I bet that almost all of us have heard that drafting in the swim is a great way to either swim faster at your normal level of intensity, or maybe swim at the speed you would normally swim, but using less intensity. It’s well known that drafting on the bike makes a significant difference, as much as 20%. But drafting is illegal in most triathlons. However, drafting during the swim is legal. Now, I have heard commentary from triathletes that although swim drafting is legal, some question whether swim drafting is ethical. I won’t be digging into the ethics of swim drafting today, I’ll simply say I think it is ethical, primarily because in most mass swim starts, it’s simply unavoidable. What I do want to focus on is the scientifically proven performance gain from swim drafting, and I’ll do that with 3 specific studies.
The first is a 1998 study from the journal Medicine & Science in Sports & Exercise. This study took 8 triathletes, not swimmers but triathletes, in a controlled environment and concluded that they were able to swim 3.2% faster when drafting then when not drafting. 3.2% is pretty significant, about 40 seconds over a mile swim. What was also interesting is that they looked at skin fold thickness, and concluded that drafting benefited leaner swimmers, but that this benefit did not reveal itself in non-drafting positions. I conclude from this that swimmers who are not as lean, expose more of their profile outside the drafting zone, whereas lean swimmers can hide more effectively in the shadow of the swimmer they are drafting from. A 2003 study from this same journal concluded that swimmers were 4.8% more efficient after drafting for 750 meters vs. swimming 750 meters solo.
I told you there was a 3rd study, and this one is the most fascinating to me. But before I talk about this one, let’s discuss drafting position. Most of the drafting material I have read says to draft behind and laterally of the lead swimmer. Meaning, draft on the side, in what would be their “blind spot” if you were automobiles instead of swimmers. But, this 3rd study disputes that. This 2003 study, also from the journal Medicine & Science in Sports & Exercise found that drafting 0-50cm directly behind the lead swimmer resulted in a 21% reduction in drag at 0cm behind the lead swimmers toes, and a 20% reduction in drag 50cm behind the lead swimmers toes. Now, that’s not a 20% gain in speed that is a 20% reduction in drag. The researchers did not make a conclusion on performance gains, just the effect of drag. But we all know that swimming is almost exclusively a fight against drag, and 20% is no small benefit. What I found encouraging about this, was that you didn’t have to be scrapping the lead swimmers toes to gain the advantage. 50cm is almost 20 inches, which is a nice and polite distance to swim behind your host. Now, these researchers also looked at rear/ lateral drafting, so not side to side, but somewhat behind and to the side of the lead swimmer. The maximum drag reduction in rear/lateral drafting was only 7%, which still isn’t’ bad, but it’s only 1/3 of the drag reduction from being directly behind the swimmer.
In summary, is swim drafting worth it? This question reminds me of the article when I covered transitions. It is all a matter of return on investment. If practicing drafting with your swim buddies for a few hours will result in a 3% increase in swim performance, then the answer is absolutely yes, it is worth it. However, I see two risks. I fear the risk of latching myself onto a swimmer in a race who is either a) slower than me, and I won’t know that until I get to T1, or b) a swimmer who goes off course and ends up zig-zagging all over the lake. If you can trust your lead swimmer’s navigation, and are confident that they are slightly faster than you, I say draft away.
David Warden is a 3-time USAT All American and Elite Coach with Joe Friel's TrainingBible coaching. His work has been published in Triathlete and USA Triathlon Life magazines. He is the former Vice-Chair of the USAT Rocky Mountain Region, and the host and producer of the #1 triathlon podcast, Tri Talk and part owner of www.powertri.com.