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1.
Abstract

The aim of this study was to examine the influence of leg kick on the pattern, the orientation and the propulsive forces produced by the hand, the efficiency of the arm stroke, the trunk inclination, the inter-arm coordination and the intra-cyclic horizontal velocity variation of the hip in sprint front crawl swimming. Nine female swimmers swam two maximal trials of 25 m front crawl, with and without leg kick. Four camcorders were used to record the underwater movements. Using the legs, the mean swimming velocity increased significantly. On the contrary, the velocity and the orientation of the hand, the magnitude and the direction of the propulsive forces, as well as the Froude efficiency of the arm stroke were not modified. The hip intra-cyclic horizontal velocity variation was also not changed, while the index of coordination decreased significantly. A significant decrease (13%) was also observed in the inclination of the trunk. Thus, the positive effect of leg kick on the swimming speed, besides the obvious direct generation of propulsive forces from the legs, could probably be attributed to the reduction of the body’s inclination, while the generation of the propulsive forces and the efficiency of the arm stroke seem not to be significantly affected.  相似文献   

2.
The aim of this study was to examine the effect of swimming speed on leg-to-arm coordination in competitive unilateral arm amputee front crawl swimmers. Thirteen well-trained swimmers were videotaped underwater during three 25-m front crawl trials (400 m, 100 m and 50 m pace). The number, duration and timing of leg kicks in relation to arm stroke phases were identified by video analysis. Within the group, a six-beat kick was predominantly used (n = 10) although some swimmers used a four-beat (n = 2) or eight-beat kick (n = 1). Swimming speed had no significant effect on the relative duration of arm stroke and leg kick phases. At all speeds, arm stroke phases were significantly different (P < 0.05) between the affected and unaffected sides. In contrast, the kicking phases of both legs were not different. Consequently, leg-to-arm coordination was asymmetrical. The instant when the leg kicks ended on the affected side corresponded with particular positions of the unaffected arm, but not with the same positions of the affected arm. In conclusion, the ability to dissociate the movements of the arms from the legs demonstrates that, because of their physical impairment, unilateral arm amputee swimmers functionally adapt their motor organisation to swim front crawl.  相似文献   

3.
We analysed stroke phases and arm and leg coordination during front crawl swimming with and without a wet suit. Twelve nationally and internationally ranked French male triathletes performed three swim trials in randomized order using the front crawl stroke with and without a wet suit. All triathletes swam at three different swim velocities, corresponding to the paces appropriate for the 800 m (V800), 100 m (V100) and 50 m (V50) events. The different stroke phases and arm and leg coordination were identified by video analysis. Arm coordination was quantified using a new index of coordination, which expresses the three major modalities of opposition, catch-up and superposition in swimming. At all swim velocities, no significant differences in leg movements with or without the wet suit were noted. However, the wearing of the wet suit was associated with a significantly greater stroke length at the paces appropriate for the 100 and 50 m events (+3.46% and +3.10% at V100 and V50, respectively; P<0.01); a significantly greater stroke index at all three velocities (+5.18%, +5.21% and +5.91% at V800, V100 and V50, respectively; P<0.01); a significantly shorter pulling phase (-10.97%; P<0.05) and lower index of coordination (-21.87%; P<0.01) at the pace appropriate for the 800 m; and a significantly greater entry and catch phase (+9.81%; P<0.05) at the pace appropriate for the 100 m. We conclude that the wet suit amplified the coordination mode of the triathletes (i.e. catch-up coordination) without modifying stroke rate, recovery phase or leg movements.  相似文献   

4.
ABSTRACT

The aim of this study was to propose a group of parameters able to quantify not only arm coordination but also inter limb coordination. These include the well know index of coordination with the relative duration of the stroke phases and two new parameters: the Index of synchronization (Ids) between arms and legs actions; and the Index of inter limb coordination (IdIC) calculated as the relative foot position during successive arm stroke phases. These parameters were compared between experts and amateur swimmers in a maximal front crawl sprint. The influence of arm stroke in leg kick parameters was also assessed, comparing the full stroke condition with a condition without arms actions. Sixty-five per cent of expert swimmers used synchronized limb actions while 95% of amateur swimmers used non-synchronized limb motions. These synchronized expert swimmers also converged towards a specific coordination pattern between foot position and arm stroke phases. In the condition without arms, both groups changed kick rate and amplitude. The present study reveals the interdependency of arms and legs actions and the importance of coordination and synchronization between limbs. Therefore, the proposed group of overall indexes of coordination provides a more complete marker for the analysis of swimming technique.  相似文献   

