Institute of General Practice and for Health Services Research, University of Zurich, Zurich, Switzerland

Cardiovascular Center Cardiology, University Hospital Zürich, Zürich, Switzerland

INSERM U1093, Faculty of Sport Sciences, University of Burgundy, Dijon, France

Gesundheitszentrum St. Gallen, Vadianstrasse 26, 9001 St. Gallen, Switzerland

Abstract

Background

The purpose of the present study was to analyse potential changes in performance of elite breaststroke swimmers competing at national and international level and to compare to elite freestyle swimming performance.

Methods

Temporal trends in performance of elite breaststroke swimmers were analysed from records of the Swiss Swimming Federation and the FINA (Fédération Internationale de Natation) World Swimming Championships during the 1994–2011 period. Swimming speeds of elite female and male breaststroke swimmers competing in 50 m, 100 m, and 200 m were examined using linear regression, non-linear regression and analysis of variance. Results of breaststroke swimmers were compared to results of freestyle swimmers.

Results

Swimming speed in both strokes improved significantly (

Conclusions

The present study showed that elite male and female swimmers competing during the 1994–2011 period at national and international level improved their swimming speed in both breaststroke and freestyle. The sex difference in freestyle swimming speed consistently increased in athletes competing at national level, whereas it remained unchanged in athletes competing at international level. Future studies should investigate temporal trends for recent time in other strokes, to determine whether this improvement is a generalized phenomenon.

Background

Improved understanding of performance by top athletes, including long-term changes and sex-related differences, can help athletes and coaches to estimate performance limits, to choose appropriate training protocols, and to set realistic goals. During the past 30 years, several studies investigated human limits in various sports such as running ^{st} century

For swimmers, changes in performance over time have mainly been investigated in freestyle swimming

The changes in swimming performance have been investigated for freestyle swimmers competing at international top level

The purpose of the present study was to investigate the changes in breaststroke swimming performance in athletes competing at both national and international level and to compare breaststroke swimming performance to freestyle swimming performance. We therefore analyzed changes in freestyle and breaststroke performance of the annual top ten Swiss swimmers (

Methods

Ethics

All procedures used in the study were approved by the Institutional Review Board of Kanton St. Gallen, Switzerland with a waiver of the requirement for informed consent of the participants given the fact that the study involved the analysis of publicly available data.

Subjects and design

Race times on long courses for the annual top ten men and women in breaststroke and freestyle swimming recorded in the Swiss high score list between 1994 and 2011 were obtained per civil year from the website of the Swiss Swimming Federation

Methodology

Since races in breaststroke swimming were held for 50 m, 100 m and 200 m but freestyle races for 50 m, 100 m, 200 m, 400 m, 800 m and 1,500 m, we analysed freestyle swimming races only for 50 m, 100 m, and 200 m to compare with breaststroke swimming results. To allow a comparison of swimming performance for different styles and distances, race times were transformed to swimming speed by dividing race distance by time. To determine temporal trends, we compared the average annual swimming speed for each stroke and race distance, by the top ten Swiss men and top ten Swiss women, and by the eight men and eight women competing in the FINA finals. To analyse the maximum overall swimming performance, we averaged the fastest ten swimming speeds in each stroke for four groups: Swiss women, Swiss men, FINA women, and FINA men. Sex-related differences were calculated using the equation [(women swimming speed) – (men swimming speed)]/(men swimming speed) × 100. The calculation was performed for pairs of equally placed athletes during each year,

Statistical analyses

Prior to statistical analyses, each data set was tested for normal distribution and homogeneity of variances. Normal distribution was tested using a D’Agostino and Pearson omnibus normality test. Homogeneity of variances was tested using a Levene’s test, in cases with two groups, and with a Bartlett’s test, in cases with more than two groups. A potential change in swimming speed across years was investigated using regression analyses. Since the change in sex difference in endurance is assumed to be non-linear ^{nd} to 17^{th} degree were calculated; for swimmers at international level, polynomial regressions from 2^{nd} to 7^{th} degree were calculated. Additionally, LOWESS (

Results

Changes in breaststroke and freestyle swimming speed across the years

Figure

Swimming speeds of Swiss top ten breaststroke swimmers for 50 m (Panel A), 100 m (Panel B) and 200 m (Panel C)

**Swimming speeds of Swiss top ten breaststroke swimmers for 50 m (Panel A), 100 m (Panel B) and 200 m (Panel C).** Results are presented as mean ± SD.

