This article was downloaded by: [b-on: Biblioteca do conhecimento online UP] On: 13 March 2012, At: 04:19 Publisher: Routledge Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK Journal of Sports Sciences Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/rjsp20 Kinematic analysis of three water polo front crawl styles Karla De Jesus a, Pedro Figueiredo a, Kelly De Jesus a, Filipa Pereira a, J. Paulo Vilas-Boas a, Leandro Machado a & Ricardo J. Fernandes a a Centre of Research, Education, Innovation and Intervention in Sport, Faculty of Sport, University of Porto, Porto, Portugal Available online: 12 Mar 2012 To cite this article: Karla De Jesus, Pedro Figueiredo, Kelly De Jesus, Filipa Pereira, J. Paulo Vilas-Boas, Leandro Machado & Ricardo J. Fernandes (2012): Kinematic analysis of three water polo front crawl styles, Journal of Sports Sciences, DOI:10.1080/02640414.2012.669043 To link to this article: http://dx.doi.org/10.1080/02640414.2012.669043 PLEASE SCROLL DOWN FOR ARTICLE Full terms and conditions of use: http://www.tandfonline.com/page/terms-and-conditions This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.
Journal of Sports Sciences, 2012; 1 9, ifirst article Kinematic analysis of three water polo front crawl styles KARLA DE JESUS, PEDRO FIGUEIREDO, KELLY DE JESUS, FILIPA PEREIRA, J. PAULO VILAS-BOAS, LEANDRO MACHADO, & RICARDO J. FERNANDES Centre of Research, Education, Innovation and Intervention in Sport, Faculty of Sport, University of Porto, Porto, Portugal (Accepted 20 February 2012) Downloaded by [b-on: Biblioteca do conhecimento online UP] at 04:19 13 March 2012 Abstract During water polo matches, players use different front crawl styles. The purpose of this study was to conduct a kinematic analysis of three water polo front crawl styles: front crawl with head under water, front crawl with head above water, and front crawl when leading the ball. Ten proficient water polo players performed 3 6 15 m sprints in each front crawl style, which were recorded three-dimensionally by two surface and four underwater cameras. The results showed no differences in performance and several kinematic characteristics among the water polo front crawl styles. However, front crawl when leading the ball showed shorter stroke length and greater stroke frequency. Front crawl with head underwater presented greater maximal finger depth and elbow angle at mid-stroke position. Front crawl with head above water and when leading the ball showed greater trunk obliquity and maximal depth of right and left foot, and shorter kick stroke frequency. The findings suggest that proficient players learn to master front crawl with head above water to achieve top velocity. Despite the common use of the front crawl with head underwater as the basis for water polo fast displacement, coaches should emphasize the use of the specific water polo styles to attain high performance. Keywords: Biomechanics, front crawl, performance, three-dimensional analysis, water polo Introduction Water polo is a high-intensity sport in which players swim, jump, pass the ball, and struggle against their opponents using blockades, beatings, contacts, and pushes (Escalante, Saavedra, Mansilla, & Tella, 2011; Smith, 1998). Swimming movements are performed to gain an advantage over an opponent, or to defend against attacking manoeuvres (Smith, 1998). Water polo players often alternate between vertical and horizontal swimming (Lupo et al., 2009), the latter being performed between approximately 45% and 55% of the overall playing time (Lupo et al., 2009; Smith, 1998). In 2005, the Fédération Internationale de Natation (FINA) changed the water polo rules to make the game faster (Platonou & Geladas, 2006) and more offensive (Platonou, 2009), increasing game duration and decreasing ball possession time; this modification enhanced the importance of swimming for locomotion purposes (Lupo et al., 2009; Platonou & Varamenti, 2011; Tan, Polglaze, & Dawson, 2009). Although water polo is played above the water surface, implying that players often assume the vertical position, front crawl swimming is a frequently used technique (Platonou & Geladas, 2006). Dopsaj and colleagues (Dopsaj, Madic, & Okicic, 2007) and Tan et al. (2009) observed that water polo players covered about 700 1350 m throughout a game, of which *90% is carried out using the front crawl technique, *28% (280 430 m) is performed at maximum (or near maximum) intensity, and players lead the ball in *7% of situations. Lupo et al. (2009) also reported that players performed fewer swimming patterns with than without the ball, representing *96% of up to 10 s of horizontal swimming. Unlike swimming events, during a water polo game players use the front crawl technique for different purposes and use different styles: front crawl with head under