Research Examines Elite Swim Times, Youth Sports Age Groups

An analysis by Indiana University researchers of top Olympic swim times since 1972 has found that a bias was introduced resulting in swim times in 2008 that were much faster than predicted.

Elite swimming is grappling with the issue of high-tech swimsuits, which many credit with an astounding number of world records set since the latest generation of suits was introduced in February 2008. The study does not identify what caused the bias but describes the statistical modeling that has successfully predicted swim times during the previous Olympics, aside from the Olympic Games in 1996, when times were slower than predicted.

The average error in predictions for 2008 Olympic swim times was three to six times greater than the errors in previous Olympics, said Joel Stager, professor in the Department of Kinesiology and director of the Counsilman Center for the Science of Swimming. Stager said the first step is to identify whether swim performances are being affected. The next step is a philosophical question that the greater swimming community needs to answer. No new advances in swimming techniques or training can account for the improved time, Stager said, so technology, such as swimsuits, or pharmacology could be responsible.

“Do we, as a community, want ‘assisted performance?'” he asked.

* Background: The fastest eight male and female performances in Olympic swimming events from 1972 through 2004 were analyzed. Using the mean time across all years, a best-fit power curve was calculated for each swim event. According to the study, these equations were used to predict the finish times for the 2008 Olympics. A binomial test of statistical significance was used to test whether the year as a whole was above or below the prediction line. In 2008, 65 percent of the Olympic swim events were faster than predicted. For the previous five Olympics combined, only 9 percent of the events were faster.

The study, “Identification of Bias in the Natural Progression of Swim Performance,” was presented during the Sport Science I Session of the annual meeting of the American College of Sports Medicine. Co-authors include lead author Christopher L. Brammer and David A. Tanner, both from IU’s Counsilman Center and Department of Kinesiology in the School of Health, Physical Education and Recreation.


Grouping youth athletes into multiyear age classifications is an attempt to level the competitive playing field and help athletes avoid injuries resulting from strength and size mismatches. Indiana University researchers say the current U.S. classification system for youth swimmers would be more effective if it stratified swimmers using a single age category, a common approach used in many other countries.

“Here, every two years you discourage a whole lot of kids,” said Joel Stager, professor in the Department of Kinesiology and director of the Counsilman Center for the Science of Swimming.

* Background: In the U.S., competitive youth swimming has four unisex age groups: 10 and under, 11- to 12-year-olds, 13- to 14-year-olds and 15-year-olds and older. Researchers examined the top swim times for these ages up to 21 years for the past three years in the 50-, 100- and 200-yard freestyle events. Significant differences in average times between all ages were found up to ages 13 and 14 for the girls, depending on the distance. For the boys, significant differences were found up to ages 15 and 16. Three homogeneous subsets were identified between the ages of 15 and 20 for women (15- to 16-year-olds, 16- to 18-year-olds and 17- to 20-year-olds). Three homogeneous subsets were found for men between the ages of 17 and 20 (17- to 18-year-olds, 18- to 19-year-olds and 19- to 20-year-olds).

Stager said researchers looked at various possible age groupings, and even grouping girls differently than boys, but decided a single-age classification would work best.

“There is no reason to suppose,” said Stager, “that this would not be true for other sports as well. Technological advances available today would make the sorting of times at swim meets and other athletic events easily manageable, as well.”

The study, “Age Classification in USA Swimming: Are Current Competitive Age Groups Appropriate?” was presented during the Sport Science I Session. Co-authors include lead author Kosuke Kojima and Christopher L. Brammer, also from the Department of Kinesiology in IU’s School of HPER.

Dozens of researchers from Indiana University participated in the annual meeting of the American College of Sports Medicine in Seattle May 27-30. To read about more IU research taken to the meeting, visit http://newsinfo.iu.edu/tips/page/normal/10999.html.

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