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Freestyle times (46.91 WR for 100m) tend to be faster than butterfly (49.82 WR for 100m) times. However, the "peak speed" for butterfly is faster than freestyle(1). Would this have to do with an aerodynamic or technical effect?

What are the technical differences between freestyle and butterfly?

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Without elaborating on the technical differences, because I'm probably not qualified to give a full answer in that respect, I'll answer the first part.

The reason butterfly has a higher peak speed is that you are pulling with both arms at once. When pulling with both arms, you're going faster than the one arm pull of freestyle. When recovering both arms, you are slower than the average freestyle speed in which you're pretty much always moving an arm or staying long in the water.

This pdf states:

The large power impulse generated by the simultaneous double-arm pulling pattern yields great propulsive potential; however, during the arm recovery phase there is no propulsion generated. This creates a minor ‘dead space’ in the stroke.

This ppt states:

...since speed drops significantly during the recovery phase, it is overall slightly slower than the freestyle.

I'm not entirely sure why the tradeoff ends up being slower. I know if you run into a wind for distance x and then with the wind for the same distance, it's slower than running with no wind, and that can be proven with simple math. Maybe that is the situation. You're pulling twice as hard and then getting no pull. And you can't be as long in the water all the time during butterfly, which is a big reason for speed. All the elite swimmers are pretty tall with large wingspans.

  • Any chance you're be interested in digging further into this when you get some time? Some references would be awesome to make this answer stand out even more – wax eagle Mar 27 '14 at 18:01
  • Yeah sure. I'll do a little research when I get off work. – Millie Smith Mar 27 '14 at 18:04
  • @waxeagle No time for research on the last paragraph or to add technical differences, but I'll try to do that this weekend. – Millie Smith Mar 28 '14 at 4:55
  • Good answer. I would suspect the tradeoff has to do with the variation of speed (perhaps butterfly undulates in terms of speed...and freestyle is more consistent). – user527 Mar 28 '14 at 13:21
  • Speaking from experience, one other limiting factor not mentioned here is that the fly technique is more physically intensive due to the shoulder strength/mobility to bring both arms over the surface simultaneously. It's a lot harder than the equivalent frontcrawl motion, therefore prone to cause greater overall fatigue. I don't have any scientific evidence to back this up though, aside from 25+ years of competitive swimming experience: ask any swimmer and they'll tell you fly is harder than frontcrawl. – Will Appleby Sep 26 '18 at 14:58

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