water, front crawl with head above water, and front crawl when leading the ball (Dopsaj et al., 2007). Clarys and colleagues (Clarys, Jiskoot, & Lewillie, 1976) were the first to compare the front crawl technique and the water polo style performed with head above water, and observed strong photogrammetric and electromyographic similarities, but also some differences in the respective body positions. More recently, Zamparo and Correspondence: R. J. Fernandes, Centre of Research, Education, Innovation and Intervention in Sport, Faculty of Sport, University of Porto, Rua Dr. Plácido Costa 91, 4200 Porto, Portugal. E-mail: ricfer@fade.up.pt ISSN 0264-0414 print/issn 1466-447X online Ó 2012 Taylor & Francis http://dx.doi.org/10.1080/02640414.2012.669043
Downloaded by [b-on: Biblioteca do conhecimento online UP] at 04:19 13 March 2012 2 K. de Jesus et al. Falco (2010) revealed that front crawl with head under water shows kinematic differences (e.g. shorter trunk obliquity) from front crawl with head above water. Using a chronometric method, Dopsaj et al. (2007) pointed out that the differences between the water polo front crawl styles decrease in line with increases in participants playing standard, which indicates that it is highly dependent on training specificity. The above studies, however, have significant limitations owing to the use of methodologies that did not provide a detailed quantitative technical description, such as those frequently used to characterize the conventional front crawl swimming technique, including segmental (e.g. Deschodt, Arsac, & Rouard, 1999) and centre-of-mass kinematic profiles (e.g. McCabe, Psycharakis, & Sanders, 2011). Indeed, according to Platonou and Nikolopoulos (2003), scientifically gathered quantifiable information is needed to design effective water polo training and to establish a valid programme for monitoring players progress. It has been suggested that the exercises used by water polo coaches in their training programmes continue to focus on conventional swimming techniques; however, water polo players do not always propel themselves in an optimized hydrodynamic position, as swimmers do (Gatta, Fantozzi, Cortesi, Patti, & Bonifazi, 2010). Moreover, since stronger, faster, and highly technically developed water polo players is a daily concern of coaches (Escalante et al., 2011; Ferragut et al., 2011), there is a need to identify those kinematic characteristics relevant to explosive power in the water (Platonou, 2005). As a detailed understanding of the kinematics of the different water polo front crawl styles may provide important information for coaches to define more clearly the objectives of training programmes, the aim of this study was to conduct a kinematic analysis and comparison of the three water polo front crawl styles: front crawl with head under water, front crawl with head above water, and front crawl when leading the ball. Given the specialization process and the increased proficiency of highly trained water polo players, it was hypothesized that few kinematic differences would be observed among the three water polo front crawl styles. protocol received approval from the local ethics committee. Test procedure Participants performed a protocol of 3 6 15 m maximum bouts (with 2 min rest between bouts), each using one of the water polo front crawl techniques studied in randomized order: front crawl with head under water, front crawl with head above water (head free to move laterally), and front crawl when leading the ball (Figure 1, panels A, B, and C, respectively). All bouts started in the water, and all swimming was performed in a 25 m swimming pool. Prior to the exercise bouts, the participants performed an individualized low-intensity standard warm-up. Data collection The kinematics of the water polo players were studied using three dimensional [3D:horizontal (x), vertical (z), and lateral (y)] video recordings using two surface and four underwater stationary cameras (Sony 1 DCR-HC42E, Tokyo, Japan), operating at a sampling frequency of 50 Hz, with an electronic shutter speed of 1/250 s. The underwater cameras were positioned 5.00 and 0.62 m away from the frontal and lateral pool wall, respectively, and the angle between the axes of adjacent underwater cameras varied from 758 to 1108 (cf. Figueiredo, Vilas-Boas, Maia, Gonçalves, & Fernandes, 2009). Methods Participants Ten trained male water polo players (mean+s: age 23.2 + 2.4 years; stature 1.76 + 0.06 m; body mass 76.7 + 8.0 kg; fat mass 12.8 + 4.5%; training units per week 6.4 + 0.5) provided written informed consent to participate in the study. The experimental Figure 1. The three water polo front crawl styles: (A) front crawl performed with head under water; (B) front crawl performed with head above water; (C) front crawl when leading the ball.
