What Is the Butterfly Stroke?

Butterfly is a constructed competitive stroke featuring simultaneous arm pulls over the water, a dolphin (two-legs-together) kick, and rhythmic body undulation. It was recognized as the fourth official competitive stroke in 1952 and is governed today by World Aquatics.

The butterfly stroke stands as the most explosive, powerful, and visually striking of all swimming strokes. Unlike freestyle, backstroke, and breaststroke—which evolved naturally from human movement—butterfly is an entirely constructed technique born from competitive swimming's constant drive to go faster.

Butterfly emerged in the 1930s as swimmers discovered that a simultaneous, synchronized arm recovery over the water—combined with an undulating body motion—allowed them to overcome the resistance of breaststroke. Initially called the "butterfly breaststroke," it was so revolutionary that by 1952, competitive swimming recognized it as a distinct fourth stroke. According to World Aquatics (the international governing body for aquatic sports), butterfly is now swum at every major competition from age-group nationals to the Olympic Games.

Why is butterfly so demanding? Because it requires perfect synchronization. Your arms must move simultaneously. Your legs must move simultaneously. And everything must coordinate with your breathing and body undulation in precise rhythm. A single mis-timed kick or arm entry throws off your entire stroke and kills your speed.

The good news: butterfly is absolutely achievable for swimmers of all levels. Yes, it takes practice and patience. But with proper instruction, consistent drills, and intelligent training, any swimmer can master this beautiful, powerful stroke.

How Does Body Position and Undulation Power Butterfly?

Butterfly power comes from a continuous body wave: chest press down, hip drive up, once per arm cycle. Your head stays neutral (eyes down), hips stay near the surface, and the undulation should look smooth and shallow — never porpoising.

Before your arms or legs move, your body must undulate. This undulation—a rhythmic, wave-like motion through your core—is the engine that powers butterfly. Without proper body position and undulation, your arms and legs are working against the water instead of with it.

The Neutral Position: Start by lying horizontal in the water on your front. Your head is neutral (eyes looking down at the pool bottom), with the back of your head at the water surface. Your hips are at or slightly above the water surface. This is your baseline—the position you'll return to repeatedly throughout the stroke cycle.

The Chest Press: As your arms enter the water in front of you, your chest presses downward and forward. This is not a violent action; it's a smooth, controlled depression of your chest that creates a wave of momentum through your body. Think of it as your chest "sinking" slightly into the water to initiate the undulation. This chest press happens as your arms begin their pull.

The Hip Drive: As your arms pull and push through the middle of the stroke, your hips rise. This is a natural consequence of the wave traveling down your body—your chest sinks, the wave travels to your core, and your hips follow upward. This hip drive is critical: it's where most of your power comes from. USA Swimming research shows that swimmers with strong hip drive produce significantly more propulsive force than those who rely solely on arm strength.

The Body Wave in Action: The entire undulation sequence looks like a wave rippling through water. Your head starts neutral, your chest presses down, the wave travels through your torso, your hips rise, and then everything returns to neutral. This isn't a jerky, exaggerated motion—elite butterfly swimmers undulate with smooth, continuous flow. The wave happens once per arm cycle (not once per leg kick).

To practice body position and undulation on land: Lie on your stomach and arch your chest slightly, then press it back down. Feel that wave? That's the undulation. In the water, you'll add gentle leg movements to propel this wave, and your arms will guide it.

How Do You Perform the Dolphin Kick Correctly?

The dolphin kick originates from your hips (not your knees) and travels as a whip-like wave through relaxed knees and flexible, pointed ankles. Butterfly requires exactly two dolphin kicks per arm cycle — one on entry, one on push.

The dolphin kick is unlike any other swimming motion. Both of your legs move together, simultaneously, creating a powerful, whip-like motion that originates from your core and flows all the way to your toes.

