analysis of male and female olympic swimmers in the 180 ......analysis of male and female olympic...

INTERNATIONAL JOURNAL OF SPORT BIOMECHANICS, 1990, 6, 187.197

Analysis of Male and Female Olympic Swimmers

in the 180-Meter Events

Patrick Kennedy, Peter Brown, Somadeepti N. Chengalur, and Richard C. Nelson

The performance of male and female swimmers (N= 397) competing in the preliminary heats of the four 100-meter swimming events during the Seoul Olympic Games was videotaped and later analyzed to determine stroke rate (SR) and stroke length (SL). These data were combined with age, height, and final time O;T) values for statistical analyses which included the relationships among these variables, comparison of male and female performance, and assessment of differences in the four events. The results revealed the following ranges of correlations between SR and SL (rs from -0.65 to -0.90), SL and FT (rs from -0.32 to -0.80), height and SL (0.19 to 0.58), and age and FT (-0.16 to - .051). The factor of SL was identified as the dominant feature of successN swimming performance. The men were older and taller, had longer stroke lengths and higher stroke rates (two of four events), and swam faster than the women. The differences in final times across the four events (freestyle fastest, breaststroke slowest) were due to specific combinations of SR and SL, with neither parameter being consistently dominant.

Swimming performance has shown general improvement in recent years, as reflected in Olympic and world records. This is in sharp contrast to other sports such as athletics (track and field) in which records are broken infrequently and most survive over many years. The continued improvement in swimming may be due to better training methods, improvements in stroke biomechanics, increases in the number of competitors worldwide, and improved selection methods. Other factors that may have contributed are the ages of the elite swimmers as well as their body size, especially their height. Related questions of general interest include the differences in the performance of men and women and the difference among the four basic swimming strokes or events.

The fundamental components of swimming velocity-stroke rate (SR) and stroke length (SL)-have been the subject of many investigations (e.g., Craig

The authors are with the Biomechanics Laboratory at The Pennsylvania State Univer- sity, University Park, PA 16802.

187

188 Kennedy, Brown, Chengalur, and Nelson

& Pendergast, 1979; Craig, Skehan, Pawelczyk, & Boomer, 1985; East, 1970; Hay, 1978). Some authors reported that similar swimming performance is charac- terized by greater variability in SL than in SR (Craig & Pendergast, 1979; Craig et al., 1985; East, 1970; Hay & Guirnares, 1983). Several factors may influence the relationship between SR and SL and therefore affect swimming speed. Among these are anthropometric parameters shown to be related to stroke rate and, more importantly, stroke length (Clarys, Jiskoot, Rijken, & Brouwer, 1974; DeGaray, Levine, & Carter, 1974; Grirnston & Hay, 1986). Grimston and Hay (1986) sug- gested that swimming velocity is little influenced by the swimmer's physique, but the combination of SL and SR used to attain a given swimming velocity is very much a function of body size. However, previous investigators (Katch & Michael, 1973; Poe, 1969; Shotwell, 1972; Smith, 1959, 1978; Stroup, 1964) have reported low correlations between height and final time (FT) for both males and females.

Two additional aspects of swimming performances at the world class level deserve further investigation. First, elite male swimmers usually swim faster (about 10% on average) than their female counterparts. It is of interest to document and evaluate the differences in age, height, and swimming parameters between a large sample of male and female Olympic level swimmers. East (1970) in his comparison of males and females in the same swimming event found that males had longer stroke lengths but similar stroke rates. He concluded that the longer stroke length produced by men was most likely the result of greater propulsive force. A number of investigators have indicated that greater swimming speeds attained by males are due to greater stroke lengths. Typically females and males have similar stroke frequencies (East, 1970; Craig et al., 1985-excluding freestyle). Second, it is also apparent that the velocities produced by the four strokes are clearly different. For example, times in the freestyle event are much faster than those of the other three events, with the breaststroke being the slowest. There is general agreement among investigators that the mean stroke frequencies for freestyle, butterfly, and breaststroke are very similar and that differences in stroke length determine the differences in the final times attained.

The previously reported research investigations concerning these aspects of swimming performance have been limited in a number of ways. The experiments usually consisted of studying a relatively small number of swimmers, of different ability levels, who were evaluated in training sessions rather than in competition. The methods typically used to determine SR and SL have necessarily been primi- tive, based on the use of stopwatches for time variables and visual observations for SR determinations. Many studies were limited to one gender only and to one or two swimming events. To date no study of elite men and women swimmers participating in preliminary and final events in all four swimming strokes in Olympic Games or world championships has been reported. The Olympic swimming competition in the 1988 Summer Games provided a unique opportunity to study the best male and female swimmers in the world. The availability of modem videorecording and analysis techniques made it possible to capitalize on this opportunity.

