distance swimmers maintaining a greater velocity throughout the 400 m. However, effect sizes were moderate for elbow angle range during the pull phase (d = 0.78) and the total hip roll magnitude (d = 0.76). There was little evidence to suggest that sprint and distance swimmers using a six beat kick pattern differ in technique when swimming at a distance pace and therefore coaches should not encourage the development of different techniques between these groups.  相似文献   

11.
This study applied a vision-based tracking approach to the analysis of articulated, three-dimensional (3D) whole-body human movements. A 3D computer graphics model of the human body was constructed from ellipsoid solids and customized to two gymnasts for size and colour. The model was used in the generation of model images from multiple camera views with simulated environments based on measurements taken on each of three synchronized video cameras and the lighting sources present in the original recording environment. A hierarchical procedure was used whereby the torso was tracked initially to establish whole-body position and orientation and subsequently body segments were added successively to the model to establish body configuration. An iterative procedure was used at each stage to optimize each new set of variables using a score based on the RGB colour difference between the model images and video images at each stage. Tracking experiments were carried out on movement sequences using both synthetic and video image data. Promising qualitative results were obtained with consistent model matching in all sequences, including sequences involving whole-body rotational movements. Accurate tracking results were obtained for the synthetic image sequences. Automatic tracking results for the video images were also compared with kinematic estimates obtained via manual digitization and favourable comparisons were obtained. It is concluded that with further development this model-based approach using colour matching should provide the basis of a robust and accurate tracking system applicable to data collection for biomechanics studies.  相似文献   

12.
In order to measure active drag during front crawl swimming a system has been designed, built and tested. A tube (23 m long) with grips is fixed under the water surface and the swimmer crawls on this. At one end of the tube, a force transducer is attached to the wall of the swimming pool. It measures the momentary effective propulsive forces of the hands. During the measurements the subjects’ legs are fixed together and supported by a buoy. After filtering and digitizing the electrical force signal, the mean propulsive force over one lane at constant speeds (ranging from about 1 to 2 m s‐1) was calculated. The regression equation of the force on the speed turned out to be almost quadratic. At a mean speed of 1.55 m s‐1 the mean force was 66.3 N. The accuracy of this force measured on one subject at different days was 4.1 N. The observed force, which is equal to the mean drag force, fits remarkably well with passive drag force values as well as with values calculated for propulsive forces during actual swimming reported in the literature. The use of the system does not interfere to any large extent with normal front crawl swimming; this conclusion is based on results of observations of film by skilled swim coaches. It was concluded that the system provides a good method of studying active drag and its relation to anthropometric variables and swimming technique.  相似文献   

13.
游泳水槽动态阻力测量装置的研制   总被引：2，自引：0，他引：2  
在介绍国内、外游泳动态阻力现状研究的基础上，从理论上重新阐述了动态阻力和推进力的定义；确立了游泳水槽动态阻力测量装置的研究方案设计和技术路线；实现了游泳项目运动学和动力学参数的同步测试，为分析、诊断、优化游泳技术动作提供了有效的科研手段。  相似文献   

14.
Measurement of active drag during crawl arm stroke swimming   总被引：2，自引：0，他引：2  
In order to measure active drag during front crawl swimming a system has been designed, built and tested. A tube (23 m long) with grips is fixed under the water surface and the swimmer crawls on this. At one end of the tube, a force transducer is attached to the wall of the swimming pool. It measures the momentary effective propulsive forces of the hands. During the measurements the subjects' legs are fixed together and supported by a buoy. After filtering and digitizing the electrical force signal, the mean propulsive force over one lane at constant speeds (ranging from about 1 to 2 m s-1) was calculated. The regression equation of the force on the speed turned out to be almost quadratic. At a mean speed of 1.55 m s-1 the mean force was 66.3 N. The accuracy of this force measured on one subject at different days was 4.1 N. The observed force, which is equal to the mean drag force, fits remarkably well with passive drag force values as well as with values calculated for propulsive forces during actual swimming reported in the literature. The use of the system does not interfere to any large extent with normal front crawl swimming; this conclusion is based on results of observations of film by skilled swim coaches. It was concluded that the system provides a good method of studying active drag and its relation to anthropometric variables and swimming technique.  相似文献   

15.
Abstract

The purpose of the study was to determine whether there are differences in kinematics between sprint and distance front crawl specialists when swimming at a distance pace using a six beat kick. Seven sprint and eight distance male specialists performed one maximum 400 m swim through a 6.75 m3 calibrated space recorded by six gen-locked cameras. The following variables were calculated: average swim velocity, stroke length, stroke frequency, upper limb and foot displacement, elbow angle, the shoulder and hip roll angle, duration of the stroke phases and time corresponding to particular events within the stroke cycle relative to hand entry. Differences between the groups were assessed by an independent t-test and effect size (d) calculations for each variable. The groups only differed significantly with respect to the average swim velocity, with the distance swimmers maintaining a greater velocity throughout the 400 m. However, effect sizes were moderate for elbow angle range during the pull phase (d = 0.78) and the total hip roll magnitude (d = 0.76). There was little evidence to suggest that sprint and distance swimmers using a six beat kick pattern differ in technique when swimming at a distance pace and therefore coaches should not encourage the development of different techniques between these groups.  相似文献   