Initiation from the Hips: The dolphin kick is not a knee-kick. It doesn't originate from your knees bending and straightening. Instead, it originates from your hips. Your hips flex downward, and this movement propagates through your thighs, knees, and ankles in a smooth, continuous wave. Your knees should stay relatively relaxed and straight; they bend naturally as a result of hip and ankle motion, not as an isolated movement.

Ankle Flexibility Is Critical: Your ankles must be flexible and plantarflexed (pointed). Many swimmers struggle with dolphin kick because they have stiff ankles. As your legs whip downward and then upward, your feet should flex at the ankles, creating maximum surface area to push against the water. If your ankles are stiff, you'll create drag instead of propulsion. Stretching your ankles daily—pointing and flexing your feet, rotating them—is essential for butterfly swimmers.

Two Kicks Per Arm Cycle: In butterfly, you take exactly two dolphin kicks per complete arm cycle. The first kick happens as your arms enter the water (this is sometimes called the "catch kick"). The second kick happens as your arms exit and recover over the water (the "push kick"). This 2:1 rhythm is fundamental to butterfly timing.

Depth and Power: Your dolphin kick should create a visible wave at the water surface but shouldn't break the water or create a huge splash. The kick should be powerful enough to provide propulsion (your feet should move roughly 2–3 feet down and up from your neutral position) but controlled enough to maintain rhythm. Younger or less flexible swimmers may have a shallower kick; that's fine. As you develop ankle flexibility and hip strength, your kick will deepen naturally.

Practice the dolphin kick on a kickboard (holding it vertically or horizontally), on your back, or with a flutter-kick tool. Isolating the kick helps you perfect the motion before synchronizing it with your arms.

How Does the Butterfly Arm Stroke Work?

Both arms enter the water simultaneously at shoulder width, catch with high elbows, pull inward in a keyhole shape, push backward with acceleration, and exit thumbs-first before recovering over the water. The high-elbow catch is where the power lives.

The butterfly arm stroke is often described as a "keyhole pull" because of the shape the hands trace underwater. Understanding this path—entry, catch, pull, push, and recovery—is essential for generating power and speed.

Entry: Both arms enter the water simultaneously, roughly shoulder-width apart (or slightly wider), in front of your head. Your arms are extended but not locked; there's a slight bend at the elbow. Your hands enter first, fingertips leading, with palms angled slightly outward and downward. This entry happens at the same moment as your first dolphin kick (the catch kick).

Catch: Immediately upon entry, your hands "catch" the water. This means you position your forearm and hand to apply force. Your elbows flex slightly, and your hands begin to angle inward. You're not pushing yet; you're establishing connection with the water. Elite swimmers spend only 0.2–0.3 seconds in the catch phase.

Pull: Your hands and forearms pull the water backward and slightly inward, moving in a sweeping arc. At this phase, your elbows stay high—never dropping below your hands. This high-elbow position is crucial: it allows you to apply force through the full length of your forearm and hand, not just your hand. Your hands move inward in an "I" shape (not widely swept out). By the midpoint of the pull, your hands are roughly aligned under your shoulders.

Push: As your hands reach the midpoint under your body, they transition from pull to push. Your hands continue moving backward and slightly outward, propelling water behind you. This is where maximum power is applied. Your hands accelerate during the push phase. This phase coincides with your second dolphin kick (the push kick), which is why coordination is so important—the kick adds momentum exactly when your arms are most powerful.

Exit and Recovery: As your hands exit the water at your hips, your thumbs leave first (this helps with a clean exit). Your arms immediately begin their over-water recovery: elbows lead, arms swing forward in a wide arc, and your hands re-enter in front of your head. This recovery happens quickly and forcefully—it's part of the momentum that carries you through the next stroke. Some swimmers describe the recovery as "whipping" the arms forward; that's an apt description.

The entire arm cycle takes roughly 0.8–1.2 seconds depending on stroke rate. Faster swimmers spend less time in the water (quicker pull and push) and make up time with a faster stroke rate and stroke length.