5.
We analysed stroke phases and arm and leg coordination during front crawl swimming with and without a wet suit. Twelve nationally and internationally ranked French male triathletes performed three swim trials in randomized order using the front crawl stroke with and without a wet suit. All triathletes swam at three different swim velocities, corresponding to the paces appropriate for the 800?m (V800), 100?m (V100) and 50?m (V50) events. The different stroke phases and arm and leg coordination were identified by video analysis. Arm coordination was quantified using a new index of coordination, which expresses the three major modalities of opposition, catch-up and superposition in swimming. At all swim velocities, no significant differences in leg movements with or without the wet suit were noted. However, the wearing of the wet suit was associated with a significantly greater stroke length at the paces appropriate for the 100 and 50?m events (+3.46% and +3.10% at V100 and V50, respectively; P?<0.01); a significantly greater stroke index at all three velocities (+5.18%, +5.21% and +5.91% at V800, V100 and V50, respectively; P?<0.01); a significantly shorter pulling phase (?10.97%; P?<0.05) and lower index of coordination (?21.87%; P?<0.01) at the pace appropriate for the 800?m; and a significantly greater entry and catch phase (+9.81%; P?<0.05) at the pace appropriate for the 100?m. We conclude that the wet suit amplified the coordination mode of the triathletes (i.e. catch-up coordination) without modifying stroke rate, recovery phase or leg movements.  相似文献   

6.
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   

7.
Front crawl swimmers often restrict the number of breaths they take during a race because of the possible adverse effects of the breathing action on resistance or stroke mechanics. The aim of this study was to determine whether differences exist in the kinematics of the trunk and upper extremity used during preferred-side breathing and breath-holding front crawl swimming. Six male swimmers performed trials at their 200 m race pace under breathing and breath-holding conditions. The underwater arm stroke was filmed from the front and side using video cameras suspended over periscope systems. Video recordings were digitized at 50 Hz and the three-dimensional coordinates of the upper extremity obtained using a direct linear transformation algorithm. Body roll angles were obtained by digitizing video recordings of a balsa wood fin attached to the swimmers' backs. The swimmers performed the breathing action without any decrement in stroke length (mean +/- s: breathing 2.24 +/- 0.27 m; breath-holding 2.15 +/- 0.22 m). Stroke widths were similar in the breathing (0.28 +/- 0.07 m) and breath-holding (0.27 +/- 0.07 m) trials, despite swimmers rolling further when taking a breath (66 +/- 5 degrees) than when not (57 +/- 4 degrees). The timing of the four underwater phases of the stroke was also unaffected by the breathing action, with swimmers rolling back towards the neutral position during the insweep phase. In conclusion, the results suggest that front crawl swimmers can perform the breathing action without it interfering with their basic stroke parameters. The insweep phase of the stroke assists body roll and not vice versa as suggested in previous studies.  相似文献   

8.
提高爬泳技术应重视爬泳双臂之间的相互作用。这相互作用有三：一是划水臂随身体的自然转动向前向外伸肩动作，会减小由另一臂空中移动时所造成的上体错误的左右摆动；二是在中长距离中，注意一手臂人水后的前伸动作，可增大划水距离，还有助于另一臂的推水效果；三是一臂的空中移动速度和人水速度的提高有助于另一臂划水效果的提高。  相似文献   

9.
The purpose of this study was to determine whether the Index of Coordination (IdC) and the propulsive phase durations can differentiate performance level during a maximal 400-m front crawl swim trial. Sixteen male swimmers constituted two groups based on performance level (G1: experts; G2: recreational). All participants swam the 400-m front crawl at maximal speed. Video analysis determined the stroke (swimming speed, stroke length, stroke rate) and coordination (IdC) parameters for every 50 m. Both stroke and coordination parameters discriminated performance level. The expert group had significantly higher values for speed and stroke length and lower values for the relative propulsive phase duration and IdC (p < .05). However there was no significant change in coordination parameters for either group throughout the trial. This suggests that, when associated with greater stroke length, catch-up coordination can be an efficient coordination mode that reflects optimal drag/propulsion adaptation. This finding provides new insight into swimmers' adaptations in a middle-distance event.  相似文献   