The basic data for the analytical part of this study consisted of the age, height, stroke rate (SR), stroke length (SL), and final time (FT) for the male and female competitors in the 100-meter preliminary swimming events. The purposes of the study were as follows: (a) to evaluate the intercorrelations among the five experi-

Male and Female Olympic Swimmers 189

mental variables for men and women, (b) to compare and contrast the male and female swimmers, and (c) to examine the differences across the four swimming events. The subjects included a total of 397 Olympic swimmers, 221 men and 176 women.

Methods

The swimming events at the Seoul Olympic Games, September 19-26,1988, were videotaped by a three-man crew from the Biomechanics Laboratory of Penn State University. All preliminary and final heats were recorded for both men and women, with the exception of the 1500-m freestyle for men. The events analyzed in this study were the men's and women's 100-m preliminary heats for backstroke, breaststroke, butterfly, and freestyle.

The recording procedures involved three Panasonic AG-450 S-VHS video cameras located above the top row of spectator seats. The first camera was posi- tioned to cover the start and first 10 meters, the second was used to pan the complete race, while the third recorded the final 10 meters to include the turns. This study utilized recordings from only the panning camera, which was located 20 meters above and 50 meters from the near side of the pool at the midway point. From this fixed position the panning the camera was able to capture all of the swimmers during the 100-m races. The pool was divided into 10 lanes by floating buoys that alternated in color every 5 meters and served as calibration markers for distance measurements. The two outside lanes were not used in competition, thereby limiting the maximum number of swimmers per race to eight.

VHS copies of the S-VHS originals were used in the analysis of the swimming events. The recording rate of the AG-450 is 60jeIds per second. The video playback system (Panasonic AG-6300) interlaced two consecutive fields to create a videoframe, thereby producing 30frames per second. This frame rate was considered adequate for this investigation since the motion of swimmers is relatively slow, and only above-water performance was recorded. An AST premium 286 computer, with a BCD Associates video controller circuit board, was interfaced to the video playback system. A program designed by Peak Performance Technologies, Inc., was used to sequentially encode every frame of the tape with a number on audio track 2. When a frame was played back on the AG-6300, the computer was able to detect which frame number was currently being played; thus the time between any two given frames was determined with an accuracy of 1/30th of a second. This method was deemed sufficiently accurate for the data being generated.

Data Analysis

Middle-pool times (TI and T2) were determined for both 50-m laps of a race. This variable was defined as the time required for a swimmer to cover a 30 (Tl) or 35 (T2) meter distance (excluding the start and turn) using only the specific swimming stroke. These times were later used in the calculation of average velocity for each lap, which was divided by SR to determine SL values which were averaged to obtain SL; equal weighting was given to each value. The time between the 15-m and 45-m lane markers (30-m distance) during the first length was determined and denoted as TI. This was accomplished by first interpolating along an imaginary line connecting the 15-m markers of each lane, selecting the frame


in which the swimmer's head reached this line, and storing its frame number. The videotape was next paused on the frame in which the swimmer's head reached the 45-m lane marker and a second frame number was stored in the computer. The difference in frame numbers was used to calculate TI. The same procedure was used to determine T2, except that the starting point was set at the 10-m mark, which meant that the distance covered by the swimmer was 35 meters. In a few cases during the backstroke event the swimmers surfaced beyond the 15-m mark for the first lap, which negated the calculation of TI . The angle of the camera view made it necessary to estimate the position of each swimmer's head as it passed the specified lane marker. The experimental errors resulting from this procedure were considered to be small and primarily random in nature.

One method for measuring SR would be to count every cycle of every swimmer over the whole race. However, because of the large number of swimmers in this study it was necessary to develop an alternative method for determining SR. A pilot study was conducted utilizing performance in the finals of the four events (races that were not analyzed in this study). The average SR for each swirn- mer was calculated from the number of cycles completed during T1 and T2. In addition, two-, three-, and four-cycle samples taken over the midsection of the pool were calculated for each swimmer, using the time to complete the specified number of cycles. The mean SR values derived from the first (SR1) and second (SR2) laps were then correlated with the actual SR measured over the respective middle-pool sections. These results indicated that the SR estimates based on the four-stroke cycle method produced the most valid predictions, with correlation coefficients of 0.95 for the breaststroke and 0.99 for the other three events. On the basis of these results it was decided to proceed with the four-stroke cycle method of estimating SR. This offers a practical method of estimating the SR of swimmers in training sessions and during competitions.