How Should You Breathe During Butterfly?

Breathe forward, not upward — let your body undulation naturally lift your chin above the water and inhale quickly through your mouth. Your forehead stays low and your eyes look down; lifting your head forward drops your hips and destroys streamline.

Breathing in butterfly is different from other strokes because your head must travel upward as your body undulates—but your breathing mechanics are forward, not upward.

Forward Breathing: As your arms pull and push, your body naturally begins to rise. Your chest presses down initially, then rises as your hips drive upward (remember the undulation?). As your body rises, your chin naturally comes above the water surface. This is where you breathe: when your chin clears the water, not by lifting your head up. Your forehead stays low; your chin comes forward and up over the water's surface. You should see water at your hairline when breathing, not clear air above your eyes.

When to Breathe: There are two common patterns: breathing every stroke (every arm cycle) or breathing every other stroke (every two arm cycles). Sprinters typically breathe every stroke to maintain oxygen supply during maximal effort. Distance swimmers and those building endurance may breathe every other stroke to develop breathing control and streamline.

For beginners, breathing every stroke is recommended. This takes the stress of breath-holding out of the equation and lets you focus on technique. As you develop fitness and comfort with the stroke, experiment with every-other-stroke breathing.

Timing the Breath: Inhale as your body rises (usually during the middle of your arm pull and push). Exhale as your face returns to the water and your body undulates back down. Some swimmers exhale through both nose and mouth; others use mouth only. Nasal exhalation can help water from entering your nose, but it's not essential. Experiment and find what works for you.

Head Position: Keep your head as neutral as possible. Don't look forward; look down. Your eyes should track the bottom of the pool or the lane line below you. This neutral head position reduces drag and helps maintain body alignment. Lifting your head forward (rather than allowing it to rise with your body) will drop your hips and kill your speed.

What Is the Correct Timing and Coordination for Butterfly?

Two kicks per arm cycle — kick one on entry, kick two on the push. Body undulation happens once per cycle, and breathing (when used) falls naturally as your body rises on the push phase. When timing is right, butterfly feels smooth; when it's off, it feels like thrashing.

Butterfly's greatest challenge is coordination. Your arms, legs, body, and breathing must all work in precise synchrony. A mistake in any one component throws off the entire stroke.

The Two-Kick Cycle: Remember: two kicks per arm cycle. Kick #1 happens as your arms enter the water (the catch phase). Kick #2 happens as your arms exit and begin recovery (the push phase). This rhythm is non-negotiable. If you kick three times per cycle, your timing is off. If you kick once, you're not producing enough propulsion.

To internalize this rhythm, count aloud: "One-two, one-two" as you swim. Kick on "one" (entry), kick on "two" (exit). Many coaches teach this count to swimmers.

Body Undulation Timing: Your body undulates once per arm cycle, in sync with the two-kick sequence. As your arms enter, your chest presses down (first kick). As your arms pull and push through, your hips rise (second kick). By the time your arms exit and begin recovery, your body is returning to neutral, ready for the next cycle.

Breathing Coordination: If breathing every stroke, your inhale happens as your body naturally rises (around kick #2, the push phase). Your exhale happens as your face returns to the water and your body resets. The body undulation and breathing timing should feel natural; you're not forcing your head up—you're breathing as your body rises.

Smooth vs. Choppy: When your timing is perfect, butterfly feels almost effortless—smooth, flowing, continuous. When timing is off, the stroke feels choppy and exhausting. If you feel like you're fighting the water, check your timing first.

How Do You Execute Butterfly Starts and Turns?

Starts use a forward dive followed by powerful underwater dolphin kicks (up to 15 meters per World Aquatics rules). Turns require a simultaneous two-hand touch, an explosive push-off, and more underwater dolphin kicks before surfacing — these underwater phases are often the fastest part of the race.

In competition, how you start and turn can determine race outcomes. Butterfly starts and turns have specific technical requirements.