10.
Many coaches often instruct swimmers to keep the elbow in a high position (high elbow position) during early phase of the underwater stroke motion (pull phase) in front crawl, however, the high elbow position has never been quantitatively evaluated. The aims of this study were (1) to quantitatively evaluate the “high elbow” position, (2) to clarify the relationship between the high elbow position and required upper limb configuration and (3) to examine the efficacy of high elbow position on the resultant swimming velocity. Sixteen highly skilled and 6 novice male swimmers performed 25 m front crawl with maximal effort and their 3-dimensional arm stroke motion was captured at 60 Hz. An attempt was made to develop a new index to evaluate the high elbow position (Ihe: high elbow index) using 3-dimensional coordinates of the shoulder, elbow and wrist joints. Ihe of skilled swimmers moderately correlated with the average shoulder internal rotation angle (r = ?0.652, P < 0.01) and swimming velocity (r = ?0.683, P < 0.01) during the pull phase. These results indicate that Ihe is a useful index for evaluating high elbow arm stroke technique during the pull phase in front crawl.  相似文献   

11.
The aim of this study was to assess technical changes during constrained swimming in time-to-exhaustion tests. Ten swimmers of national standard performed a maximal 400-m front crawl and two sets of exhaustion tests at 95%, 100%, and 110% of mean 400-m speed. In the first set (free), swimmers had to maintain their speeds until exhaustion and mean stroke rate was recorded for each test. In the second set (controlled), the same speed and individual corresponding stroke rate were imposed. The durations of the exhaustion tests, relative durations of the stroke phases, and arm coordination were analysed. For each speed in the "controlled" set, the exhaustion tests were shorter. Moreover, variables were consistent, suggesting a stabilization of stroke technique. Under the free condition, stroke rate increased to compensate for the decrease in stroke length. At the same time, swimmers reduced the relative duration of their non-propulsive phases in favour of the propulsive phases. Thus, swimmers changed their arm coordination, which came close to an opposition mode. These two constraints enable swimmers both to maintain their stroking characteristics and develop compensatory mechanisms to maintain speed. Moreover, stroke rate can be seen as a useful tool for controlling arm technique during paced exercise.  相似文献   

12.
We examined the preferred mode of arm coordination in 14 elite male front-crawl swimmers. Each swimmer performed eight successive swim trials in which target velocity increased from the swimmer's usual 3000-m velocity to his maximal velocity. Actual swim velocity, stroke rate, stroke length and the different arm stroke phases were then calculated from video analysis. Arm coordination was quantified by an index of coordination based on the lag time between the propulsive phases of each arm. The index expressed the three coordination modes in the front crawl: opposition, catch-up and superposition. First, in line with the dynamic approach to movement coordination, the index of coordination could be considered as an order parameter that qualitatively captured arm coordination. Second, two coordination modes were observed: a catch-up pattern (index of coordination= -8.43%) consisting of a lag time between the propulsive phases of each arm, and a relative opposition pattern (index of coordination= 0.89%) in which the propulsive phase of one arm ended when the propulsive phase of the other arm began. An abrupt change in the coordination pattern occurred at the critical velocity of 1.8 m. s(-1), which corresponded to the 100-m pace: the swimmers switched from catch-up to relative opposition. This change in coordination resulted in a reorganization of the arm phases: the duration of the entry and catch phase decreased, while the duration of the pull and push phases increased in relation to the whole stroke. Third, these changes were coupled to increased stroke rate and decreased stroke length, indicating that stroke rate, stroke length, the stroke rate/stroke length ratio, as well as velocity, could be considered as control parameters. The control parameters can be manipulated to facilitate the emergence of specific coordination modes, which is highly relevant to training and learning. By adjusting the control and order parameters within the context of a specific race distance, both coach and swimmer will be able to detect the best adapted pattern for a given race pace and follow how arm coordination changes over the course of training.  相似文献   