Kinematic analysis of three water polo front crawl styles 3 Downloaded by [b-on: Biblioteca do conhecimento online UP] at 04:19 13 March 2012 The two aerial cameras were positioned 2.10 and 1.06 m away from the frontal and lateral pool wall, respectively, positioned on a support 5.87 m high with an angle between lenses of *1008. The water polo players were monitored when passing through a specific pre-calibrated space using a calibration frame with orthogonal axes (3 m 6 2m6 3 m, for x, z, and y directions). To eliminate the effect of breathing on kinematic variables when performing front crawl style with head under water, players were instructed to avoid breathing when passing the calibrated space, and familiarized themselves with this non-breathing condition in their individualized warm-up. Players wore a complete swimming suit, with reflective spherical anatomical markers on the trunk, upper and lower right and left limbs. Synchronization of the images was obtained using a pair of lights (fixed to the calibration volume) visible in the field of each video camera. Data processing The three styles of front crawl were analysed kinematically using one complete stroke cycle (defined as the period between the entry of one hand to the next entry of the same hand). All water polo players utilized a six-beat kick per arm stroke cycle during the three front crawl styles. Using the Ariel Performance Analysis System three-dimensional motion analysis software (Ariel Dynamics, Inc., San Diego, CA, USA), the video images were digitized manually and frame-by-frame marker digitization was performed at a frequency of 50 Hz. The anthropometric biomechanical model used was that of Zatsiorsky and Seluyanov (1983) as adapted by de Leva (1996). Twenty anatomical landmarks were used, including the vertex of the head and ear lobe, and the right and left: acromion, lateral humeral epicondyle, ulnar styloid process, third distal phalanx, prominence of greater femoral trochanter external surface, lateral femoral epicondyle, lateral malleolus, calcaneus, and halux. The independent digitization from the six cameras was reconstructed with the help of the calibration volume. Twelve points of calibration were used, and the image coordinates were transformed to three-dimensional object-space coordinates using the direct linear transformation algorithm (Abdel-Aziz & Karara, 1971). After residual analysis for a wide range of cut-off frequencies, 5 Hz was selected as the optimal frequency for the smoothing of the data using a lowpass digital filter. Root mean square (RMS) reconstruction errors of 12 validation points on the calibration frame, which did not serve as control points, were as follows for the x, y, and z axis, respectively: (i) 2.92 mm, 2.80 mm, and 2.05 mm, representing 0.09%, 0.09%, and 0.14% of the calibrated space for above the water, and (ii) 3.38 mm, 4.69 mm, and 2.93 mm, representing 0.11%, 0.15%, and 0.30 % of the calibrated space for under the water. Data analysis The water polo front crawl arm movements were split into four phases (adapted from Chollet, Charlies, & Chatard, 2000; McCabe et al., 2011), determined from the swimmer s x and z positions of the third distal phalanx and acromion (noting the time corresponding to these displacements): (i) entry and catch, between the first z and x negative coordinates of the third distal phalanx; (ii) pull, from the end of the entry and catch until the midstroke position, determined when the x position of the third distal phalanx and acromion are similar; (iii) push, from the end of the pull until the hand s release from the water, determined by the first z positive coordinate of the third distal phalanx after the underwater trajectory; (iv) recovery, from the end of the push until re-entry into the water of the finger, determined by the z positive coordinate of the third distal phalanx. The linear and angular kinematic variables were defined as following: (i) centre-of-mass average horizontal velocity, calculated by dividing the water polo player s mean centre-of-mass horizontal displacement by the time required to complete one stroke cycle; (ii) stroke frequency, the inverse of the time to complete one stroke cycle; (iii) stroke length, the horizontal displacement of the centre of mass during one stroke cycle; (iv) backward displacement of the finger, calculated as the difference between the most forward and backward horizontal coordinates of the third distal phalanx; (v) slip amplitude of the finger, calculated as the difference between the first negative and positive coordinates of the third distal phalanx at entry and exit, respectively; (vi) maximum finger and elbow depth, defined as the most vertical negative coordinate of the third distal phalanx and lateral humeral epicondyle during underwater trajectory; (vii) maximum finger and elbow width, defined as the maximum lateral coordinate of the third distal phalanx and lateral humeral epicondyle with respect to the water polo player s centre of mass; (viii) finger and elbow width range, calculated as the difference between the maximum and minimum lateral coordinates of the third distal phalanx and lateral humeral epicondyle at the pull phase with respect to the water polo player s centre of mass; (ix) elbow angle at the instant of hand entry, beginning of finger backward movement, mid-stroke position, and end of backward movement, defined by the line connecting the arm to the forearm segments; (x) elbow angle range at the pull and push phases,