Dive Start: The butterfly dive start is similar to freestyle and breaststroke, but with one key difference: after you enter the water, you perform underwater dolphin kicks (not flutter kicks or breaststroke undulation) to maintain momentum. According to USA Swimming guidelines, you're allowed up to one full stroke underwater before breaking the surface (so approximately 2–3 dolphin kicks depending on your length). These underwater dolphin kicks should be powerful and fluid, building speed before you surface and begin stroking.

Push Start (if applicable): In age-group or recreational settings, some programs allow swimmers to push off the wall rather than dive. The same principle applies: powerful underwater dolphin kicks immediately after pushing off.

Two-Hand Touch Turn: At the wall, butterfly requires that you touch with both hands simultaneously. This is one of the most important rule distinctions (unlike freestyle, where you can touch with one hand). Approach the wall with two powerful strokes, and on your final stroke, as your arms exit and begin recovery, let them extend forward to touch the wall with both hands at the same time.

Once you've touched, perform an explosive push-off from the wall, and immediately begin underwater dolphin kicks (up to one full stroke's worth) before surfacing and resuming butterfly. The turn is not just a touch-and-go; it's an opportunity to gain speed advantage.

What Are the Most Common Butterfly Mistakes and How Do You Fix Them?

The most common butterfly errors are over-undulating (porpoising), alternating-leg kicking, breathing too late, dropping elbows, and asymmetrical arms. Each is a timing or body-awareness issue, correctable with targeted drills and video feedback.

Even experienced swimmers make butterfly mistakes. Here are the most common ones and how to correct them:

1. Over-Undulating (The "Porpoise" Kick): Some swimmers exaggerate their body wave, creating a huge undulation that looks like a dolphin breaching. This kills speed and wastes energy. The undulation should be subtle and continuous, not exaggerated. Fix: Practice dolphin kick on your side, where you can see the motion without the full body position confusing you.

2. Single-Leg or Alternating Leg Kick: Beginners sometimes slip into flutter-kick or alternating-leg patterns. This happens because flutter kick feels natural from freestyle. Butterfly requires simultaneous kicks. Fix: Do vertical kicking drills (holding the side of the pool, kicking vertically) to enforce the simultaneous motion.

3. Breathing Too Late: If you wait until your arms are fully exiting the water to breathe, you've missed your window. Your body rises as your arms pull/push, not after. Breathing too late forces your head up, drops your hips, and breaks your body line. Fix: Practice breathing on every stroke until the timing is automatic.

4. Dropped Elbows During Pull: Dropping your elbows below your hands wastes force. Your forearm and hand should remain the propulsive surfaces throughout the pull. Fix: Practice single-arm drills and focus on keeping your elbow high and in front of your hand.

5. Straight Arms During Entry and Catch: If your arms are completely straight as they enter, you've missed the early catch phase. There should be a slight bend at the elbow to set up the pull. Fix: Video yourself or have a coach watch; focus on a small elbow bend at entry.

6. Asymmetrical Arms (One Arm Leading): If one arm consistently enters the water before the other, your stroke is asymmetrical, which kills efficiency. This is often caused by core weakness or bilateral imbalance. Fix: Strengthen your core with planks and rotational exercises. Use single-arm drills with focus on matching timing.

7. Holding Your Breath: Holding your breath creates tension and throws off your timing. You should exhale continuously into the water and inhale only when your mouth is above the surface. Fix: Practice relaxation drills and rhythmic breathing patterns.

What Drills Help Improve Butterfly at Every Level?

Beginners benefit most from dolphin kick on a kickboard and vertical kicking. Intermediate swimmers use single-arm butterfly, catch-up, and 3-3-3 drills. Advanced swimmers refine with fingertip drag, kick-switch, and every-other-stroke breathing work.