13.
This paper reviews unsteady flow conditions in human swimming and identifies the limitations and future potential of the current methods of analysing unsteady flow. The capability of computational fluid dynamics (CFD) has been extended from approaches assuming steady-state conditions to consideration of unsteady/transient conditions associated with the body motion of a swimmer. However, to predict hydrodynamic forces and the swimmer’s potential speeds accurately, more robust and efficient numerical methods are necessary, coupled with validation procedures, requiring detailed experimental data reflecting local flow. Experimental data obtained by particle image velocimetry (PIV) in this area are limited, because at present observations are restricted to a two-dimensional 1.0 m2 area, though this could be improved if the output range of the associated laser sheet increased. Simulations of human swimming are expected to improve competitive swimming, and our review has identified two important advances relating to understanding the flow conditions affecting performance in front crawl swimming: one is a mechanism for generating unsteady fluid forces, and the other is a theory relating to increased speed and efficiency.  相似文献   

14.
We examined the preferred mode of arm coordination in 14 elite male front-crawl swimmers. Each swimmer performed eight successive swim trials in which target velocity increased from the swimmer's usual 3000-m velocity to his maximal velocity. Actual swim velocity, stroke rate, stroke length and the different arm stroke phases were then calculated from video analysis. Arm coordination was quantified by an index of coordination based on the lag time between the propulsive phases of each arm. The index expressed the three coordination modes in the front crawl: opposition, catch-up and superposition. First, in line with the dynamic approach to movement coordination, the index of coordination could be considered as an order parameter that qualitatively captured arm coordination. Second, two coordination modes were observed: a catch-up pattern (index of coordination?=??8.43%) consisting of a lag time between the propulsive phases of each arm, and a relative opposition pattern (index of coordination?=?0.89%) in which the propulsive phase of one arm ended when the propulsive phase of the other arm began. An abrupt change in the coordination pattern occurred at the critical velocity of 1.8?m?·?s?1, which corresponded to the 100-m pace: the swimmers switched from catch-up to relative opposition. This change in coordination resulted in a reorganization of the arm phases: the duration of the entry and catch phase decreased, while the duration of the pull and push phases increased in relation to the whole stroke. Third, these changes were coupled to increased stroke rate and decreased stroke length, indicating that stroke rate, stroke length, the stroke rate/stroke length ratio, as well as velocity, could be considered as control parameters. The control parameters can be manipulated to facilitate the emergence of specific coordination modes, which is highly relevant to training and learning. By adjusting the control and order parameters within the context of a specific race distance, both coach and swimmer will be able to detect the best adapted pattern for a given race pace and follow how arm coordination changes over the course of training.  相似文献   

15.
In this paper a video-based method to automatically track instantaneous velocities of a swimmer is presented. Single cameras were used to follow a marker (LED) attached to the body. The method is inspired by particle tracking techniques, traditionally used in the field of fluid dynamics, to measure local velocities of a fluid flow. During the validation experiment, a white LED was attached to the hip of a swimmer together with a speedometer. A swimmer performed four different stroke types. The velocity profiles using LED tracking were captured and showed less noise than the speedometer measurements. Only at times when the marker disappeared above the water surface due to body role in front crawl and backstroke swimming did the LED tracking fail to capture the athlete’s motion. The algorithm was tested in a 2D case with a single LED to illustrate the proof of principle, but should be suitable for implementation in a 3D analysis or multiple LED analysis.  相似文献   

16.
Abstract

The aim of this study was to assess technical changes during constrained swimming in time-to-exhaustion tests. Ten swimmers of national standard performed a maximal 400-m front crawl and two sets of exhaustion tests at 95%, 100%, and 110% of mean 400-m speed. In the first set (free), swimmers had to maintain their speeds until exhaustion and mean stroke rate was recorded for each test. In the second set (controlled), the same speed and individual corresponding stroke rate were imposed. The durations of the exhaustion tests, relative durations of the stroke phases, and arm coordination were analysed. For each speed in the “controlled” set, the exhaustion tests were shorter. Moreover, variables were consistent, suggesting a stabilization of stroke technique. Under the free condition, stroke rate increased to compensate for the decrease in stroke length. At the same time, swimmers reduced the relative duration of their non-propulsive phases in favour of the propulsive phases. Thus, swimmers changed their arm coordination, which came close to an opposition mode. These two constraints enable swimmers both to maintain their stroking characteristics and develop compensatory mechanisms to maintain speed. Moreover, stroke rate can be seen as a useful tool for controlling arm technique during paced exercise.  相似文献   