Downloaded by [b-on: Biblioteca do conhecimento online UP] at 04:19 13 March 2012 4 K. de Jesus et al. calculated as the difference between the elbow angle at mid-stroke position and beginning of finger backward movement, and end of backward movement and mid-stroke position, respectively; (xi) trunk obliquity, defined as the angle with the horizontal of the segment between the acromion and prominence of the greater femoral trochanter at the mid-stroke position; (xii) maximum foot vertical position, defined as the maximum vertical position of the right and left halux at the stroke cycle; (xiii) right and left vertical foot amplitude, defined as the difference in the vertical coordinate of the halux between the maximum up and down, and between the maximum down and up, positions of the leg kick, respectively; (xiv) kick stroke frequency, determined as the inverse of the time between the first and sixth maximum vertical negative coordinates of the halux; (xv) intra-cycle variation of the horizontal velocity of the centre of mass, calculated as the coefficient of variation of the velocity-to-time curves within a stroke cycle (expressed as a percentage); (xvi) index of coordination, calculated as the time elapsed between the propulsion of the right and left arms, and expressed as a percentage of the duration of the complete arm stroke cycle. The reliability of the digitizing process was calculated from two repeated digitizations of a randomly selected trial. The repeatability coefficient [and 95% agreement limits], as described by Bland and Altman (1986), for all variables were as follows: (i) 0.118 m s 1 [70.109 to 0.120] for x centre-ofmass velocity; (ii) 0.007 m, 0.017 m, and 0.006 m [70.006 to 0.009; 70.016 to 0.018; 70.006 to 0.007] for x, z, and y centre-of-mass displacement, respectively; (iii) 0.0002 m [70.0002 to 0.0002] for x displacement of finger; (iv) 0.125 m [70.111 to 0.139] for z position of elbow; (v) 0.019 m [70.009 to 0.028] for z position of finger; (vi) 25.8618 [722.251 to 29.468] for elbow angle; (vii) 0.01068 [70.010 to 0.011] for trunk obliquity; (viii) 0.003 m [70.003 to 0.004] for y displacement of elbow; (ix) 0.0009 m [70.0006 to 0.001] for y displacement of finger and; (x) 0.004 and 0.002 m [70.004 to 0.005; 70.001 to 0.002] for z position of right and left foot, respectively. Statistical analysis Normality distribution was checked with the Shapiro-Wilk test for all parameters. Kinematic data are reported as mean values and standard deviations (+ s). To compare the three water polo front crawl styles, one-way repeated-measures analysis of variance (ANOVA) was performed, and the assumption of sphericity was tested (Mauchly s test). As this assumption was not violated, no further adjustments of the values were required. Post hoc comparisons were conducted with the pair-wise multiple comparison Bonferroni test. The effect size statistic used was partial eta-squared (Z 2 ), derived from one-way ANOVAs. Partial Z 2 is the ratio of the sum of squares for the group effect to the group sum-ofsquares plus the error sum-of-squares. This statistic is interpreted as a squared correlation coefficient: the estimated percent of variance in the dependent variable that can be accounted by the independent variable. Statistical significance was set at P 0.05. Results Means, standard deviations, and effect sizes are displayed in Table I for the parameters assessed. The three water polo front crawl styles did not differ in average horizontal swimming velocity (F 2,18 ¼ 0.40, P ¼ 0.67), but front crawl when leading the ball displayed greater stroke frequency (F 2,18 ¼ 17.49, P 5 0.01) and shorter stroke length (F 2,18 ¼ 16.09, P 5 0.01) than the other two styles, with a large effect size. Analysing the backward displacement and slip amplitude of the finger, no differences were observed (sagittal views of the horizontal displacement of one water polo player for the three styles are presented in Figure 2D, E, and F). The front crawl with head under water showed greater maximal finger depth than the other two styles (F 2,18 ¼ 12.51, P 5 0.01), with a large effect size (for one participant the result agrees well, see Figure 2A and D). For finger and elbow width and width range, no differences were noted (front views of the lateral finger displacement of one water polo player for the three styles are presented in Figure 2A, B, and C). The front crawl with head under water showed greater elbow angle at the mid-stroke position than the other two styles (F 2,18 ¼ 13.82, P 5 0.01), with a large effect size. The three front crawl styles were not different in relation to the elbow angle at the instant of the finger beginning to move horizontally backward, end of backward movement, and finger reentry. The front crawl with head under water presented a lower value for trunk obliquity (F 2,18 ¼ 8.55, P 5 0.01) and maximal right foot depth (F 2,18 ¼ 11.13, P ¼ 0.01) than the other two styles, both with a large effect size. For maximal left foot depth, front crawl with head under water showed a lower value than front crawl when leading the ball (F 2,18 ¼ 11.13, P ¼ 0.05) and front crawl with head above water (although only for a P-value of 0.10), both with a large effect size. For right and left foot amplitude, no differences were observed, and the effect sizes small. Front crawl with head under water showed shorter kick stroke frequency than the other two styles (F 2,18 ¼ 12.93, P 5 0.001), with a large effect size. The three water polo styles did not differ regarding the index of coordination, as