Swimming speeds of Swiss top ten freestyle swimmers for 50 m (Panel A), 100 m (Panel B) and 200 m (Panel C)

**Swimming speeds of Swiss top ten freestyle swimmers for 50 m (Panel A), 100 m (Panel B) and 200 m (Panel C).** Results are presented as mean ± SD.

Swimming speeds of breaststroke FINA finalists for 50 m (Panel A), 100 m (Panel B) and 200 m (Panel C)

**Swimming speeds of breaststroke FINA finalists for 50 m (Panel A), 100 m (Panel B) and 200 m (Panel C).** Results are presented as mean ± SD.

Swimming speeds of freestyle FINA finalists for 50 m (Panel A), 100 m (Panel B) and 200 m (Panel C)

**Swimming speeds of freestyle FINA finalists for 50 m (Panel A), 100 m (Panel B) and 200 m (Panel C).** Results are presented as mean ± SD.

**Kind of regression**

**Sum of Squares**

**DOF**

**AICC**

**Best regression AIC-Test**

**Best regression F-Test**

**Delta**

**Probability**

**Likelihood**

For all distances, the changes in swimming speed were linear.

50 m breaststroke

polynomial

0.0035

12

−138.34

linear

linear

2.80

0.19

80.3%

male Swiss swimmers

linear

0.0062

16

−141.15

100 m breaststroke

polynomial

0.0009

0

−144.16

linear

undetermined

5.72

0.054

94.6%

male Swiss swimmers

linear

0.0038

16

−149.88

200 m breaststroke

polynomial

0.0011

0

−139.69

linear

undetermined

13.48

0.0011

99.88%

male Swiss swimmers

linear

0.0032

16

−153.17

50 m breaststroke

polynomial

0.0011

0

−140.12

linear

undetermined

6.62

0.035

96.5%

female Swiss swimmers

linear

0.0045

16

−146.74

100 m breaststroke

polynomial

0.0018

0

−131.76

linear

undetermined

29.91

3.19 e^{−07}

100%

female Swiss swimmers

linear

0.0019

16

−161.67

200 m breaststroke

polynomial

0.0014

0

−135.81

linear

undetermined

22.41

1.35 e^{-05}

99.99%

female Swiss swimmers

linear

0.0024

16

−158.22

**Kind of regression**

**Sum of Squares**

**DOF**

**AICC**

**Best regression AIC-Test**

**Best regression F-Test**

**Delta**

**Probability**

**Likelihood**

For all distances, the changes were linear.

50 m freestyle

polynomial

0.0067

0

−108.11

linear

undetermined

29.06

4.87 e^{-07}

100%

male Swiss swimmers

linear

0.0077

16

−137.18

100 m freestyle

polynomial

0.0002

2

−45.86

linear

linear

21.05

2.67 e^{-05}

99.99%

male Swiss swimmers

linear

0.0013

6

−66.92

200 m freestyle

polynomial

0.0015

0

−134.90

linear

linear

32.22

1.005 e^{-07}

100%

male Swiss swimmers

linear

0.0014

16

−167.13

50 m freestyle

polynomial

0.0016

0

−132.88

linear

undetermined

27.20

1.23 e^{-06}

99.99%

female Swiss swimmers

linear

0.0021

16

−160.08

100 m freestyle

polynomial

0.0027

0

−124.34

linear

undetermined

28.91

5.26 e^{-07}

99.99%

female Swiss swimmers

linear

0.0031

16

−153.25

200 m freestyle

polynomial

0.0006

0

−152.27

linear

undetermined

14.68

0.00064

99.93%

female Swiss swimmers

linear

0.0014

16

−166.95

**Kind of regression**

**Sum of Squares**

**DOF**

**AICC**

**Best regression AIC-Test**

**Best regression F-Test**

**Delta**

**Probability**

**Likelihood**

For all distances, the changes were linear.

