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Copyright of Dirasat: Educational Sciences is the property of University of Jordan and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Recently, a commercially available starting 'ledge' designed to reduce foot slippage during the execution of the backstroke start was introduced in competit ive swimming. For the purpose of identifying potential safety consequences, the present study investigated the effect of ledge use on head depths, speeds, and distances in backstroke starts of athletes with no prior or only novice familiarity of the ledge. Competitive backstroke starts were performed with and without ledges by high school-aged (14.5 to 19.2 yr, N = 61) swimmers in 1.52 m of water during a closed testing session. A SIMI Reality Motion System in a calibrated space using three cameras was employed for filming starts. Dependent measures were initia l head height (Yset), distance from wall at entry (Xentry), entry angle (Angleentry), horizontal velocity at head entry (XVelentry), resultant velocity at entry (ResVelentry), maximum depth of the center of the head (Ymhd), resultant velocity at maximum head depth (ResVelmhd), and distance from the wall at maximum head depth (Xmhd). The ledge (L) condition showed significant increases compared to the non-ledge (NL) condition in Xent ry (L 1.61 ± 0.59 m, NL 1.50 ± 0.53 m, p < .001), ResVelent ry (L 3.44 ± 0.97 m·s-1, NL 3.08 ± 1.00 m·s-1, p < .001), Angleent ry (L 43.13 ± 16.97, NL 39.66 ± 18.11, p = .030), Xmhd (L 4.18 ± 0.58 m, NL 4.09 ± 0.63 m, p = .008), and Ymhd (L 0.54 ± 0.21 m, NL 0.49 ± 0.18, p <.001). Backstroke starts using the ledge modestly affected 5 of 8 dependent measures in a direction arguably associated with an increased risk to the novice swimmer. [ABSTRACT FROM AUTHOR]

Purpose. Resisted and assisted in-water training methods are often employed in swimming training but their effectiveness remains unsubstantiated for different strokes and age groups. The study aim was to quantify the effects of a 3-week combined assisted and resisted in-water training program on 50- and 100-m adolescent backstroke performance. Methods. In addition to regular swimming training, 9 (5 male, 4 female; age: 15.4 ± 1.7 years; 50-m backstroke FINA points: 346 ± 142) competitive backstroke swimmers performed a combined in-water machine-resisted and bungee-assisted training program 3 days/week with 3 resisted and 3 assisted 25-m sprints per session. Before and after the 3-week training, 50- and 100-m backstroke time trials were undertaken, with stroke rate, heart rate, and rating of perceived exertion collected. Results. There was a significant small improvement in 100-m backstroke times (3.4 ± 3.4% faster; ES = 0.27, p < 0.01), but only a trivial improvement in 50-m backstroke times (1.0 ± 3.1% faster; ES = 0.07, p = 0.19). Females had substantially greater improvements than males in both 50-m (2.4 ± 2.7% faster vs. -0.2 ± 3.2% slower) and 100-m (5.1 ± 2.6% faster vs. 2.0 ± 3.5% faster) backstroke time trials, but with the small sample size, this warrants further investigation. Conclusions. We demonstrated that adding a 3-week combined in-water resisted and assisted training was likely more beneficial for the longer 100-m distance; females seemed to benefit more than males. [ABSTRACT FROM AUTHOR]

Aim of the current study was to examine the reliability and validity of a new tool, developed for the assessment of young swimmers' technique in all swimming strokes. The sample of the study was 119 swimmers (63 boys and 56 girls), aged 8 to 12 years old. To evaluate swimmers' technique, each of them performed 15m for each one of the swimming strokes in individual medley order. ? digital camera, placed 5m above the pool's surface, recorded the swimming bouts. Three experienced swimming coaches evaluated the recorded videos with the new technique's evaluation tool named Tec Pa. Tec Pa assess six important key points of swimming technique in each stroke. According to the results no statistical significant differences were showed between the scores of the swimmers' evaluation by the three coaches (p > 0.05). Moreover, the association between the scores was statistically significant high (t = 0.863; p < 0.05). The findings of the current study reveal that Tec Pa is valid and reliable for the young swimmers' technique evaluation, with high strength of association. Also, Tec Pa can be used by the coaches to enhance the free observation method, which is mainly used, in young swimmers. [ABSTRACT FROM AUTHOR]