Kinematic analysis of three water polo front crawl styles 5 Table I. Mean (+ s) values of the segmental and centre-of-mass kinematic parameters for the three water polo front crawl styles and effect size (partial Z 2 ) Variables Front crawl head under water Front crawl head above water Front crawl leading the ball Effect size (partial Z 2 ) Downloaded by [b-on: Biblioteca do conhecimento online UP] at 04:19 13 March 2012 Velocity (m s 1 ) 1.50 + 0.06 1.50 + 0.05 1.48 + 0.08 0.043 Stroke frequency (Hz) 1.02 + 0.03 1.09 + 0.08 1.18 + 0.08 a,b 0.660 Stroke length (m) 1.46 + 0.07 1.37 + 0.14 1.25 + 0.11 a,b 0.641 Backward displacement (m) 0.41 + 0.17 0.57 + 0.20 0.53 + 0.14 0.184 Slip amplitude (m) 70.03 + 0.18 70.04 + 0.23 0.08 + 0.18 0.111 Max. finger depth (m) 0.65 + 0.05 b,c 0.59 + 0.04 0.58 + 0.03 0.675 Max. elbow depth (m) 0.35 + 0.09 0.34 + 0.03 0.32 + 0.02 0.124 Max. finger width (m) 0.43 + 0.12 0.36 + 0.16 0.39 + 0.16 0.115 Max. elbow width (m) 0.40 + 0.11 0.36 + 0.08 0.41 + 0.13 0.191 Finger width range (m) 0.26 + 0.12 0.25 + 0.12 0.24 + 0.09 0.024 Elbow width range (m) 0.23 + 0.07 0.17 + 0.05 0.18 + 0.08 0.261 Elbow angle 1st back (8) 99.82 + 32.38 101.99 + 20.13 120.90 + 36.33 0.147 Elbow angle shoulder (8) 162.08 + 14.83 b,c 140.17 + 23.97 128.56 + 22.53 0.606 Elbow angle end back (8) 81.16 + 23.52 83.54 + 15.24 79.58 + 20.49 0.012 Elbow angle re-entry (8) 121.19 + 10.65 121.01 + 16.81 112.04 + 12.20 0.235 Elbow angle range pull (8) 779.91 + 30.92 756.92 + 28.80 748.98 + 34.49 0.259 Elbow angle range push (8) 39.99 + 16.72 37.76 + 16.90 26.43 + 19.05 0.174 Trunk obliquity (8) 6.50 + 1.53 b,c 12.76 + 1.42 13.20 + 0.87 0.517 Max. right foot depth (m) 0.48 + 0.08 b,c 0.59 + 0.07 0.59 + 0.08 0.553 Max. left foot depth (m) 0.50 + 0.05 b,c 0.56 + 0.10 0.58 + 0.09 0.369 Right vertical foot amplitude (m) 0.44 + 0.03 0.45 + 0.01 0.46 + 0.02 0.080 Left vertical foot amplitude (m) 0.45 + 0.02 0.46 + 0.01 0.45 + 0.02 0.075 Kick stroke frequency (Hz) 1.03 + 0.03 b,c 1.11 + 0.09 1.17 + 0.10 0.590 Index of coordination (%) 5.91 + 2.52 4.42 + 3.64 4.93 + 3.33 0.081 a Significantly different from front crawl with head under water. b Significantly different from front crawl with head above water. c Significantly different from front crawl when leading the ball. denoted by the level of significance and small effect size. For all styles, the IdC values indicated an interarm coordination in superposition mode (i.e. IdC 4 0%). Figure 3 presents the mean curves for all water polo players of the intra-cycle variation in horizontal velocity of the centre of mass during the three water polo front crawl styles. For all styles, the intra-cycle variation of the horizontal velocity of centre of mass did not differ (F 2,18 ¼ 0.49, P 4 0.05, partial Z 2 ¼ 0.05) and was characterized by a low (*15%) and stable profile with few variations. Discussion Although water polo players differ by playing position in their anthropometric characteristics (Ferragut et al., 2011; Smith, 1998) and swimming intensity (Tan et al., 2009), swimming technique needs to be optimized independently of players specialization (Smith, 1998; Tan et al., 2009), to ensure success in elite-standard competition (Escalante et al., 2011). The aim of the present study was to characterize and compare kinematically three water polo front crawl styles: front crawl with head under water, front crawl with head above water, and front crawl when leading the ball (cf. Figure 1). The results indicated that the three water polo front crawl styles differ in some kinematic parameters, and most of these differences were evidenced between the front crawl style performed with head under water and the other two styles, which confirms our hypothesis. Nevertheless, these mechanical changes were ineffective for all three styles, once players showed similar and stable inter-arm coordination and swim efficiency parameters. The few technical modifications could be related to the water polo players specialty, particularly front crawl style performed with head above water, which seems to be stabilized during training. For average centre-of-mass horizontal velocity, the three front crawl styles presented similar values, which is at odds with Clarys et al. (1976) and Zamparo and Falco (2010), who observed that water polo players achieved greater horizontal velocity in front crawl with head under water than front crawl with head above water. Differences may be due to the greater specialization of the sample of the current study. Indeed, Dopsaj et al. (2007) reported that differences between front crawl styles depend on specific training and technical indicators, becoming less marked with increasing competitive standard. Since water polo players perform a series of swimming sprints during a match (Gatta et al., 2010),