50 m breaststroke

polynomial

0.00042

1

−9.35

linear

linear

35.83

1.65 e^{-08}

100%

male FINA finalists

linear

0.00190

4

−45.19

100 m breaststroke

polynomial

0.00035

2

−40.28

linear

linear

23.83

6.66 e^{-06}

99.99%

male FINA finalists

linear

0.00180

6

−64.12

200 m breaststroke

polynomial

0.00014

2

−47.16

linear

linear

23.19

9.18 e^{-06}

99.99%

male FINA finalists

linear

0.00086

6

−70.35

50 m breaststroke

polynomial

0.00027

0

−49.89

linear

undetermined

1.51

0.31

68.04%

female FINA finalists

linear

0.00069

4

−51.41

100 m breaststroke

polynomial

0.00034

2

−40.31

linear

linear

30.66

2.19 e^{-07}

100%

female FINA finalists

linear

0.00080

6

−70.97

200 m breaststroke

polynomial

8.76 e^{-05}

2

−51.37

linear

linear

18.04

0.00012

99.98%

female FINA finalists

linear

0.00097

6

−69.41

**Kind of regression**

**Sum of Squares**

**DOF**

**AICC**

**Best regression AIC-Test**

**Best regression F-Test**

**Delta**

**Probability**

**Likelihood**

The changes were linear for all distances.

50 m freestyle

polynomial

0.00061

2

−35.82

linear

linear

23.53

7.76 e^{-06}

99.99%

male FINA finalists

linear

0.00340

6

−59.35

100 m freestyle

polynomial

0.00017

2

−45.86

linear

linear

32.22

1.005 e^{−07}

100%

male FINA finalists

linear

0.00130

6

−66.92

200 m freestyle

polynomial

0.00020

2

−44.73

linear

linear

23.55

7.69 e^{-06}

99.99%

male FINA finalists

linear

0.00110

6

−68.28

50 m freestyle

polynomial

0.00039

2

−39.26

linear

linear

18.46

9.76 e^{-05}

99.99%

female FINA finalists

linear

0.00420

6

−57.73

100 m freestyle

polynomial

0.00019

2

−44.78

linear

linear

22.05

1.62 e^{-05}

99.99%

female FINA finalists

linear

0.00130

6

−66.84

200 m freestyle

polynomial

1.58 e^{-05}

2

−65.03

linear

polynomial

1.24

0.34

65.08%

female FINA finalists

linear

0.00140

6

−66.27

In breaststroke, male Swiss swimmers increased their swimming speed by 0.008 m · s^{−1}, 0.004 m · s^{−1}, and 0.005 m · s^{−1}
^{−1}, 0.004 m · s^{−1}, 0.004 m · s^{−1}
^{−1}
^{−1}, 0.004 m · s^{−1}, 0.003 m · s^{−1}
^{−1}, 0.008 m · s^{−1}, and 0.005 m · s^{−1}
^{−1}
^{−1}, 0.005 m · s^{−1}, and 0.004 m · s^{−1}
^{−1}, 0.004 m · s^{−1}, and 0.003 m · s^{−1}

Sex differences in breaststroke and freestyle swimming speed

Men swam consistently faster than women for both strokes and all distances. In Swiss swimmers, swimming speed in breaststroke showed no changes across years (Figure

Sex differences of Swiss top ten breaststroke swimmers for 50 m (Panel A), 100 m (Panel B) and 200 m (Panel C)

**Sex differences of Swiss top ten breaststroke swimmers for 50 m (Panel A), 100 m (Panel B) and 200 m (Panel C).** Results are presented as mean ± SD.