17.
In this study, we used recently developed technology to determine the force-time profile of elite swimmers, which enabled coaches to make informed decisions on technique modifications. Eight elite male swimmers with a FINA (Federation Internationale de Natation) rank of 900+ completed five passive (streamline tow) and five net force (arms and leg swimming) trials. Three 50-Hz cameras were used to video each trial and were synchronized to the kinetic data output from a force-platform, upon which a motorized towing device was mounted. Passive and net force trials were completed at the participant's maximal front crawl swimming velocity. For the constant tow velocity, the net force profile was presented as a force-time graph, and the limitation of a constant velocity assumption was acknowledged. This allowed minimum and maximum net forces and arm symmetry to be identified. At a mean velocity of 1.92+0.06 m s?1, the mean passive drag for the swimmers was 80.3+4.0 N, and the mean net force was 262.4+33.4 N. The mean location in the stroke cycle for minimum and maximum net force production was at 45% (insweep phase) and 75% (upsweep phase) of the stroke, respectively. This force-time profile also identified any stroke asymmetry.  相似文献   

18.
A new device was designed to measure the active drag during maximal velocity swimming based on the assumption of equal useful power output in two cases: with and without a small additional drag. A gliding block was used to provide an adjustable drag, which was attached to the swimmer and measured by a force transducer. Six swimmers of national standard (3 males, 3 females) participated in the test. For the males, the mean active drag ranged from 48.57 to 105.88 N in the front crawl and from 54.14 to 76.37 N in the breaststroke. For the females, the mean active drag ranged from 36.31 to 50.27 N in the front crawl and from 36.25 to 77.01 N in the breaststroke. During testing, the swimmer's natural stroke and kick were not disturbed. We conclude that the device provides a useful method for measuring and studying active drag.  相似文献   

19.
We examined the supposition that swimmers may exhibit an imbalance in bilateral arm power output during simulated swimming exercise. Ten competitive front crawl swimmers (5 males, 5 females; age 20.5+/-2.3 years; height 1.74+/-0.09 m; body mass 72.0+/-16.7 kg; 400 m freestyle swim time 278+/-20.5 s; mean +/- s) performed four incremental (10 W x min(-1)) swim ramp tests on a computer-interfaced biokinetic swim bench ergometer. External power output from each arm was measured continuously to exhaustion. The results showed that, throughout the course of the simulated swim, external power output clearly favoured the left arm (F1,9 = 12.5, P= 0.006). This was especially evident in the final 30 s to exhaustion, when 54.0+/-3.87% of external power output was derived from the left arm versus 46.0+/-3.87% from the right arm. The disparity in external power output was further highlighted when the participants were grouped into unilateral and bilateral breathers. Unilateral breathers (n = 5) produced 57.1+/-2.62% of external power output from the left armversus 42.9+/-2.62% from the right arm (P= 0.001). Bilateral breathers (n = 5) exhibited a more balanced external power output of 51.0+/-1.82% from the left arm and 49.0+/-1.82% from the right arm (P = 0.177). Evidence of power imbalance in the simulated swimming stroke may have important implications for optimizing swim performance. The observed power imbalance may be reduced when a bilateral breathing technique is adopted.  相似文献   

20.
The aim of this study was to assess the effect of the hand’s acceleration on the propulsive forces and the relative contribution of the drag and lift on their resultant force in the separate phases of the front crawl underwater arm stroke. Ten female swimmers swam one trial of all-out 25-m front crawl. The underwater motion of each swimmer’s right hand was recorded using four camcorders and four periscope systems. Anatomical landmarks were digitised, and the propulsive forces generated by the swimmer’s hand were estimated from the kinematic data in conjunction with hydrodynamic coefficients. When the hand’s acceleration was taken into account, the magnitude of the propulsive forces was greater, with the exception of the mean drag force during the final part of the underwater arm stroke. The mean drag force was greater than the mean lift force in the middle part, while the mean lift force was greater than the mean drag force in the final part of the underwater arm stroke. Thus, swimmers should accelerate their hands from the beginning of their backward motion, press the water with large pitch angles during the middle part and sweep with small pitch angles during the final part of their underwater arm stroke.  相似文献   

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