Downloaded by [b-on: Biblioteca do conhecimento online UP] at 04:19 13 March 2012 6 K. de Jesus et al. Figure 2. Representative example of horizontal, vertical, and lateral finger displacements for the three water polo front crawl styles. Frontal view of finger displacement for the front crawl performed with head under water (A), front crawl performed with head above water (B), and front crawl when leading the ball (C). Sagittal view of finger displacement for the front crawl performed with head under water (D), front crawl performed with head above water (E), and front crawl when leading the ball (F). The entry and catch (A B), pull (B C), push (C D), and recovery (D E) phases are represented. with almost 21% of total playing time spent frontcrawl sprinting (Platonou & Geladas, 2006), and swimming velocity and its intermittent endurance abilities are essential to players moving successfully in the game (Platonou & Varamenti, 2011), it has been suggested that all players should perform
Kinematic analysis of three water polo front crawl styles 7 Downloaded by [b-on: Biblioteca do conhecimento online UP] at 04:19 13 March 2012 Figure 3. Mean intra-cycle variation of the horizontal velocity of the centre of mass for all participants during one stroke cycle for front crawl performed with head under water (continuous line), head above water (dashed line), and when leading the ball (dotted line). The vertical parallel lines denote the standard deviation for each mean curve. The entry/catch, pull, push, and recovery phases are identified vertically for right and left arms. swimming velocity training, although with adjustments to their abilities (Platonou, 2009). The front crawl styles with head under and above water presented similar values of stroke frequency and length. From the data of Zamparo and Falco (2010), it was clear that front crawl with head under water imposes shorter stroke frequency and longer stroke length than front crawl with head above water, which seems to be related to the need of players to keep the elbows high, increasing stroke frequency, and decreasing stroke length. When front crawl when leading the ball was compared with the other two styles, greater stroke frequency and shorter stroke length were observed for the former. Since velocity was similar among the three styles, it seems that water polo players adjust their stroke frequency and length to perform the water polo front crawl when leading the ball according to the best hydrodynamic characteristics, as previously observed for elite swimmers in sprint bouts (Chollet et al., 2000; McCabe et al., 2011). According to Dopsaj et al. (2007), front crawl when leading the ball represents a skill of high motor complexity, which was also noted by Lupo et al. (2009) when comparing the frequency of horizontal swimming with the ball between recreational and young water polo players. In three-dimensional kinematic analyses, the action of the upper limbs has usually been described using the underwater trajectory of the hand in front crawl (Cappaert, 1999; Deschodt et al., 1999; McCabe et al., 2011). The present study represents the first attempt at a more detailed description of the water polo front crawl styles, through quantification of upper limb coordination. The different front crawl styles did not influence horizontal, vertical, and lateral upper limb position and displacement, except for maximal finger depth, which was greater for front crawl with head under water than for the other styles. Cappaert (1999) reported that front crawl sprint swimmers used a deeper pulling pattern than longdistance swimmers. The front crawl with head under water also presented greater elbow angle at the midstroke position than the two other styles. Previous research found that sprinters tend to have a larger elbow angle than distance swimmers (Cappaert, 1999). However, McCabe et al. (2011) recently claimed that sprint and distance elite swimmers used similar elbow angles and suggested coaches do not encourage both specialists to pull with different elbow angle during the stroke cycle. Water polo players swimming the front crawl with head under water held their arms at a more obtuse angle, probably to increase the propulsion to overcome active drag. This has been observed in proficient swimmers to achieve greater velocity (Seifert, Toussaint, Alberty, Schnitzler, & Chollet, 2010). For trunk obliquity and maximal right and left foot depth, the front crawl with head under water showed lower values than the other two styles. The greater inclination of the trunk in front crawl with head above water has been previously verified by Zamparo and Falco (2010), and seems to imply greater foot depth. Although these findings might be considered a consequence of the specificity of the water polo
Downloaded by [b-on: Biblioteca do conhecimento online UP] at 04:19 13 March 2012 8 K. de Jesus et al. front crawl styles performed with head above water, the reduction of drag is also obtained by the action of the legs in an optimal hydrodynamic position (Deschodt et al., 1999), and should be considered by coaches to avoid swimmers excessive inclined positions during kick actions in front crawl styles. Indeed, the front crawl styles performed with head above water, by increasing the body cross-sectional area, implies greater hydrodynamic resistance and greater mechanical power compared with head under water (Gatta et al., 2010; Zamparo & Falco, 2010). In the current study, water polo players were able to compensate the greater trunk obliquity of the front crawl styles performed with head above water with a higher kick stroke frequency, and similar right and left foot amplitude; this was not observed by Zamparo and Falco (2010) in young female athletes, which could be explained by the greater specialization of the sample in the current study. According to Platonou (2005) and Platonou and Varamenti (2011), water polo is characterized by sudden starts and stops dependent on the explosive power of the legs, which seems to highlight in particular the relevance of kick actions for locomotion purposes. Similar values were observed for the three front crawl styles regarding index of coordination and intra-cycle velocity variation of the centre of mass. The propulsive continuity of the two arms, as denoted by a higher index of coordination values, seems to result in low and stable intra-cycle velocity variation of the centre of mass for the three styles studied (cf. Figure 3), as previously observed in skilled swimmers (Seifert et al., 2010). In the present study, players seemed to reduce the non-propulsive phases (i.e. entry and catch phases) to favour the time dedicated to the propulsive phases (i.e. pull and push phases) within a stroke cycle, employing the superposition coordination mode in each of the three styles as the main way to overcome the forward resistance and reach high velocities (Chollet et al., 2000; Seifert et al., 2010). Since elite swimmers are able to achieve index of coordination values closer to (or even higher than) zero at high velocities (Chollet et al., 2000; Seifert et al., 2010), the superposition mode could also be expected to be employed by proficient water polo players, independent of the style performed, since sprint swimming has been reported to account for approximately 12 30% of the total distance covered during a match (Tan et al., 2009). Conclusions The three front crawl styles showed some kinematic differences, most of which were evidenced between front crawl with head under water and the two other styles. Despite the effect of different styles of front crawl technique on some kinematic parameters, water polo players were able to adapt their interarm coordination to maintain propulsive continuity and minimize intra-cycle variation of the horizontal velocity of the centre of mass during the three studied styles. Findings suggest that as competitive swimmers learn how to swim efficiently by improving swimming technique, water polo players also tend to specialize in propelling themselves with the head above water in the most efficient way. In terms of technique development, there was no evidence from this study to suggest that the technique of the three water polo front crawl styles needs to be developed differently, although leg kick specific exercises for water polo front crawl performed with head above water might be advised during training sessions to overcome the theoretical increase of water resistance, focusing on higher swimming efficiency and better performance. Acknowledgements Thanks to Pedro Gonçalves for technical support and Daniel Fernandes for the drawings. References Abdel-Aziz, Y. I., & Karara, H. M. (1971). Direct linear transformation from comparator coordinates into object space coordinates in close range photogrammetry. In Proceedings of the American Society of Photogrammetry Symposium on Close Range Photogrammetry (pp. 1 18). Falls Church, VA: American Society of Photogrammetry. Bland, J. M., & Altman, D. G. (1986). Statistical methods for assessing agreement between two methods of clinical measurement. Lancet, 1, 307 310. Cappaert, J. M. (1999). Biomechanics of swimming analysed by three-dimensional techniques. In K. Keskinen, P. Komi, & A. P. Hollander (Eds.), Biomechanics and medicine in swimming: Proceedings of the VIII International Symposium on Biomechanics and Medicine in Swimming (pp. 141 145). Jyväskylä: University of Jyväskylä Press. Chollet, D., Charlies, S., & Chatard, J. C. (2000). A new index of coordination for the crawl: Description and usefulness. International Journal of Sports Medicine, 21, 54 59. Clarys, J. P., Jiskoot, J., & Lewillie, L. (1976). A kinematographical, electromyographical and resistance study of water polo and competition front crawl. Swim Technique, 13, 90 92. De Leva, P. (1996). Adjustments to Zatsiorsky-Seluyanov s segment inertia parameters. Journal of Biomechanics, 29, 1223 1230. Deschodt, V. J., Arsac, L. M., & Rouard, A. H. (1999). Relative contributions of arms and legs in humans to propulsion in 25-m sprint front-crawl swimming. European Journal of Applied Physiology, 80, 192 199. Dopsaj, M., Madic, D., & Okicic, T. (2007). The assessment of the acquisition of various crawl style modes in water polo players with respect to age and competitive levels. Physical Education and Sport, 5, 109 120. Escalante, Y., Saavedra, J. M., Mansilla, M., & Tella, V. (2011). Discriminatory power of water polo game-related statistics at the 2008 Olympic Games. Journal of Sports Sciences, 29, 291 298.