The stroke length (SL) values for each lap were calculated from the following basic relationship: V = SR x SL. The middle-pool times over the 30-m (TI) and 35-m (T2) distances were used to calculate velocity values. These were then combined with the previously determined average SR values to derive average SL (SL = VISR) for each lap. These SL values were then used to calculate an average SL for the 100-m race which was used in the data analysis. The official times for the first lap and final times were obtained from the Official Swimming Results of the Seoul Olympics (1988). The name, country, and self-reported age and height data were taken from the list of competitors (Seoul Olympian Entries, 1988).

Statistical Analyses

Once the stroke rate, stroke length, final time, height, and age data for each swimmer were collected, a series of statistical calculations were performed on a Macintosh computer using StatView 512+ software (Abacus Concepts, Inc.). The data from all preliminary races of a given event were combined to form one data base for that particular 100-m event. First the intercorrelations among all variables (age, height, SR, SL, FT) were computed for men and women for each event. A two-tailed test at the .05 level of probability was applied to assess the statistical significance of the calculated correlation values. Two one-way analyses of variance were used to evaluate differences between gender and across events for each variable under investigation. The means and standard deviations for the five experimental variables for men and women are presented in Table 1.

Male and Female Olympic Swimmers

Table 1

Variable Mean and Standard Deviation Values

Age Height SR SL FT N (Y rs) (cm) (Hz) (m) (set)

Males

Backstroke

Breaststroke

Butterfly

Freestyle

Females

Backstroke

Breaststroke

Butterfly

Freestyle

Results

Variable interrelationships

Linear correlations were determined among all five experimental variables. A significance :eve1 of .!I5 was set for the evaluation of these coefficients. Correlation coefficients for all swimming events for both males and females are shown in Tables 2 and 3, respectively. The most striking results were the r values for SR versus SL, which were all highly significant and ranged from -0.65 to -0.90 for men and women together. This shows clearly the interdependence of these two parameters, such that swimmers with high SR values concurrently have short SL, and vice versa. However, the more important question is how each of these relate to actual performance (FT). The correlations between SL and FT are all negative, ranging from -0.32 to -0.80, with aU but the lowest coefficient being statistically significant. This indicates a negative relationship between the length of the swirn- mers' strokes and their final race times: better swimmers have longer stroke lengths. In contrast, the results for SR versus FT indicated that four of the eight r values were near zero. For the men, low and significant positive rs of 0.39 and 0.43 were observed for the butterfly and freestyle events, respectively. How- ever, a significant negative r of -0.39 for the women's backstroke was noted. These mixed results indicate that the precise role of SR in determining swimming performance is unclear since it may be both gender and event specific. On the

Kennedy, Brown, Chengalur, and Nelson

Table 2

Men's Correlation Matrices

Backstroke Stroke rate Stroke length Final time Height

Breaststroke Stroke rate Stroke length Final time Height

Butterfly Stroke rate Stroke length Final time Height

Freestyle Stroke rate Stroke length Final time Height

other hand, the results for SL clearly demonstrate the important role stroke length plays in swimming success.

The factor of age was of greater importance to performance among the women than the men. For the women, three of the four correlations (age vs. FT) were significant (rs ranging from -0.16 to -0.55). Only one of the correlations for men was significant (freestyle, r= -0.51), though two of the remaining three were also negative. The mean age for the females was more than 2 years less than for men, and their standard deviation was also greater, indicating that propor- tionally more of the women were in their teenage years. This may account for the greater influence of age among the women. In any case, these results do indicate a general tendency for the older swimmers to be more successful, especially among the female competitors.

SR was found to be independent of body size, as represented by the height variable. Of the eight correlations, only one was significant (men's butterfly, r= -0.44), suggesting that SR is not linked to body size. In contrast, SL was found to be strongly related to height, with r values ranging from 0.19 to 0.58 (five of the eight rs being significant). Such a result is not unexpected since, in general, taller swimmers would tend to have longer SL values. Finally, the relation


Table 3

Women's Correlation Matrices

Backstroke 39 Stroke rate .32 Stroke length .01 - .74' Final time - .46* - .39* - .32 Height .40 .OO .31

Breaststroke Stroke rate Stroke length Final time Height

Butterfly Stroke rate Stroke length Final time Height

Freestyle 57 Stroke rate .04 Stroke length .22 - .89* Final time - .55* .07 - .51 Height .32 - .25 .40* - .43*

between height and FT revealed a consistent pattern of moderately high correlations (rs from -0.26 to -0.72, with five of them being significant), reflecting the fact that taller swimmers tend to be more successful.