Sex differences of Swiss top ten freestyle swimmers for 50 m (Panel A), 100 m (Panel B) and 200 m (Panel C)

**Sex differences of Swiss top ten freestyle swimmers for 50 m (Panel A), 100 m (Panel B) and 200 m (Panel C).** Results are presented as mean ± SD.

Sex differences of breaststroke FINA finalists for 50 m (Panel A), 100 m (Panel B) and 200 m (Panel C)

**Sex differences of breaststroke FINA finalists for 50 m (Panel A), 100 m (Panel B) and 200 m (Panel C).** Results are presented as mean ± SD.

Sex differences of freestyle FINA finalists for 50 m (Panel A), 100 m (Panel B) and 200 m (Panel C)

**Sex differences of freestyle FINA finalists for 50 m (Panel A), 100 m (Panel B) and 200 m (Panel C).** Results are presented as mean ± SD.

Comparison of sex differences in swimming speeds of the top ten Swiss breaststroke and freestyle swimmers for 50 m, 100 m and 200 m

**Comparison of sex differences in swimming speeds of the top ten Swiss breaststroke and freestyle swimmers for 50 m, 100 m and 200 m.** Results are presented as mean ± SD.

Comparison of sex differences in swimming speeds of FINA finalists in breaststroke and freestyle for 50 m, 100 m and 200 m

**Comparison of sex differences in swimming speeds of FINA finalists in breaststroke and freestyle for 50 m, 100 m and 200 m.** Results are presented as mean ± SD.

**Kind of regression**

**Sum of Squares**

**DOF**

**AICC**

**Best regression AIC-Test**

**Best regression F-Test**

**Delta**

**Probability**

**Likelihood**

The changes were linear for all distances.

50 m breaststroke

polynomial

10.02

0

23.45

linear

undetermined

21.71

1.92 e^{-5}

99.99%

Swiss swimmers

linear

17.49

16

1.73

100 m breaststroke

polynomial

2.78

0

0.40

linear

linear

13.75

0.0010

99.89%

Swiss swimmers

linear

7.56

16

−13.35

200 m breaststroke

polynomial

3.80

0

6.03

linear

undetermined

22.42

1.34 e^{-5}

99.99%

Swiss swimmers

linear

6.38

18

−16.39

50 m freestyle

polynomial

7.20

0

17.51

linear

undetermined

24.94

3.83 e^{-6}

99.99%

Swiss swimmers

linear

10.51

16

−7.42

100 m freestyle

polynomial

3.93

13

−16.30

linear

linear

1.30

0.34

65.7%

Swiss swimmers

linear

5.97

16

−17.61

200 m freestyle

polynomial

1.90

0

−6.42

linear

undetermined

18.32

0.00010

99.98%

Swiss swimmers

linear

4.01

16

−24.74

**Kind of regression**

**Sum of Squares**

**DOF**

**AICC**

**Best regression AIC-Test**

**Best regression F-Test**

**Delta**

**Probability**

**Likelihood**

The changes were all linear.

50 m breaststroke

polynomial

0.037

1

17.53

linear

linear

23.80

6.75 e^{-6}

99.99%

FINA finalists

linear

1.27

4

−6.26

100 m breaststroke

polynomial

0.17

2

9.28

linear

linear

15.80

0.00036

99.96%

FINA finalists

linear

2.53

6

−6.51

200 m breaststroke

polynomial

0.21

3

−7.73

linear

linear

3.24

0.16

83.5%

FINA finalists

linear

1.45

6

−10.98

50 m freestyle

polynomial

0.16

2

9.13

linear

linear

20.57

3.41 e^{-5}

99.99%

FINA finalists

linear

1.37

6

−11.44

100 m freestyle

polynomial

0.56

0

−7.19

linear

undetermined

3.61

0.14

85.9%

FINA finalists

linear

1.48

6

−10.81

200 m freestyle

polynomial

0.60

0

−6.60

linear

undetermined

6.38

0.039

96.1%

FINA finalists

linear

1.13

6

−12.98

Interaction between style and sex

Based on the fastest breaststroke and freestyle swimmers, swimming style and sex had a significant interactive effect on swimming speed for both Swiss (F = 15.13, Dfn = 1, DFd = 2156,