Kinematic analysis of three water polo front crawl styles 9 Downloaded by [b-on: Biblioteca do conhecimento online UP] at 04:19 13 March 2012 Ferragut, C., Abraldes, J. A., Vila, H., Rodrígues, N., Argudo, F. M., & Fernandes, R. J. (2011). Anthropometry and throwing velocity in elite water polo by specific playing positions. Journal of Human Kinetics, 27, 31 44. Figueiredo, P., Vilas-Boas, J. P., Maia, J., Gonçalves, P., & Fernandes, R. J. (2009). Does the hip reflect the centre of mass swimming kinematics? International Journal of Sports Medicine, 30, 779 781. Gatta, G., Fantozzi, S., Cortesi, M., Patti, F., & Bonifazi, M. (2010). The mechanical power output in water polo game: A case report. In P. L. Kjendlie, R. K. Stallman, & J. Cabri (Eds.), Biomechanics and medicine in swimming: Proceedings of the XIth International Symposium on Biomechanics and Medicine in Swimming (pp. 84 86). Oslo: Norwegian School of Sport Science. Lupo, C., Tessitore, A., Cortis, C., Ammendolia, A., Figura, F., & Capranica, L. (2009). A physiological, time motion, and technical comparison of youth water polo and Acquagoal. Journal of Sports Sciences, 27, 823 831. McCabe, C. B., Psycharakis, S., & Sanders, R. (2011). Kinematic differences between front crawl sprint and distance swimmers at sprint pace. Journal of Sports Sciences, 29, 115 123. Platonou, T. (2005). On-water dryland vertical jump in water polo players. Journal of Sports Medicine and Physical Fitness, 45, 26 31. Platonou, T. (2009). Cardiovascular and metabolic requirements of water polo. Serbian Journal of Sports Science, 3, 85 97. Platonou, T., & Geladas, N. (2006). The influence of game duration and playing position on intensity of exercise during match-play in elite water polo players. Journal of Sports Sciences, 24, 1173 1181. Platonou, T., & Nikolopoulos, G. (2003). Physiological demands of water polo games with different levels of competitiveness. In J. C. Chatard (Ed.), Biomechanics and medicine in swimming: Proceedings of the IXth International Symposium on Biomechanics and Medicine in Swimming (pp. 493 497). Saint Etienne: University of Saint Etienne. Platonou, T., & Varamenti, E. (2011). Relationships between anthropometric and physiological characteristics with throwing velocity and on water jump of female water polo players. Journal of Sports Medicine and Physical Fitness, 51, 185 193. Seifert, L., Toussaint, H. M., Alberty, M., Schnitzler, C., & Chollet, D. (2010). Arm coordination, power and swim efficiency in national and regional front crawl swimmers. Journal of Human Movement Science, 29, 426 439. Smith, H. M. (1998). Applied physiology of water polo. Sports Medicine, 26, 317 334. Tan, F., Polglaze, T., & Dawson, B. (2009). Activity profiles and physical demands of elite women s water polo match play. Journal of Sports Sciences, 27, 1095 1104. Zamparo, P., & Falco, S. (2010). Head out swimming in water polo: A comparison with front crawl in young female players. In P. L. Kjendlie, R. K. Stallman, & J. Cabri (Eds.), Biomechanics and medicine in swimming: Proceedings of the XIth International Symposium on Biomechanics and Medicine in Swimming (pp. 187 190). Oslo: Norwegian School of Sport Science. Zatsiorsky, V., & Seluyanov, V. (1983). The mass and inertia characteristics of the main segments of the human body. In H. Matsui & K. Kobayashi (Eds.), Biomechanics VIII-B (pp. 1152 1159). Champaign, IL: Human Kinetics.