The current study investigated body roll amplitude and timing of its peak in backstroke and compared them with front crawl swimming. Nineteen anatomical landmarks were digitised using 80 swimming trial videos (ten swimmers × two techniques × four intensities) recorded by two above- and four below-water cameras. One upper-limb cycle was analysed for each trial, and shoulder and hip roll, whole-body roll (WBR), and WBR due to the buoyant torque (WBRBT) were obtained. Main effects of intensity and technique on the amplitude and timing to reach the peak in those variables were assessed by two-way repeated-measures ANOVA. Swimmers decreased their WBRBT amplitude with an increase in the intensity in both techniques (p ≤ 0.005). The same result was observed for the amplitude of WBR, shoulder roll, and hip roll only in front crawl (p ≤ 0.017). Swimmers maintained the timing of peak WBRBT in both techniques, while they shifted the timing of WBR and hip roll peak toward the beginning of the cycle when increasing the intensity in front crawl (p ≤ 0.017). In conclusion, swimmers maintain the amplitude of WBR, shoulder roll, and hip roll in backstroke when the intensity increases, whereas they reduce the amplitude of all rolls in front crawl. [ABSTRACT FROM AUTHOR]

A good swimming start was contributed to the encouragement that swimmers can used this. The start contributed 10% from the amount of time on a swimming competition with distance 50 meters. The study purpose was analyzed the backstroke movement of Indonesian swimming athletes in the 14-year age group including the distance of jumps, impulses, travel time in the air, the take off angle, the angle of knee at the start block, and angle of fall. Type of qualitative research with a descriptive analysis approach. The sample are 3 swimming athletes. Data was taken by recording the backstroke swimming start movement and then analyzed with dartfish software and looking for the amount of impulse produced. Motion analysis shown that the backstroke start technique performed by swimmer 3 is better than swimmer 1 and swimmer 2 because it results longer jump distances, greater impulses and shorter air travel time. The starting technique was performed with the knee angle at the start block at 34°, the take off angle at 22°, the falling angle at 38° resulting jump distance of 255.90 cm, an impulse of 2.5057 Ns, and a travel time in air 48 seconds. [ABSTRACT FROM AUTHOR]

The article investigates the influence of head depth, speed, and distance associated to safety in backstroke starts. It examines whether these variables are a function of age or not. It finds out that older swimmers are more vulnerable to injury when performing backstroke starts in shallow water than their younger counterparts. It concludes that backstroke start's maximum head depth is not different than the other competitive strokes among the older swimmers.

Objective. The purpose of the paper is to highlight the kinematic and dynamic characteristics of sports technique key elements of the start in backstroke swimming style in the students of higher education of other profiles. Methods. This scientific undertaking entailed the organization of an ascertaining experimental study, using the following research methods: bibliographic review of the specialized literature; video computerized literature, by means of Pinnacle Studio, Kinovea and Physics ToolKit programs; method of movement postural orientation for the analysis of sports technique; statistical-mathematical method using KyPlot program and the method of graphical representation of the results. The research was carried out throughout the period October 2017 - January 2018 and involved 12 students of second year, series 2 from the Faculty of General Medicine. The physical training level of the subjects of the study was evaluated with the help of the test events included in the university curriculum of the higher education of other profiles within the „Carol Davila" University of Medicine and Pharmacy of Bucharest. Results. The study results point out the development level of arms, abdomen and legs muscle strength in the students under study. The use of the video computerized method revealed and identified the kinematic and dynamic characteristics of sports technique key elements of the start in backstroke swimming style in terms of initial posture, launching posture, multiplication of body posture (flight through the air) and concluding posture (entering the water). The work under water and the emerging out of the water prove the accuracy of the execution. The angular characteristics of the positions of sports technique key elements, the trajectory of GCG, the linear and angular velocity of body segments and the resultant of force were highlighted within the phasic structure. Conclusions. The video computerized analysis method used in accordance with the method of movement postural orientation showed the kinematic and dynamic characteristics of the sports technique key elements and enabled. a more thorough knowledge of the phasic structure of the start in backstroke swimming style in the students of higher education of other profiles. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to determine kinematic and energetic differences between front crawl and backstroke performed at the same aerobic speeds.Methods: Ten male competitive swimmers performed front crawl and backstroke at a pre-determined sub-anaerobic threshold speed to assess energy cost (through oxygen uptake measurement) and kinematics (using three-dimensional videography to determine stroke frequency and length, intra-cycle velocity fluctuation, three-dimensional wrist and ankle speeds, and vertical and lateral ankle range of motion). For detailed kinematic analysis, resultant displacement, the duration, and three-dimensional speed of the wrist during the entry, pull, push, and release phases were also investigated.Results: There were no differences in stroke frequency/length and intra-cycle velocity fluctuation between the swimming techniques, however, swimmers had lower energy cost in front crawl than in backstroke (0.77 ± 0.08 vs 0.91 ± 0.12 kJ m-1, p < 0.01). Slower three-dimensional wrist and ankle speeds under the water (1.29 ± 0.10 vs 1.55 ± 0.10 and 0.80 ± 0.16 vs 0.97 ± 0.13 m s-1, both p < 0.01) and smaller ankle vertical range of motion (0.36 ± 0.06 vs 0.47 ± 0.07 m, p < 0.01) in front crawl than in backstroke were also observed, which indirectly suggested higher propulsive efficiency in front crawl.Conclusion: Front crawl is less costly than backstroke, and limbs motion in front crawl is more effective than in backstroke. [ABSTRACT FROM AUTHOR]