Drills isolate specific components of the stroke so you can practice them in a focused, low-pressure way. Here are essential drills for all levels:

1. Dolphin Kick on Kickboard: Hold a kickboard horizontally in front of you and kick. This isolates the leg motion and lets you focus on hip initiation, ankle flexibility, and the 2:1 rhythm.

2. Vertical Kicking: Hold onto the side of the pool (or have a partner hold you) and kick vertically. Your head stays above water. This reinforces simultaneous leg motion and builds hip and ankle strength.

3. Single-Arm Fly: Swim butterfly with one arm pulling while the other stays extended in front or at your side. Your legs do the full dolphin kick. This drill develops feel for the arm pull, breath timing, and body rotation independent of arm symmetry.

4. The 3-3-3 Drill: Swim 3 strokes of butterfly, then 3 kicks on a kickboard, then 3 more strokes. This reinforces the connection between kick timing and arm timing while breaking the stroke into manageable chunks.

5. Catch-Up Drill: Swim butterfly while trying to let your hands "catch up" to your head before entering. This emphasizes a patient, controlled entry and prevents rushing the stroke.

6. Fingertip Drag (Recovery Drill): During the over-water recovery, let your fingertips barely drag the water surface. This keeps your recovery high and controlled and prevents "slapping" the water on entry.

7. Kick-Switch Drill: Kick on your side (with one arm extended forward, one at your side) for several kicks, then switch sides. This develops dolphin kick feel and body rotation awareness.

8. Breathing Every Other Stroke: Once comfortable with every-stroke breathing, practice breathing every other stroke. Swim several lengths, breathing on every second arm cycle. This builds breath-hold tolerance and develops stroke consistency.

Incorporate 2–3 drills into every butterfly session. Spend 5–10 minutes on drills before moving to full-stroke swimming.

How Do You Build Butterfly Endurance and Speed?

Start with short repeats (50–75m) and add 25m per week. Mix aerobic pace with anaerobic descending sets, supplement with core/shoulder/ankle strength and mobility, and treat recovery as non-negotiable. Smooth beats choppy at every speed.

Butterfly is exhausting. Unlike freestyle, which you can swim for long distances at comfortable pace, butterfly requires significant energy. Here's how to build butterfly capacity:

Start Short, Build Long: Don't expect to swim 200m butterfly your first week. Start with 50m or 75m repeats with rest, and gradually increase distance. Add 25m per week (or every other week) as your fitness improves. In 8–12 weeks, you'll be ready for sustained 200m efforts.

Descend Sets: A descend set means each repeat gets progressively faster. For example: 4 x 50m butterfly (swim each 50 faster than the last). This teaches your body to increase tempo while maintaining technique. By the time you hit your fastest repeat, your stroke should still feel controlled.

Aerobic vs. Anaerobic: Not all butterfly training should be all-out effort. Mix aerobic pace (sustainable, conversational effort) with anaerobic work (hard, breathless efforts). A sample session might be: 5 x 100m butterfly at steady aerobic pace with 20 seconds rest, then 5 x 50m at harder pace with 30 seconds rest. This develops both endurance and speed.

Avoid Gassing Out: If you consistently run out of air or feel completely exhausted mid-swim, you're either going too hard too soon or your technique is inefficient. Slow down. Focus on smooth, controlled strokes. Butterfly isn't about thrashing; it's about power and efficiency. A slower, smoother stroke is faster than a faster, choppy one.

Cross-Training: Butterfly takes a toll on your shoulders and core. Include freestyle, backstroke, and breaststroke in your training to develop balanced fitness and give butterfly muscles a break while maintaining aerobic fitness.

Strength and Conditioning: Land-based training is essential. Focus on:

  • Core work: Planks, dead bugs, bird dogs, rotations. A strong core powers undulation.
  • Shoulder strength: Push-ups, pull-ups, resistance band work. Strong shoulders drive arm power.
  • Hip flexibility and strength: Hip openers, lunges, clams, bridges. Hip mobility is essential for dolphin kick.
  • