The 100m butterfly is over almost as soon as it starts, but it remains one of the most demanding sprints in the sport. Two lengths, one turn, and almost nowhere to hide if your technique breaks down. Unlike the 100m freestyle or backstroke, where a tiring stroke simply slows down, a tiring butterfly stroke collapses. The kick disconnects from the pull, the body flattens, and what was fast becomes a struggle in the space of a few strokes.
It is also one of the most exciting events to race well. A clean, fast 100m butterfly with a strong finish is one of the most satisfying swims in the sport, at any level.
Here is how to think about pacing and technique in the 100m butterfly, from your first competitive swim through to what Kristof Milak’s extraordinary comeback gold at Paris 2024 tells us about the event at the very top level.
What Makes the 100m Butterfly Different from the 200
If you have read our post on the 200m butterfly, the most important thing to understand about the 100m is that it requires the opposite mindset. In the 200, patience and conservation are everything. In the 100, controlled aggression from the start is the approach that works.
You do not have the luxury of four lengths to find your rhythm. You have two. Your start, your underwater, your first length, your turn, and your second length all need to be close to maximal effort, executed with enough technical control that your stroke holds together rather than collapses.
This makes the 100m butterfly a genuinely difficult balancing act. Go out too conservatively and you cannot make up the time on the way back, because butterfly does not allow the same kind of speed surge that freestyle does. Go out too aggressively and your stroke breaks down on the second length, costing you far more time than the extra effort gained you on the first.
For Younger and Beginner Swimmers: Technique Before Speed
As with the 200m butterfly, the single most important thing for a beginner butterfly swimmer to focus on before worrying about pacing is technique. Trying to swim the 100m butterfly fast with poor mechanics is exhausting and usually results in a swimmer who falls apart badly on the second length, sometimes resorting to a partial breaststroke kick or single-arm recovery just to finish.
The fundamentals worth getting right first:
Two kicks per cycle, properly timed: Your first kick should drive your hands forward into the water entry. Your second, slightly bigger kick should drive through your pull. If your kicks are not timed to your arm cycle, you are working against yourself rather than with the stroke.
A full body wave, not just arm movement: The undulation through your chest, hips, and legs is what makes butterfly efficient rather than exhausting. Swimmers who try to muscle through with just their arms tire extremely quickly. The wave motion, when timed correctly, uses far less energy than people assume.
A clean entry and a relaxed recovery: Your hands should enter the water in front of your shoulders, not crossing over or slapping down. Your arm recovery over the water should feel relaxed, almost lazy, saving your energy for the underwater pull where the real propulsion happens.
On pacing for younger swimmers: your first length should be strong but not maximal. If you are gasping for air at the turn, you went out too hard. The goal is to turn feeling like you have something in reserve for the second length, even if it does not feel like very much.
Stroke Count: Watching Your Technique Hold Together in Real Time
In a 100m butterfly, stroke count is one of the clearest signals of whether your race is going to plan. Elite 100m butterfly swimmers typically take between 17 and 20 strokes per 50 metres, with very little difference between their first and second length.
For club swimmers, here is a useful benchmark system for a 25 metre pool:
- Beginner age group: 22 to 28 strokes per 50m is common. Focus on the kick timing and body wave before worrying about reducing your count.
- Developing club swimmer: 19 to 23 strokes per 50m, with the goal of keeping your second length within two or three strokes of your first.
- Competitive club to national level: 17 to 21 strokes per 50m, with minimal variation between lengths.
If your stroke count on the second length is significantly higher than the first, your technique is breaking down under fatigue, usually starting with the kick. This is a clear training target. Specific underwater and stroke endurance work, discussed below, is what addresses it.
Breathing Pattern: A Tactical Decision Even in a Short Race
Even though the 100m butterfly is short, breathing pattern still matters tactically. Every breath in butterfly requires lifting the head, which briefly disrupts body position and adds drag. In a race decided by hundredths of a second at the elite level, breathing pattern can be the difference between a medal and missing the podium.
A common approach used by competitive swimmers:
- First 15 metres after the start: No breath, riding the speed from the dive and underwater dolphin kicks.
- Rest of the first 50m: Breathe every two strokes, keeping the stroke as clean and fast as possible.
- Second 50m: Most swimmers switch to breathing every stroke as oxygen demand increases, though some elite swimmers maintain every two strokes if their conditioning allows it.
There is no single correct pattern. It depends on your fitness, your stroke efficiency, and your specific race plan. What matters is that whatever pattern you choose, you have rehearsed it in training so it feels automatic under race pressure rather than something you are deciding on the fly.
The Underwater Off the Start and Turn: Critical in a Two-Length Race
With only one turn in the entire race, the underwater dolphin kick off the start and the single turn carry enormous weight in the 100m butterfly. Elite swimmers typically get 10 to 14 metres of underwater off the start and a similar distance off the turn, riding the momentum of the dive and push before their first stroke.