**Speed of Swiss swimmers (m/s)****
*
**

**Speed of FINA swimmers (m/s)****
**
**

**Breaststroke**

**Freestyle**

**Breaststroke**

**Freestyle**

All main effects of stroke and sex on swimming speed were highly significant (2-way ANOVA,

Men

1.50 ± 0.12

1.91 ± 0.15

1.64 ± 0.10

2.06 ± 0.16

Women

1.33 ± 0.09

1.70 ± 0.11

1.47 ± 0.10

1.84 ± 0.13

Discussion

The present study examined temporal changes in breaststroke swimming speed for top Swiss and FINA finalists and compared to freestyle swimming speed. The results showed that (

Temporal changes in breaststroke and freestyle swimming speed

The increased swimming speed of women and men in freestyle and breaststroke swimming during the 1994–2011 period as well as the new world records during the 2012 Olympic Games

In addition to technological advances, swimming speed during the 1994–2011 period could have been affected by changes in anthropometric and physiological characteristics ^{th} century found an increase of 1–2 cm in body height and 0.5-1.5 kg in body weight per decade

Sex differences in breaststroke and freestyle swimming

Results of previous studies reporting that the difference between men and women’s world freestyle records remained stable during the past 60 years

Sex-related differences in performance are largely explained by sex-specific differences in body dimensions, swimming speed, buoyancy, stroke mechanics, stroke length, starts and turn time, basic and specific endurance, anaerobic power and capacity, muscle power, and flexibility ^{st} century following the introduction of new technological swim suits were greater for men than for women in freestyle swimming, while the gains in breaststroke was similar for the two sexes

The stable sex difference at international level is in agreement with previous investigations

There is also indirect evidence that the sex-related difference might be different in breaststroke compared to freestyle swimming. Active drag coefficient (C_{d}) as a measure of technique and performance was lower for faster swimmers _{d} was similar for men and women in freestyle swimming, but that women had a significantly lower C_{d} than men in breaststroke

Sex difference in swimming performance decreased with increasing distance

The results of the present study showed a decrease in sex-related difference with increasing distance for both breaststroke and freestyle swimming. These results confirm the conclusions of Tanaka and Seals

Differences in upper body power might also play a role in the decreasing sex-related difference with increasing race distance

It has been assumed that women would be able to outrun men in ultra-marathon running and it was suggested that the sex difference in running would disappear with increasing running distance particularly in distances longer than the marathon

Limitations and implications for future research

This study has three major limitations. First, we investigated the ten fastest swimmers competing at national level and the eight finalists in the World Championships. The mean of eight swimmers might give a different result compared to the mean of ten swimmers. The 10^{th} fastest woman is not comparable, in terms of level and performance, to the 10^{th} fastest man; this might have influenced the sex difference. Future studies might also normalize the performance (

Conclusion

The results of the present study showed that swimming performance in athletes competing at national and international level improved in freestyle and breaststroke during the 1994–2011 period. The improvement might be related to technological advances, changes in anthropometric and physiological characteristics, improved training methods and competition psychology, improved sports nutrition, and/or increased access to the sport by a larger number of athletes. The sex-related difference in swimming performance did not change significantly over time in breaststroke, or in freestyle swimming by FINA competitors, but increased significantly in Swiss freestyle swimmers. Finally, the sex-related difference in performance declined with increasing race distance in both swim styles.

Competing interests

The authors declare that they have no competing interests.

Authors’ contributions

All authors have been involved in collecting data, writing, drafting and revising the manuscript. MW interpreted the data, drafted and revised the manuscript. CAR carried out the data collection, statistical analysis and interpretation. TR participated in its design and revised the manuscript critically for important intellectual content. RL participated in designing and coordinating the study and revised the manuscript critically. BK conceived, designed, coordinated the study and revised the manuscript. All authors read and approved the final manuscript.

Pre-publication history

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