16.
The purpose of this study was to identify joint angular kinematics that corresponds to shooting accuracy in the stationary ice hockey wrist shot. Twenty-four subjects participated in this study, each performing 10 successful shots on four shooting targets. An eight-camera infra-red motion capture system (240 Hz), along with passive reflective markers, was used to record motion of the joints, hockey stick, and puck throughout the performance of the wrist shot. A multiple regression analysis was carried out to examine whole-body kinematic variables with accuracy scores as the dependent variable. Significant accuracy predictors were identified in the lower limbs, torso and upper limbs. Interpretation of the kinematics suggests that characteristics such as a better stability of the base of support, momentum cancellation, proper trunk orientation and a more dynamic control of the lead arm throughout the wrist shot movement are presented as predictors for the accuracy outcome. These findings are substantial as they not only provide a framework for further analysis of motor control strategies using tools for accurate projection of objects, but more tangibly they may provide a comprehensive evidence-based guide to coaches and athletes for planned training to improve performance.  相似文献   

17.
Breast displacement has been investigated in various activities to inform bra design, with the goal of minimising movement; however, breast motion during swimming has yet to be considered. The aim was to investigate trunk and breast kinematics whilst wearing varying levels of breast support during two swimming strokes. Six larger-breasted females swam front crawl and breaststroke (in a swimming flume), in three breast support conditions while three video cameras recorded the motion of the trunk and right breast. Trunk and relative breast kinematics were calculated. Greater breast displacement occurred mediolaterally in the swimsuit condition (7.8, s = 1.5 cm) during front crawl and superioinferiorly in the bare-breasted condition (3.7, s = 1.6 cm) during breaststroke, with the sports bra significantly reducing breast displacements. During front crawl, the greatest trunk roll occurred in the sports bra condition (43.1, s = 8.3°) and during breaststroke greater trunk extension occurred in the swimsuit condition (55.4, s = 5.0°); however, no differences were found in trunk kinematics between the three breast support conditions. Results suggest that the swimsuit was ineffective as a means of additional support for larger-breasted women during swimming; incorporating design features of sports bras into swimsuits may improve the breast support provided.  相似文献   

18.
The purpose of this study was to identify joint angular kinematics that corresponds to shooting accuracy in the stationary ice hockey wrist shot. Twenty-four subjects participated in this study, each performing 10 successful shots on four shooting targets. An eight-camera infra-red motion capture system (240 Hz), along with passive reflective markers, was used to record motion of the joints, hockey stick, and puck throughout the performance of the wrist shot. A multiple regression analysis was carried out to examine whole-body kinematic variables with accuracy scores as the dependent variable. Significant accuracy predictors were identified in the lower limbs, torso and upper limbs. Interpretation of the kinematics suggests that characteristics such as a better stability of the base of support, momentum cancellation, proper trunk orientation and a more dynamic control of the lead arm throughout the wrist shot movement are presented as predictors for the accuracy outcome. These findings are substantial as they not only provide a framework for further analysis of motor control strategies using tools for accurate projection of objects, but more tangibly they may provide a comprehensive evidence-based guide to coaches and athletes for planned training to improve performance.  相似文献   

19.
Tethered swimming is a method often used to measure or enhance the physical and technical resources of swimmers. Although it is highlighted that the technique used in tethered swimming is probably different from that used in free conditions, there are few comparative studies on this subject. The current study aims to compare fully tethered and free swimming based on kinematic hand parameters (orientation, velocity and acceleration of the hand, sweepback and angle of attack), which are known to act directly on the generation of propulsive forces. The results show that there are significant differences during the stretch and catch phases but less during the insweep and upsweep phases. Tethered swimming makes it possible to estimate the propelling forces generated by the hand in free swimming at distance and middle-distance paces, but overestimates it at sprint pace. However, in view of the modifications of the kinematic parameters, it should not be used under repeated conditions of use, such as for the development of swimmers’ capacity.  相似文献   

20.
By understanding the normal humeral and scapular kinematics during the kayak stroke, inferences about the relationship of kayaking technique and shoulder injury may be established. The purpose of this study was to describe scapular and humeral kinematics and to compare dominant versus nondominant symmetry in healthy whitewater kayakers performing the forward stroke. Twenty-five competent whitewater kayakers (mean age: 34.1 +/- 9.4 years, mean height: 1.768 +/- 0.093m, mean mass: 78.2 +/- 13.0 kg) underwent humeral and scapular kinematic assessment, using an electromagnetic tracking device, while kayaking on a kayak ergometer. Paired t-tests were used to determine symmetry. Scapular and humeral kinematic means and standard deviations at six time points during the kayak stroke were described. Scapular and humeral kinematics were shown to be similar upon bilateral comparison. The greatest potential for injury during the forward stroke may be at thrust paddle shaft vertical when the humerus is maximally elevated in internal rotation and adduction as subacromial structures may be mechanically impinged. The relationship between scapulohumeral kinematics related to injury at other time points are also described.  相似文献   

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