Our aim was to compare non-linear and linear mathematical model responses for backstroke start performance prediction. Ten swimmers randomly completed eight 15 m backstroke starts with feet over the wedge, four with hands on the highest horizontal and four on the vertical handgrip. Swimmers were videotaped using a dual media camera setup, with the starts being performed over an instrumented block with four force plates. Artificial neural networks were applied to predict 5 m start time using kinematic and kinetic variables and to determine the accuracy of the mean absolute percentage error. Artificial neural networks predicted start time more robustly than the linear model with respect to changing training to the validation dataset for the vertical handgrip (3.95 ± 1.67 vs. 5.92 ± 3.27%). Artificial neural networks obtained a smaller mean absolute percentage error than the linear model in the horizontal (0.43 ± 0.19 vs. 0.98 ± 0.19%) and vertical handgrip (0.45 ± 0.19 vs. 1.38 ± 0.30%) using all input data. The best artificial neural network validation revealed a smaller mean absolute error than the linear model for the horizontal (0.007 vs. 0.04 s) and vertical handgrip (0.01 vs. 0.03 s). Artificial neural networks should be used for backstroke 5 m start time prediction due to the quite small differences among the elite level performances. [ABSTRACT FROM AUTHOR]

Swimming tests are used in every training cycle and seasons with purpose of estimating swimming performance and evaluate certain training types. The focus of this study is an attempt to distinguish between the potential short-distance and longer-distance swimmers, as well as the swimmers who could have desirable profiles for particular swimming styles. For this purpose, several aims are given: 1) to determine the latent dimensions of the performances in swimming tests, conducted on various distances and performed using different swimming styles; 2) to determine the correlations between speeds on various distances using different swimming styles; 3) to determine the differences in various distance speeds at the same swimmers ; 4) to determine the profiles of swimmers, based on the various distance speeds (4). Male swimmers (N=68), aged 14 to 16 from five Zagreb clubs were tested. Four swimming tests were used to measure speed (25-m freestyle, backstroke, breaststroke, butterfly), five swimming tests measured speed endurance (50-m freestyle, 100-m freestyle, backstroke, breaststroke, butterfly), while only one test measured endurance (800-m freestyle). The results revealed two interpretable and highly reliable latent dimensions of swimming tests. Factor analysis of the scores in swimming tests differentiated the variables of swimming tests that describe breaststrokes and other strokes. Most of the scores in the swimming tests are positively correlated (in range 0.25-0.85), while no differences in various distance speeds among the same swimmers are found. The results indicate the importance of using swimming tests, especially in breaststrokes styles, because of their specific motor structure. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the association between race-start wall contact time and final performance for each sex as a function of classification and anti-slip start-device use (with or without) in backstroke events of international competitions. Twenty-one international competitions covering a 10-year period (2006–2015) were analysed, retrospectively. The data corresponded to the competition histories of 1723 swimmers. For the contact-time data of each event (50-m, 100-m and 200-m), two-way ANOVAs (sex × classification and sex × start device use) were performed. The Bonferroni post-hoc test was used to compare means, and Pearson’s simple correlation coefficient to determine possible correlations between wall contact times and final performance. The results showed the men to have shorter wall contact times than the women in the 50-m and 100-m events, and that, for the women medallists, their wall contact times were positively correlated with final performance in all events except the 200-m swim without the start device. [ABSTRACT FROM PUBLISHER]

