The performances of the women's 200 m backstroke at the Sydney Olympic games (final and semi-final) were studied using 12 video cameras. For each 50 m lap, the velocities, stroke frequency, strokc length, and turn velocities were calculated using a specific competition analysis computer program. The medallists swam faster than the non-medallists finalist in all four laps. They had a higher stroke frequency and longer stroke length throughout the race. For the whole group (n = 16), the 200 m backstroke velocity was mainly related to the third lap (r = 0.95, 

Chatard, J.

Cossor, J.

Girold, S.

Mason, B.

English

ISBS (International Society of Biomechanics in Sports): Conference Proceedings Archive

Biomechanics Symposla 2001 / Un~verslfy of San Franciscv SPECIFIC STRATEGY FOR THE MEDALISTS VERSUS FINALISTS AND SEMI FINALISTS IN THE WOMEN'S 200 M BACKSTROKE AT THE SYDNEY OLYMPIC GAMES Jean-Claude ~hatard ' ,  Sebastien Girold', Jodi Cosso? and Bruce MasonZ 1 Laboratoire de Physiologie, GIP Exercice, CHU de Saint-Etienne, France Biomechanics Department, Australian Institute of Sports, Canberra, Australia The performances of the women's 200 m backstroke at the Sydney Olympic games (final and semi-final) were studied using 12 video cameras. For each 50 m lap, the velocities, stroke frequency, strokc length, and turn velocities were calculated using a specific competition analysis computer program. The medallists swam faster than the non-medallists finalist in all four laps. They had a higher stroke frequency and longer stroke length throughout the race. For the whole group (n = 16), the 200 m backstroke velocity was mainly related to the third lap (r = 0.95, p<0.01). For the stroke frequency and stroke length. 3 different sb-ategies were observed. The faster swimmers swam with a high stroke frequency and a low stroke length while the slower swimmers did the opposite. KEY WORDS: swimming, biomechanics, performance, Olympics INTRODUCTION: The purpose of this study was to identify whether there was a specific strategy for the medallist, compared to finalists and semi-finalists at the Olympics. The start phase, velocity, stroke frequency, stroke length and turns were studied for each lap throughout the race and related to the final result. METHODS: Subjects. Sixteen swimmers were studied. They consisted of the swimmers that qualified from the heats to the semi-finals. Out of these 16 swimmers, 8 swam the final, and 3 were medallists. Data Collection. During the Sydney 2000 Olympic Games, the 200 m backstroke was analyzed using a total of 12 video cameras. Eight of these cameras were located on the catwalk that ran above the center lanes of the pool, positioned approximately 18 m above pool deck. Seven of the cameras were Sony TRV-9OOE digital cameras operating at 50 Hz. The high speed camera was a Motion Scope PC1 1000 S Mono high speed camera operating at 125 Hz. Following is a list of the cameras used and their positions: 1. 7.5 m from the start - looks at the first 15 m of the race (all lanes) 2. High speed camera at the 7.5 m mark to obtain more information on the race start (middle 3 lanes only) 3. 12.5 m from the start - looks at lanes 1-4 between 5 m and 20 m 4. 12.5 m from the start - looks at lanes 5-8 between 5 m and 20 m 5. 25 m - to obtain accurate information on the 25 m splits for each swimmer (all lanes) 6. 37.5 m from the start - looks at lanes 1-4 between 30 m and 45 m 7. 37.5 m from the start - looks at lanes 5-8 between 30 m and 45 m 8. 42.5 m from the start - looks at the turns (all lanes) Two Sony lipstick cameras operating at 25 Hz were located beneath the pool with one at approximately 5 m from the wall at one end and the other at 12 m. These cameras covered the view from 5 m to 15 m for most of the lanes of the pool to give depth information on the starts and turns. The last two cameras were located in the gantry above the first level of spectator seating and were positioned at the 25 m mark. These cameras were the Sony PCIOOE model (25 Hz) that were operated remotely by staff members in the analysis room using BNC cables over a length of approximately 140 m. Four cables were used for each camera to operate the tilt and pan functions. These cameras were connected to a laptop computer via an A-D