Event and Gender Comparisons

A series of ANOVAs were calculated for comparison of the strokes across the five variables under study. The results have been grouped by gender and appear in Table 4 (men) and Table 5 (women). The data for both men and women indicate no significant differences in age or height for the swimmers in the four events. The SR analysis for both men and women revealed the SR for backstroke to be significantly lower than for all three of the other strokes; however, the differences among the three strokes were small or nonsignificant for three of the six comparisons for both men and women.

The cross-event comparisons for both men and women indicated significantly higher SL values for backstroke than for breaststroke and butterfly, but similar SL values for freestyle. Further, significant differences were found between freestyle, butterfly, and breaststroke, in decreasing order of magnitude. FT for all strokes differed significantly from each other, with the order from fastest to

1 94 Kennedy, Brown, Chengalur, and Nelson

Table 4

Analysis of Variance Results: Men

Comparison Age Height SR SL FT

Backstroke vs. breaststroke n.s. n.s. 20.0 58.4 33.9 Backstroke vs. butterfly n.s. n.s. 12.0 6.3 3.6 Backstroke vs, freestyle n.s. n.s. 9.7 n.s. 29.4 Breaststroke vs. butterfly n.s. n.s. n.s. 25.8 62.2 Breaststroke vs. freestyle n.s. n.s. 2.7 72.2 129.8 Butterfly vs. freestyle n.s. n.s. n.s. 7.7 11.6

Note. Significant differences w .05 ) have Scheffe F value listed; n.s. = no significant difference.

Table 5

Analysis of Variance Results: Women

Comparison Age Height SR SL FT

Backstroke vs. breaststroke n.s. n.s. 18.3 58.8 30.2 Backstroke vs. butterfly n .~ . n.s. 36.3 26.6 n.s. Backstroke vs. freestyle n.s. n.s. 26.4 n.s. 31 .O Breaststroke vs. butterfly n.s. n.s. 3.1 6.4 49.3 Breaststroke vs. freestyle n.s. n.s. n.s. 45.4 134.7 Butterfly vs. freestyle n.s. n.s. n.s. 16.0 16.0

Note. Significant differences w.05) have Scheff6 F value listed; n.s. = no significant difference.

slowest being freestyle, butterfly, backstroke, and breaststroke. One exception to this pattern was the nonsignificant difference between backstroke and butterfly for women. For the men, freestyle mean time was 6.9% faster than butterfly, 11.2% faster than backstroke, and 23.8 % faster than breaststroke. The correspond- ing values for women were 8.6, 12.1, and 25.0 %, respectively.

The final comparisons were made between men and women for each variable at each stroke. These results are presented in Table 6. Significant differences were noted for gender for all comparisons except SR for butterfly and freestyle. The males were significantly older and taller and demonstrated higher SR (two of four events), longer SL, and faster FT.


Analysis of Variance Results: Men vs. Women

Stroke

-- -

Age Height SR SL FT

Backstroke 11.13 45.55 6.92 19.35 76.43 Breaststroke 7.03 93.39 9.18 7.95 103.15 Butterfly 12.36 49.66 n .~ . 68.87 96.24 Freestyle 29.08 78.96 n.s. 30.10 119.15

Note. Significant differences w.05) have Scheffe F value listed; n.s. = no significant difference.

Discussion

The results of this comprehensive investigation of elite swimmers performing in Olympic competition represent an important contribution to the literature on swimming. The relatively large number of swimmers studied through the use of modern video technology in the highly competitive environment of the Olympic Games has provided a valuable data base for future comparisons among swimmers.

The specific findings for the intercorrelation phase of the study included the following: The very high, negative correlations between SR and SL show clearly the interaction between these two parameters which produce swimming velocity. It further indicates that various combinations are used by the swimmek such as high SL and low SR, intermediate values for both, or low SL and high SR. However, further analysis linked SL strongly with performance time for most events (the exception being women's 100-m backstroke), suggesting this to be the dominant feature of swimming velocity. The factor of body size, as reflected in height, was closely associated with SL but not with SR. This is important since SL was shown to be related to final time.