Purpose: The biomechanical adaptations in front crawl and backstroke swimming, as influenced by the implementation of a concurrent teaching programme were analysed. Methods: Sixteen participants (19.75 ± 1.13 years) underwent a 30 weeks intervention characterized by an increasing complexity to accomplish motor skills in the following order: (i) lower limbs propulsion; (ii) lower limbs propulsion synchronized with breathing cycle; (iii) lower limbs propulsion synchronized with one upper limb action; (iv) lower limbs propulsion synchronized with both breathing cycle and one upper limb action; (v) full swimming stroke; (vi) motor trajectory of the arms stroke. Performance and biomechanics were measured at front crawl and backstroke during three time points throughout the programme. Results: There were improvements in performance over time at front crawl (21.49 s to 19.99 s, p < 0.01) and backstroke (27.15 s to 24.60 s, p = 0.01). Significant improvements were found for velocity at front crawl (1.13 m/s to 1.22 m/s, p < 0.01) and backstroke (0.92 m/s to 1.00 m/s, p < 0.01). Stroke frequency increased at backstroke (0.64 to 0.73 Hz, p = 0.01), while the intra-cyclic variation of the velocity decreased at front crawl (0.13 to 0.12%, p = 0.02). There was also a moderate-high inter-subject variability in response to the programme. Conclusions: These findings prove that a programme of 30 weeks teaching concurrently front crawl and backstroke is effective to promote similar biomechanical adaptations in low-tier swimmers. However, each subject shows an individual response to better adapt the biomechanical actions and to reach a higher level of expertise. [ABSTRACT FROM AUTHOR]

Copyright of International Journal of Medicine & Science of Physical Activity & Sport / Revista Internacional de Medicina y Ciencias de la Actividad Física y del Deporte is the property of Revista Internacional de Medicina y Ciencias de la Actividad Fisica y del Deporte and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The aim of this study was to compare the non-linear properties of the four competitive swim strokes. Sixty-eight swimmers performed a set of maximal 4 × 25m using the four competitive swim strokes. The hip’s speed-data as a function of time was collected with a speedo-meter. The speed fluctuation (dv), approximate entropy (ApEn) and the fractal dimension by Higuchi’s method (D) were computed. Swimming data exhibited non-linear properties that were different among the four strokes (14.048 ≤ dv ≤ 39.722; 0.682 ≤ ApEn ≤ 1.025; 1.823 ≤ D ≤ 1.919). The ApEn showed the lowest value for front-crawl, followed by breaststroke, butterfly, and backstroke (P < 0.001). Fractal dimension and dv had the lowest values for front-crawl and backstroke, followed by butterfly and breaststroke (P < 0.001). It can be concluded that swimming data exhibits non-linear properties, which are different among the four competitive swimming strokes. [ABSTRACT FROM AUTHOR]