card. These cameras were used to check the consistency of the information that was being produced by the digitalization process. Each camera could only compute the analysis information for 1 lane in a Biomechanics Synlposia 2001 /University of San Francisco The competition analysis computer program could perform analysis was capable on all swimmers from any heat and lane. Variables that were determined from the competition analysis included the start time (time from the gun until the swimmer's head passed through the 15 m mark) and turn time (period from the swimmer's head passing the 7.5 m mark on his way into the wall and then return to this point after having completed the turn). Finish time was defined as the time that it took for the swimmer's head to pass under the flags (5 m from the wall) until the swimmer's hands touched the wall at the end of the race. The performance was also divided into 25 m sections in order to accurately determine the velocity through different phases of the race. Swimming velocity was measured for each 25 m section of the race while the free swimming time was the time within a 25 m section that did not include any start, turn or finish sections. Stroke length (meters) and stroke frequency (number of arm stroke cycles per minute) were also calculated in each free swimming section of the race. Stroke length was defined as the distance that a swimmer travels for a complete arm stroke cycle (right hand entry to right hand entry). The number of stroke cycles that would occur in one minute if the present rating was continued was defined as the stroke frequency. The stroke length and interval velocity were calculated using two different methods and a comparison between the results of each was made. If the information provided by both methods was within a pre-determined variance, the analysis was accepted for the interval timing option and information was computed for the next race section. The first method of calculation was from the interval timing option. This used the race timing at the known locations e.g. 15 m mark from the start and the 25 m for the first race section. The distance and times were known, so the velocity could be calculated for this interval. The stroke frequency could only be calculated using the digitizing option where the operator digitizes the swimmer's head at hand entry and then counts a number of strokes before digitizing the head at the same position in the stroke. Digitizing the head provided both the location of the swimmer in the pool and the race time at that location. Using this stroke frequency and the velocity calculated from the known distances and times, it was possible to calculate the stroke length using the formula V = SL x SF. The second method of calculating the stroke length and interval velocity was to involve the use of the stroke digitizing option, which was described to calculate the stroke frequency. Statistical Methods. Means and standard deviations were computed for all variables. A one- way ANOVA was used to compare the results of the medallists to the non-medallist finalists and the semi-finalists. For the whole group, single and stepwise regressions were calculated between the 200 m backstroke velocity (independent variable) and the other studied variables (dependent variable) using the Stat View 512+ program. In the stepwise regressions only the variables that added significantly to the prediction equation were retained. The cluster method of analysis was used to define the three main technique strategies used by the swimmers. In all statistical analyses, the 0.05 level of significance was adopted. RESULTS: The comparisons of the main variables between the medallists, non-medallist finalists and semi-finalists are presented in the Table 1. The medallists swam significantly faster than the non-medallists finalists in the four 50 m laps of the race. They had a higher stroke frequency and a shorter stroke length throughout the race. The three turns velocities were not statistically different within the three groups. For the whole group (n = 16). the 200 m velocity was related to the velocity of the three last 50 m laps (r = 0.93; 0.95 (Figure I )  and 0.85; respectively, p < 0.01). There was no relationship with the first 50 m velocity (r = 0.39, p = NS) (Figure I ) ,  the start velocity (r = 0.33; p = NS), and the 2 first turns velocities (r = 0.16 and 0.09, p = NS). However, it was related to the third turn velocity (r = 0.60, p < 0.01). Biomechanics Sympos~a 2001 /University of San Francisco Table 1 Comparison of the Main Studied Variables (mean f SD) between the Medallists (M), the Non-Medallist Finalists (NM-F) and the Semi-Finalists (SF) M NM-F SF N = 3 N = S  N = 8  200 m velocity (m.s-I) Start velocity (m.s-I) 50(1) velocity (m.s-I) 50(2) velocity (m.s-I) 50(3) velocity (m.s-I) 50(4) velocity (m.s-I) 50(1) SF (cycle.min-I) 50(2) SF (cycle.min-I) 50(3) SF (cycle.min-I) 50(4) SF (cycle.min-I) 50(1) SL (m.cycle-I) 50(2) SL (m.cycle-I) 50(3) SL (m.cycle-I) 50(4) SL (m.cycle-I) Turn I (m.s-I \ Turn 2 (m.s-I j 1.59 (0.01 j 1.62 (0.03);' 1.58 (0.04j Turn 3 (m.s-I) 1.57 (0.04) 1.56 (0.04) 1.54 (0.03)"' SF = stroke frequency; SL = stroke length Significant difference between medallists and non medallist finalists. " Significant difference between non-medallist finalist and semi-finalists. *** Significant difference between medallist and semi-finalists. A M 0 NM-F A A A SF Third 50m velocity (m.s-I) First 50m velocity (m.s-I) 1.58 200m backstroke velocity (m.s-I) 200m backstroke velocity (m.s-I) 1.60 r = 0.95 Figure 1 -Relationship between the third 50 m velocity and the 200 m backstroke velocity (left) and the first 50 m velocity and the 200 m backstroke velocity (right). To further investigate the relative importance of these variables, stepwise regression were calculated between the 200 rn backstroke velocity and the 8 separated velocities. The third 50 m lap velocity (V50-3) was the most important factor, while the second 50 rn lap velocity (V50-2) was the second most important factor. It increased significantly the relationship between the 200 m velocity and the V50-4 from 0.95 to 0.98, p < 0.01, following the equation: r = 0.39 Biomechanics Symposia 2001 /University of San Francisco 200 m backstroke velocity = 0.334 (V50-3) + 0.485 (V50-2) + 0.268 The swimming technique (stroke frequency and stroke length) was analyzed by the cluster method to determine the three main technique strategies used by the 16 swimmers (Table 2). T I  consisted of three swimmers, including the gold and silver medallists. It was characterized by an average stroke frequency and stroke length. T2 consisted of only one swimmer, the bronze medallist. It was characterized as the highest stroke frequency and the lowest stroke length. T3 consisted of the 12 other swimmers. It was characterized by the lowest stroke frequency and thehighest stroke length. Table 2 Description of  the Three Main Technique Strategies Used by the 16 Swimmers TI ,  N = 3  T2, N = I  T3, N = 12 Gold and silver Bronze 200 rn velocity (m.s-I) 50(1) SF (cycle.min-I) 50(2) SF (cycle.min-I) 50(3) SF (cycle.min-I) 50(4) SF (cycle.min-I) 50(1) SL (m.cycle-I) 50(2) SL (rn.cycle-I) 50(3) SL (rn.cycle-I) 50(4) SL (m.cycle-I) medallists 1.482 (0.05) 46.6 (2.4) 43.8 (0.2)' 43.1 (0.7)' 43.6 (1.3) 2.01 (0.10) 2.05 (0.07) 2.05 (0.10) 3 0 . 0 9 )  medallist 1.48" 48.70** 45.5** 46" 46.90** 1.93** 1.97** 1.91** 1.84" SF = stroke frequency; SL = stroke length Significant difference between T I  and T2 ** Significant difference between T2 and T3 *** Significant difference between T I  and T3 CONCLUSION: In the women's 200 m breaststroke, the medallists swam faster than the non- medallists finalists in the four 50 m lap. For the whole group (n = 16), the third 50 m was the most important variable of the race. The technique strategy was very different from one swimmer to another. The faster swimmers swam with a high stroke frequency and a low stroke length while the slower swimmers did the inverse. ACKNOWLEDGMENTS: The PfizerIlOC Medical Commission Research on Sport Sciences funded the project "Competition Swimming Analysis at the Sydney Olympic Games". 

SPECIFIC STRATEGY FOR THE MEDALISTS VERSUS FINALISTS AND SEMI FINALISTS IN THE WOMEN'S 200 M BACKSTROKE AT THE SYDNEY OLYMPIC GAMES

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SPECIFIC STRATEGY FOR THE MEDALISTS VERSUS FINALISTS AND SEMI FINALISTS IN THE WOMEN'S 200 M BACKSTROKE AT THE SYDNEY OLYMPIC GAMES

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