For age group and club swimmers, a strong underwater off both the start and the turn is one of the highest value technical skills you can develop for this event specifically. Every metre covered underwater is a metre covered without the energy cost of full butterfly stroke, which is the most energy-intensive stroke in the sport.
Pacing the 100m Butterfly: What the Data Shows
Across elite competitions, the 100m butterfly is consistently swum as a positive split, with the first 50m faster than the second. Most swimmers find their optimal split differential falls within a relatively narrow range, and larger variations typically indicate a pacing error or insufficient race-specific training rather than a deliberate strategy.
For club swimmers, here is a useful target framework:
- Beginner to age group: A 4 to 6 second differential between first and second 50m is typical. The goal over time is to close this gap through better technique and conditioning.
- Developing club swimmer: Aim to get your differential under 4 seconds.
- Competitive club to national level: A 2 to 3 second differential is the target, with elite international swimmers often achieving even tighter splits.
What Kristof Milak’s Paris 2024 Gold Tells Us
The men’s 100m butterfly final at Paris 2024 produced one of the most dramatic finishes of the entire Games, and it offers a genuinely fascinating case study in pacing and finishing strength.
Hungary’s Kristof Milak won gold in 49.90 seconds, but his path to that gold was anything but straightforward. He had a relatively slow start by his own standards, sitting in the middle of the field, and was reported to be only fifth at the halfway turn. From there, Milak produced the fastest closing 50 metres of the entire field to storm through and take gold by just 0.09 seconds over Canada’s Josh Liendo, who finished in 49.99 with a new Canadian national record. Ilya Kharun of Canada took bronze in 50.45.
What makes this race so instructive is the detailed technical analysis of what separated the medallists. Milak had the highest average distance per stroke of anyone in the field, meaning he was covering more distance per stroke cycle than his competitors even while accelerating through the final metres. Liendo, who led for most of the race, performed a fast open turn and underwater that put him in front, but his finish was slightly mistimed at the wall, which may have cost him the gold by the smallest of margins.
Ilya Kharun’s bronze medal swim is worth a specific mention for coaches and developing swimmers. He was the only swimmer in the field to increase his distance per stroke throughout the race, meaning his stroke actually became more efficient as the race progressed rather than less. That is an unusual and valuable trait, and it directly contributed to him moving from seventh place at the halfway mark all the way up to third by the finish.
The defending champion and world record holder Caeleb Dressel did not even make the final, finishing 13th in the semifinals after what was speculated to be the cumulative fatigue of multiple races on the same day. It is a reminder, even at the very highest level of the sport, that the 100m butterfly punishes anything less than precise execution and that reputation alone does not win races.
On the women’s side, the event was equally competitive, with several of the fastest swimmers in history converging on the Paris final. The performances reinforced a consistent theme across the men’s and women’s races: swimmers who maintained their stroke length and technical precision through the closing metres consistently outperformed swimmers who relied purely on speed in the opening 50.
How to Train for a Better 100m Butterfly
A few specific training approaches worth building into your programme:
- Underwater sets: 10 x pushoff and dolphin kick off both the start position and a simulated turn, targeting 10 to 14 metres on every rep. This is the single highest value technical skill for a two-length race.
- Stroke count sets: 6 x 50m butterfly on moderate rest, recording your stroke count on every rep. The goal is consistency between rep 1 and rep 6.
- Broken 100s: Swim 75m at race pace, rest 10 seconds, then race the final 25m. This isolates the most critical phase of the race, where most swimmers’ technique begins to break down.
- Distance per stroke drills: Swim 25m butterfly counting strokes, then try to repeat the same distance in fewer strokes without losing speed. This trains the kind of stroke efficiency that allowed Kharun to increase his distance per stroke under fatigue in Paris.
- Race simulation: Swim a full 100m butterfly in training at race effort regularly, not just in competition. The 100m butterfly is uniquely punishing, and rehearsing the specific feeling of the second length under fatigue builds the mental and physical tolerance needed to hold technique together on race day.
A Final Thought
The 100m butterfly rewards precision under pressure more than almost any other sprint event. There is very little room for error, and the margin between gold and missing the podium at the highest level is often a matter of hundredths of a second and a single well-timed finish.
For swimmers at every level, the lesson from Paris 2024 is the same one that defines great butterfly racing everywhere: technique that holds together under fatigue beats raw speed that does not.
At Vineyard Swimming we develop butterfly technique and race-specific pacing from the age group stage upwards in Cape Town. If you want to know more about how we approach the event, get in touch with Cape Town swim coach Duncan Bonney at Duncan@VineyardSwimming.co.za.
About Duncan Bonney
Duncan Bonney is an ASCA Level 4 and Swim SA Level 2 certified swim coach based in Cape Town, with over 10 years of experience coaching swimmers from beginner level through to SA Nationals. He manages Vineyard Swimming and has helped multiple athletes secure overseas university swimming scholarships. Read more about Duncan Bonney, connect on LinkedIn, or follow on X.