How do speakers know when they can use language creatively and when they cannot? Prior research indicates that higher frequency verbs are more resistant to overgeneralization than lower frequency verbs with similar meaning and argument structure constraints. This result has been interpreted as evidence for conservatism via entrenchment, which proposes that people prefer to use verbs in ways they have heard before, with the strength of dispreference for novel uses increasing with overall verb frequency. This paper investigates whether verb frequency is actually always relevant in judging the acceptability of novel sentences or whether it only matters when there is a readily available alternative way to express the intended message with the chosen verb, as is predicted by statistical preemption. Two experiments are reported in which participants rated novel uses of high and low frequency verbs in argument structure constructions in which those verbs do not normally appear. Separate norming studies were used to divide the sentences into those with and without an agreed-upon preferred alternative phrasing which would compete with the novel use for acceptability. Experiment 2 controls for construction type: all target stimuli are instances of the caused-motion construction. In both experiments, we replicate the stronger dispreference for a novel use with a high frequency verb relative to its lower frequency counterpart, but only for those sentences for which there exists a competing alternative phrasing. When there is no consensus about a preferred way to phrase a sentence, verb frequency is not a predictive factor in sentences' ratings. We interpret this to mean that while speakers prefer familiar formulations to novel ones, they are willing to extend verbs creatively if there is no readily available alternative way to express the intended meaning. [ABSTRACT FROM AUTHOR]

The aim of this paper is to determine any difference between a traditional two semesters continued teaching and a ten-day course block scheduling. The sample comprised the third-year students of the Faculty of Sport and Physical Education in Leposavic, attendeding the Swimming and Water polo courses. The sample consisted of 142 students, 74 of whom regularly attended class, while 68 of them attended a ten-day course covering the same material. To evaluate the acquisition of the necessary skills, following was used: 200 m freestyle time and the evaluation of the butterfly performance, breaststroke and backstroke technique at a distance of 25 m. The results were obtained by applying a t-test for independent samples, and the Mann- Whitney U test. Based on the obtained results it could be concluded that the swimming curriculum realized over a ten-day course gave better result for the training of the swimming technique of the Faculty of Sport and Physical Education students in Leposavi which questions the validity of the current realization of the swimming course in most faculties of this kind. [ABSTRACT FROM AUTHOR]

The aim of the study was to determine which of the motoric and anthropometric variables dominant on 50 meter four competitive swimming styles. The study consisted of 20 girls (M age = 16.50 ± 0.51 years) and 20 boys (M age = 16.50 ± 0.51 years), for a total of 40 swimmers volunteer individuals. Motoric performance tests, anthropometric measurements and body composition assessment were performed for all participants. The 50-meter swimming performance was determined in peak official competition. Simple Linear Regression analysis was used to determine the dominant variables in each of the swimming styles. As a result of simple linear regression, standing horizontal jump, and aerobic endurance were dominant parameters in boys for four swimming styles (P < 0.001). Standing horizontal jump, and aerobic endurance, sit and reach flexibility, agility, and balance were significantly prominent predictive variables in girls for four swimming styles (P < 0.001). Body height, hand and foot lengths were seen as dominant variables for the breaststroke, backstroke swimming styles in girl swimmers (P < 0.001). The findings suggested that standing horizontal jump, and aerobic endurance are dominant predictive parameters in 50-meter swimming performance for four swimming styles in both genders. Besides, body height, hand, and foot lengths could appear as predictive variables for the breaststroke, backstroke swimming styles in girl swimmers. [ABSTRACT FROM AUTHOR]

As sprint swimming events can be decided by margins as small as .01 s, thus, an effective start is essential. This study reviews and discusses the 'state of the art' literature regarding backstroke start biomechanics from 23 documents. These included two swimming specific publications, eight peer-reviewed journal articles, three from the Biomechanics and Medicine in Swimming Congress series, eight from the International Society of Biomechanics in Sports Conference Proceedings, one from a Biomechanics Congress and one academic (PhD) thesis. The studies had diverse aims, including swimmers' proficiency levels and data collection settings. There was no single consensus for defining phase descriptions; and kinematics, kinetics and EMG approaches were implemented in laboratory settings. However, researchers face great challenges in improving methods of quantifying valid, reliable and accurate data between laboratory and competition conditions. For example, starting time was defined from the starting signal to distances as disparate as ~5 m to 22.86 m in several studies. Due to recent rule changes, some of the research outcomes now refer to obsolete backstroke start techniques, and only a few studies considered the actual international rules. This literature review indicated that further research is required, in both laboratory and competition settings focusing on the combined influences of the current rules and block configuration on backstroke starting performances [ABSTRACT FROM AUTHOR]

