There were an impressive number of record-breaking performances at the London Olympic Games, but researchers say that was something of an anomaly.
Using a specially-designed model that indicates performance predictions, a team at the Counsilman Center, Indiana University, Bloomington, has accurately predicted 87 percent of all Olympic events between 1988 and 2004. But this year, only 31 percent of the men’s events and 38 percent of the women’s events were successfully predicted.
Results are similar to 2008, when only 34 percent of the Olympic swimming performances were accurately predicted using the same model.
“We concluded that the  Games were significantly biased, likely due to the introduction of ‘new-tech” body suits,’” said Chris Brammer a lead researcher.
Earlier variances were caused by other irregularities such as documented steroid use in 1976, and the Olympic Boycott of 1980, and given that FINA banned the 2008 suits in 2010 — thus removing the bias — Brammer and the team had expected to see a return to the earlier percentages in 2012.
“The past two Olympics, 2008 and 2012, have acted to shift the global performance curve toward faster rates of improvement,” said Brammer. “However, the improvement in performance seen in 2008 was much larger than in 2012, suggesting a slowing in performance progression. This fact suggests: Either performances are returning to the expected performance curve, or the performance curve has shifted and competitors are again approaching the limits to swim performance.”
Ultimately, the causes of the biased performances will need further study he added.
Brammer’s colleagues include Joel Stager, Dave Tanner and Kirk Grand.