Is the wetsuit effect for real?

A few months ago, my niece called me and asked me to help her devise a science fair project. Research is my thing, but I am not very well versed in the nuances of 8th grade assignments. I asked Dr. Google for some ideas, but nothing seemed original or interesting, and if I wasn’t interested, there is no way my 14 year old niece would be interested. Then, in a flash of shear genius (if I don’t pat myself on the back, nobody will) I had an idea. How about formally testing the wetsuit effect?  You know, the notion that non-swimmers benefit more from a wetsuit than swimmers.

My niece is a swimmer, so she immediately embraced the proposal. The final plan was to get about 20 masters swimmers of varying abilities and have them swim 200 yards with a wetsuit and without a wetsuit. Her hypothesis was the faster swimmers would have less of a time difference than the less fast swimmers (how PC is that? I didn’t call them “slower” swimmers).

Now, all of you are saying to yourselves, “Duh. We all already know that faster swimmers have less advantage than slower swimmers when wearing a wetsuit.” Only one has examined this issue and it was way back in 1996. The subjects were 18-20 years old, so they were much younger than the typical triathlete. This was an opportunity to get a concrete time difference in older triathletes and master’s swimmers.

Given that this is an 8th grade project, the methodology and execution of this little experiment are basic, so no grousing about the crude nature of this investigation. There was no controlling for the type of wetsuit, how often a person had worn a wetsuit previously, the temperature of the water, and many other variables. However, I think the results are still interesting, and I would venture to guess that a larger, more advanced study would yield very similar findings.

Twenty-one suckers, I mean people, agreed to participate in the study.  The average age of the swimmers was 47. There were 6 females and 15 males. Participants were randomly assigned to wearing the wetsuit first or second. The average swim time without a wetsuit was 2:34.6 and with a wetsuit was 2:25.9, meaning for the entire sample, there was about a 9 second improvement over 200 yards when wearing a wetsuit.

The results that were the most applicable to triathletes were when the participants were divided into sub-groups depending on when they started swimming. Ten of the participants started swimming as adults; the remaining 11 began swimming as children. The participants who started swimming as adults swam an average of 2:54.9 without a wetsuit and 2:40.9 with a wetsuit. That is a whopping 14 second improvement over 200 yards! The participants who started swimming as children swam an average of 2:16.1 without a wetsuit and 2:12.3 with a wetsuit, a meager 3.8 second improvement. As you can see, the group that started swimming as adults was slower overall on both the wetsuit and non-wetsuit trials by a large margin.

Being the extreme statistical nerd that I am, I did a t-test on these data and even with 21 subjects the results were statistically significant at the p<0.01 level. Just for more kicks, I did a regression analysis which was also significant. Don’t worry, the extra analyses were for my own interest and are not part of the science fair.

What does this mean in practical terms, aside from the fact that if you started swimming as an adult you are basically screwed? Here’s a cute little table that explains it all.

This table represents the most conservative estimates of swim improvement for the “non-swimmers”. I think the improvement will actually be more the longer the distances due to cumulative fatigue and the increased reliance on the wetsuit for buoyancy, a condition that is not as pronounced in the swimmers.

The bottom line: the wetsuit effect is real.

Editor's Note: Joanna Zeiger is a scientist, triathlon coach, and a world-class professional triathlete. You can read more of her hard-earned advice on most excellent blog Fast at Forty.

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Photo Credit: http://grantandamycropper.blogspot.com