Swimming results are permanently improving. Results in individual medley disciplines are also improving. Individual medley disciplines are consist of all four swimming techniques. Results in these disciplines depends among other things, on the swimming quality in all techniques. In 200m individual medley, each technique implies 50m swimming, in following order: butterfly, backstroke, breast stroke and free style. The aim of this paper is to determine individual affect of each swimming technique on 200m individual medley final result. Research was based on the achieved times of 30 male and 30 female swimmers who participated in 200m individual medley qualifications on European championship - Szczecin 2011, Poland. According to adequate statistical methods and analysis of results, certain conclusions will be derived. [ABSTRACT FROM AUTHOR]

The article discusses a study on pain prevalence in swimming athletes of São Caetano do Sul, Brazil. The researchers conducted a survey on 71 athletes and the results were analyzed by Two-Proportional Equality Test and Mann-Whitney Test. The results show that there was high prevalence not presenting correlation with the backstroke style.

The purpose of the present study was to investigate different biomechanical variables of backstroke technique in swimmers specialized in different distance events, in order to investigate the capacity to modify the timing of the arm stroke when changing the swimming velocity from sub-maximal to maximal. Two 25-m backstroke trials respectively at 70% of maximum velocity (V70) and at 100% of maximum velocity (Vmax) were performed by 9 200-m distance swimmers and 9 50-m distance swimmers. Swimming velocity, stroke length, stroke rate, duration of different phases of the arm stroke and selected kinematic variables were assessed in both cases. In the 50-m distance swimmers, the duration of the propulsive phase at Vmax, expressed as a percentage of the duration of the total underwater arm stroke, increased significantly (p = 0.001) with increasing swimming velocity. Specifically, both the pull and push phases were fundamental in the increase of duration of the propulsive phase. When compared to 200-m specialists, 50-m distance swimmers seem to be more able to modify their arm stroke phases duration when increasing the swimming velocity in backstroke. [ABSTRACT FROM AUTHOR]

A computational fluid dynamics (CFD) based analysis of the propulsive forces generated by two distinct styles of arm-pulls in front-crawl as well as backstroke is presented in this Technical Brief. Realistic models of the arm pulling through water are created by combining underwater video footage and laser-scans of an arm with computer animation. The contributions of drag and lift forces on the arm to thrust are computed from CFD, and it is found that lift forces provide a dominant contribution to thrust for all the arm-pull styles examined. However, contrary to accepted notions in swimming, pronounced sculling (lateral motion) not only does not increase the contribution of lift forces on the hand to overall thrust, it decreases the contribution of drag forces to thrust. Consequently, pronounced sculling seems to reduce the effectiveness of the arm-pull. [ABSTRACT FROM AUTHOR]

Collective tactics is based on division of the roles in all phases of the game. Positions, either role in the water polo, are instrumentality in realization of collective tactics. Roles in water polo are: center forward, guard, wing, external attacker and goal keeper. The aim in this study was to describe the role of the Guard (G) and to compare it with other roles. The subject of this investigation is description of all activities in the game without contact with the ball (all swimming, duels, play with player more or less). Data collection was performed by registration of player's activity during official games of the International Adriatic Water Polo League in the season 2009/10. Main units of measuring, entities, were positionplayer- quarter. The results were reiterated by 21 indicators and main statistics was compiled. Differential analysis for position G with respect to other players (positions) was performed on the basis of testing the model of binary logistic regression equitation. This proportion is evaluated on the basis of frequencies of backstroke swimming at maximum intensities (0.2:0-1) and frequencies swam by crawl technique at maximum intensity (2.9:2.3) as well as frequencies of breaststroke swimming at light intensity (1.45:1.0). In total distance swam G is statistically equal with other players. Statistically significant hi is different from other players in meters swam at maximum intensity (32.1:21.6) where there is a statistically significantly contribution of meters swam in crawl technique at maximum intensity (31.4:21.3). In the play with unequal number of players (player more/less) there are no significant differences regarding the players in other roles in the game. There is a statistically significant and remarkable difference of G from other players both in frequencies (3.1:2.6) and in the time (21.8:14.1) spent in duels. By application of binary logistic regression we defined differential characteristics of G regarding other roles in the game and that typified in equitation of play structure on the position G. Solitary contributions in prediction of role G are represented in linear equitation for position G. Results of this investigation will contribute in elaboration of water polo game model in the domain of situational play without ball (realization of the collective tactics regardless the choice of the type of tactics in either attack or defense). The result brings statistical descriptions of the role G as well as, in an unusual analysis, it brings comparative properties of the role G in relation to others. [ABSTRACT FROM AUTHOR]