The comparison of males and females indicated the former to be signifcantly taller and older and able to produce greater stroke lengths, higher stroke rates (for two events), and better performance times. The overall FT mean for males versus females across all four events revealed the men to be 10.6% faster. Com- parisons for the other variables indicated that the males were 11.5 % older and 7.3% taller, and that they had 9.7% longer SL but only 1 % greater SR. These findings make it difficult to separate the influence of gender from that of body size. Are the females slower because of their gender or because they are smaller than their male counterparts? One way to answer this question would be to compare a sample of male swimmers of comparable height to that of the elite female swimmers using the experimental variables of this study. This would minimize or eliminate the difference in height between the two groups. However, such a sample of male swimmers may not contain a sufficient number of the elite male swimmers who tend to be taller than the less successful male competitors.


This study is the first such investigation to be conducted during Olympic Games competition and, therefore, represents a valuable resource for future studies. It was based on the video recording of the 100-m events and represents only part of the total research effort. Similar studies of the 200-m and 400-m events and 50-m freestyle are being completed, thereby adding to the Olympic archives of swimming performance.

Conclusions

The following conclusions have been derived from the results of this study of the 100-meter Olympic swimming events:

1. Stroke length is the single most important characteristic of successful competitive swimming over the 100-m distance.

2. Body size is an important determinant of success in these events. 3. Males are superior to females in 100-m swimming performance, due primar-

ily to their greater stature, age, and longer stroke lengths. 4. The differences in final times across events are due to different combinations

of SR and SL rather than to either of these features alone.

References

Clarys, J.P., Jiskoot, J., Rijken, H., & Brouwer, P.J. (1974). Total resistance in water and its relationship to body form. In R.C. Nelson & C.A. Morehouse (Eds.), Bio- mechanics ZV (pp. 187-196). Baltimore: University Park Press.

Craig, A.B., Jr., & Pendergast, D.R. (1979). Relationships of stroke rate, distance per stroke and velocity in competitive swimming. Medicine and Science in Sport, 11, 278-283.

Craig, A.B., Jr., Skehan, P.L., Pawelczyk, J.A., & Boomer, W.L. (1985). Velocity, stroke rate, and distance per stroke during elite swimming competition. Medicine and Science in Sports and Exercise, 17, 625-634.

DeGaray, A.L., Levine, L., & Carter, J.E.L. (1974). Genetic andanthropological studies of Olympic athletes. New York: Academic Press.

East, D.J. (1970). An analysis of stroke frequency, stroke length, and performance. New Zealand Journal of Health, Physical Education and Recreation, 3 , 16-27.

Grimston, S.K., & Hay, J.G. (1986). Relationship among anthropometric and stroking characteristics of college swimmers. Medicine and Science in Sports and Exercise, 18, 60-68.

Hay, J.G. (1978). Swimming. In J.G. Hay, Biomechanics of sport techniques @p. 337-381). Englewood Cliffs, NJ: Prentice-Hall.

Hay, J.G., & Guirnares, A.C.S. (1983, Aug./Oct.). A quantitative look at swimming biomechanics. Swimming Technique, pp. 11-17.

Katch, V.L., & Michael, E.D. (1973). The relationship between segmental leg measurements, leg strength, and relative endurance performance of college females. Hu- man Biology, 45, 371-383.

W c i a l Swimming Results of the XXN Olympiad at Seoul. (1988). Unpublished document. Poe, G.H. (1969). fie relationship of selected anthropometric measurements to swimming

time of college varsity swimmers in the$&-yardfront crawl stroke. Unpublished master's thesis, Springfield College.


Seoul Olympian Ennies (Day 2). (1988, Sept. 15). Published by Seoul Olympic Organizing Committee. Shotwell, F.L. (1972). The relationship of swimming speed to selected physical measurements. Unpublished master's thesis, Texas Technological University.

Smith, L.E. (1959). An investigation into the relationship between learn-to-swim achieve- ment and general motor capacity of boys and girls between the ages of five and eleven years. Australian Physical Education Journal, 16, 5-12.

Smith, L. (1978). Anthropometric measurements and arm and leg speed performance of male and female swimmers as predictors of swim speed. Journal of Sports Medi- cine, 18, 153-168.

Stroup, F. (1964). Height, weight and swimming time. Zhe Physical Educator, 21, 19.

Acknowledgments

The authors wish to express their appreciation to the following persons who assisted with the conduct of this study: Eui-Hwan Kim, Gerald Smith, Gary Scheirrnan, and Carolyn Barbieri. The support of Eastman Kodak Co., Redlake Corp., the International Swimming Federation (FINA), and the Medical Commission of the IOC are gratefully acknowledged.

analysis of male and female olympic swimmers in the 180 ......analysis of male and female olympic...

Documents