Does High Mileage Result in Faster Swims for Shorter Races? – by Dave Warden

I have some good news if you are a poor swimmer and do short distance triathlon. This news might shatter the psyche of those of you who have been swimming since you were in grade school. You’ll think me some sort of heretic for sharing this information. But, the legendary physiologist Dave Costill has undertaken a great deal of research on swim training over the last 30 years. In one study his team of scientists followed two groups of swimmers over a 25 week training period. Both groups began with once daily training, but one group moved to twice daily training in weeks 10 to 15, reverting to once daily for the rest of the study period. At no stage of the 25 week training period did this group show enhanced performance or increased aerobic capacity as a result of their extra training. Essentially, it was a waste of time.

In another study, Costill tracked the performance of competitive swimmers over a four-year period, comparing a group averaging 10 kilometers per day with a group averaging 5 kilometers per day. Okay, we need to pause right there. 10K of swimming a day!? In relation to changes in competitive performance time over 100, 200, 500 and 1600 yards improvements in swim times were identical for both groups at around 0.8% per year for all events. Again, even though one group did twice as much training, both groups benefited to the same extent in the long term. Holy cow! Costill went on to find that not only does super swim volume not help, but it can actually hurt you by programming too much of your muscle memory to slowtwitch muscles.

Now, I have a real-life experience that backs this up. I have a “friend” who is a bad swimmer. To protect this bad swimmer’s identity, let’s call him, oh, David. My friend David is decent on the bike and run, but I rarely crack the top 50% in swimming in races. I am, or he is, one of those triathletes who comes out of the water and starts to cry when he sees how few bikes are left on the racks. However, two times in the past 3 years David has done an Ironman, with an Olympic distance 5 weeks later. Both were the same races each year. In both Ironmen races, he was not even in the top 50% on the swim. However, in the Olympic distance race he was in the top 25% one year, and in the top 6% of the swim the next year. Top 6% in the swim? Man, David is a stud. So, how could he go from one of the worst to one of the best in just 5 weeks in both years? Now, the initial reaction you may have is that David is simply better at short distances than long, or that all his distance training for Ironman allowed him to perform better at the shorter distance. However, this is inconsistent with the other sprint and Olympic races that were done during the Ironman training, when volumes were high. In those short races during Ironman training with high swim volume, he still came in the bottom 50%, so it mitigates both of those arguments.

Because he was sick of swimming after the Ironman training, he cut his swim workouts to 3 a week, and the first year no more than 2000 meters a day, and for the second year, no more than 1500 meters a day for those 5 weeks. Those 1500-2000 meters a day were done almost exclusively at Olympic distance race pace. There were not even any drills. This is very similar to Costills findings. David simply dropped his volume and increased intensity.

Now, of course, this data and example would only apply to short distance racing. Costill’s data only measured up results of up to 1600 meter races. Obviously, for Ironman racing, you need to be pushing 4000 meters per workout, but for short distance racing, this has a huge impact on where you can consider spending your time when training.

Happy swimming!!

David Warden

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

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About The Author

Jen has been doing triathlon for several years. She is a former bobsled pilot for America Samoa and has a passion for the outdoors; especially winter mountaineering. At home she is wife to a mountain obsessed husband and mother of three girls, but here at EnduranceReview, she is an author, Managing Editor and token chick.