In this article, we present a critical review of the swimming literature on body roll, for the purposes of summarizing and highlighting existing knowledge, identifying the gaps and limitations, and stimulating further research. The main research findings can be summarized as follows: swimmers roll their shoulders significantly more than their hips; swimmers increase hip roll but maintain shoulder roll when fatigued; faster swimmers roll their shoulders less than slower swimmers during a 200-m swim; roll asymmetries, temporal differences in shoulder roll and hip roll, and shoulder roll side dominance exist in front crawl swimming, but there is no evidence to suggest that they affect swimming performance; and buoyancy contributes strongly to generating body roll in front crawl swimming. Based on and stimulated by current knowledge, future research should focus on the following areas: calculation of body roll for female swimmers and for backstroke swimming; differences in body roll between breathing and non-breathing cycles; causes of body roll asymmetries and their relation to motor laterality; body roll analysis across a wide range of velocities and swimming distances; exploration of the association between body roll and the magnitude and direction of propulsive/resistive forces developed during the stroke cycle; and the influence of kicking actions on the generation of body roll. [ABSTRACT FROM AUTHOR]

Underwater undulatory swimming (UUS) is often perceived to be a nonessential aspect of aquatic propulsion. Given their solid theoretical and practical training in swimming, physical education students should be capable of judging the true value of the "fifth stroke," since it appears to be the most efficient technique in high level, competitive swimming. To compare opinions and connotations associated with the stroke and the four official strokes (butterfly, backstroke, breaststroke, and crawl), 198 students (32 of whom were expert swimmers; M age=20.6 yr., SD= 1.2), were surveyed using the semantic differential of Osgood, Suci, and Tannenbaum. Al- though answers of expert and nonexpert swimmers differed significantly (p <.01, except for the breaststroke), participants considered overall that undulatory stroke was less attractive, less powerful, and less rapid than the four surface strokes (d=2.88 for the expert swimmers). Putting one arm in front of the other and repeating the sequence still remains the most solidly held representation of "the right way" to swim. However, the high observed standard deviations for the underwater undulatory stimulus (SD ≥ 1.1 with SD max =3 for the expert swimmers) attests to the view being less strongly held by swimming specialists. [ABSTRACT FROM AUTHOR]

In this study, we assessed arm coordination in the backstroke over increasing speeds by adapting the index of coordination originally used in the front crawl. Fourteen elite male backstroke swimmers swam four trials of 25 m at the speeds corresponding to the 400-m, 200-m, 100-m, and 50-m events. The six phases of the arm stroke were identified by video analysis and then used to calculate the index of coordination, which corresponded to the time between the propulsive phases of the two arms. With increases in speed, the elite swimmers increased the stroke rate, the relative duration of their arm pull, and their index of coordination, and decreased the distance per stroke (P < 0.05). Arm coordination was always in catch-up (index of coordination of -12.9%) because the alternating body-roll and the small shoulder flexibility did not allow the opposition or superposition coordination seen in the front crawl. This new method also quantified the relative duration of the hand's lag time at the thigh, which did not change (∼2%) with increasing speed for the elite swimmers. The index of coordination enables coaches to assess mistakes in backstroke coordination, particularly in the hand's lag time at the thigh. [ABSTRACT FROM AUTHOR]

