Most swimmers do not lose their butterfly on the arms or the kick. They lose it on the breath. The air goes in a fraction too early, the chest climbs, the hips drop, and the next cycle starts with the body pointing uphill. From the deck that looks like fatigue. It is usually timing.
Butterfly is the second leg of the 200 individual medley, the event I swam at two Olympic Games for Brazil and won at the 2015 Pan American Games in Toronto in 1:57.06. There the fly has to be fast and cheap at once, and the breath is where the cost hides.
What is the right breathing timing in butterfly?
Late in the underwater pull, and finished before the hands come forward over the water. A 2025 study in Frontiers in Sports and Active Living describes the frontal breathing action in butterfly as happening "during the late half of underwater arm stroke to inhale", in its work on muscle activity and coordination with and without the breathing action. That is the window. Not at the entry, not while the hands are still out front catching water, but in the back half of the stroke, when the hands press toward the hips and the shoulders come up on their own.
The US Masters Swimming guide to butterfly body position says the same from the swimmer's side of it. It tells you that "Your shoulders begin to rise as you start to pull, so timing your breath with the beginning of your pull is important", and sets a blunt checkpoint: "By the time you finish your pull, your head should be up and you should be breathing."
So the pull is what lifts you. You take the air it has already given you, breathing "with the rising of your shoulders, which allows your chin to clear the surface". If you have to lift to find air, you took it too early.
Why does lifting the head to breathe cost so much?
Because it tilts the whole body, and a tilted body plows. The Frontiers paper explains that in frontal breathing swimmers "lift their head, shoulders, and trunk toward the surface" to inhale, and that "This action causes an increase in the angle of body inclination", which it gives as a reason breathing can hurt performance. It puts no number of seconds on that cost, and the mechanism is the useful part anyway: the more trunk you lift and the longer you leave it up, the more of the cycle you spend pushing water instead of slipping through it. You are not trying to avoid breathing. You are trying to keep the lift small and short.
The chin matters more than the mouth. The guide asks you to "Keep your chin as low to the water as possible while still ensuring you're taking in air and not water". Push it forward along the surface, not up off it.
Should my head be down before my hands enter?
Yes, and this one correction fixes more butterfly than any other. The masters guide is direct about the urgency: "Once you get your breath, it's a race to get your head back down before your arms enter the water." Its finish line is just as clear: "By the time you finish your recovery, your head should be in line with the rest of your body."
If the head is still up when the hands land, the entry happens with your shoulders high and your hips low, and the second kick has nothing clean to drive into. That is where the sinking feeling at the front of the stroke comes from. I covered how the two kicks sit in one arm cycle in the butterfly hub, and this rule keeps that rhythm alive.
How often should I breathe in butterfly?
Less settled than anyone admits, and the research I can open does not hand you a rule. The Frontiers study compared "swimming with the frontal breathing action for every stroke" against a task alternating breathing cycles with breath-holding cycles, in a group it describes this way: "Eight national-level female swimmers participated in this study." Its finding on speed was that "the different breathing frequencies with breath-holding did not affect the butterfly swimming speed."
The authors flag "the small sample size", and state that "the results of this study are only considered applicable to frontal breathing action and sprint pace". Eight swimmers sprinting is a hint, not a law.
What changed matters more. The paper reports that "the arm and leg phase structure changed in the breath-holding cycle", and that "The push phase in the BH cycle was longer than those in the BE and BABH cycles", BH being the cycle where they held the breath. A breath-holding cycle is a different stroke, not the same one with the air removed, which is why training only breath-holding fly leaves your racing stroke untouched.
My position, as a coach rather than a citation: learn the stroke breathing every second cycle, because that rhythm forces the head down fast, then build the version you will race. What you are buying is a breath cheap enough that taking it every cycle does not break the wave. In the 200 IM I would never trade a clean body line for one saved breath.
How does SwimRead read this part of your swimming?
It does not read butterfly yet, and you should know that before you film. The SwimRead home page states that "The current beta supports freestyle filmed from the side of the pool," and that "Backstroke, breaststroke, butterfly, underwater footage, starts, and turns are not supported analysis modes in this beta."
What it does today is read a short freestyle clip. The page asks you to "Aim for 10 seconds of continuous freestyle," filmed "in landscape from the side, with the whole body visible, a stable camera, standard lens, and normal playback speed," and from that "On-device pose detection estimates up to 33 body landmarks in sampled video frames." It stops short of a verdict, since "These estimates are not validated technique grades."
On butterfly you are still your own analyst, and this fault is visible to the naked eye. Phone on the deck in landscape, film from the side, and judge one frame: where your hands touch the water. If the freestyle version is yours too, the app reads that, and I covered it in freestyle head position.
What should you drill this week?
- One arm butterfly, breathing to the front. The breath has to fit inside a single pull, which forces it late.
- Three strokes, one breath, over 25m. Not for fitness. It isolates the head-down timing so you feel what the breathing cycle should look like.
- Freeze frame checks. Film one 25m from the side weekly and pause at hand entry. Face down and in line, or late.
- Chin on the surface. Swim 25m taking the air with the chin skimming the water, even if you get a mouthful. You are calibrating the minimum lift.
- Butterfly kick on your back. It removes the breath entirely and shows whether the wave starts at your chest or your knees, the check I use in the underwater dolphin kick work.
Time those 25s in my free swim pace calculator to see whether the cheaper breath came out faster rather than just feeling tidier. If the stroke is clean and you still lose the race at the walls, the open turn for butterfly and breaststroke is the next piece.
SwimRead is free while in beta, and paid plans will come later with beta testers told before anything changes. For a reading of your freestyle, join the beta and leave your email for an invitation as beta spots open.