Introduction: Physical activities in water environment are essential for man's health. The level of swimming abilities is conditioned by level of swimming technique. Improving of swimming technique is not time conditioned and therefore it makes a very important part of swimming lessons. Our paper brings knowledge about the differentiated efficiency of on physical load while improving swimming technique of adults. The aim of the paper was to find out intensity of load during adult's swimming lessons. We wanted to adapt the content of the lessons to improve swimming technique. Materials and Methods: We monitored two women (34 years and 35 years) and one man (44 years) during a swimming course for adults (20 lessons), twice a week. All monitored adults were on the same swimming level, they were able to swim 50m breaststroke and backstroke. We used the Carvonen Formula for specifying the aerobic zone. Minimum was counted with 60% HRmax (or 50%) and maximum with 80% HRmax (or 70%). Results: The following factors influenced the proportionality of load during the lessons: previous water experience (psychic blocks), somatic predispositions, quality of swimming skills, age. The highest heart rate was measured during lessons of improving crawl and backstroke technique. Discussion: The swimming lessons of adults can be placed among the physical activities in water environment which develop physical condition and have mostly aerobic character. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess stroke rate variability in elite female swimmers (200-m events, all four techniques) by comparing the semi-finalists at the Athens 2004 Olympic Games (n = 64) and semi-finalists at the French National 2004 Championship (n = 64). Since swimming speed (V) is the product of stroke rate (SR) and stroke length (SL), these three variables and the coefficient of variation of stroke rate (CVSR) of the first and second 100 m were determined (V1, V2; SR1, SR2; SL1, SL2; CVSR1, CVSR2) and differences between the two parts of the events were calculated (ΔV; ΔSR; ΔSL; ΔCVSR). When the results for the four 200-m events were analysed together, SR1, SR2, SL1, and SL2 were higher (α = 0.05, P < 0.001) and ΔV, ΔSR, and ΔCVSR were lower (P < 0.01) in the Olympic group than in the National group. The Olympic-standard swimmers exhibited faster backstrokes and longer freestyle strokes (P < 0.05). Both CVSR1 and CVSR2 were lower for freestyle and backstroke races in the Olympic group than in the National group (P < 0.001). Our results suggest that stroke rate variability is dependent on an interaction between the biomechanical requisites of the task (techniques) and the standard of the swimmer. [ABSTRACT FROM AUTHOR]

There is an obvious lack of studies examining the ability grouping effects in kinesiology. Therefore, the aim was to establish the probable differential effects of the heterogeneous (control - C) vs. ability grouping (experimental - E) programmes in a higher education swimming curriculum. In this experiment male students (21 ± 0.9 years) were the sample of subjects. The E group participated in a swimming-course divided into three swimming ability-based subgroups, whereas the C group participated in a swimming programme, randomly divided into three heterogeneous subgroups. Apart from the quantitative changes, the qualitative changes were also studied. An analysis of variance showed significant improvement in the six measured swimming variables (25, 50 and 300 metres front crawl stroke; 50 metres butterfly stroke and backstroke; 100 metres breaststroke) in both groups. In conclusion, (a) the factor analysis computed on the variables of the differences, and (b) the canonical discriminant analysis calculated in the initial and final measurements marked the B programme as: (a) qualitatively, and (b) quantitatively superior when compared to the C programme. [ABSTRACT FROM AUTHOR]

Kinetic (3-D force plate), kinematic (videography) and temporal characteristics of backstroke turns by 20 male and 16 female swimmers were recorded to identify and describe key elements of backstroke turning performance. Data were recorded during a 50m maximum effort swim in a 25 metre pool. A Pearson product moment correlation matrix revealed that the 5 m RTT' was significantly correlated with anthropometric measures of height, mass, trochanteric height and age; kinetic measures of horizontal impulse and peak force; and kinematic measures of wall contact time and peak velocity. The stepwise multiple regression equation to predict 5 m RTT was: 19.6-0.75 trochanteric height-1.8 wall exit velocity-0.03 peak vertical force. Four key factors were identified from a principle components factor analysis - anthropometry and force, post-turn velocity, force preparation and rotational skills. Implications from the findings were that age-group backstrokers should `hit the wall hard' with relatively extended legs to reduce swim distance and push-off deceleration; use minimal wall contact time, and maximise forces to develop high horizontal velocities in a streamlined position. [ABSTRACT FROM AUTHOR]

Analyzes the effects of skill on swimmers' performance of the backstroke. Stroke rate and length; Correlation coefficients; Coordination index.

Discusses upper extremity and trunk stabilization exercises for swimmers. Propulsion and recovery phase exhibited by the freestyle, backstroke, breaststroke and butterfly stroke; Importance of maintaining the ability to establish proper core positioning and stability while functionally strengthening the upper extremity; Mechanism for establishing dry-land stabilization exercises for the both the shoulder and the trunk.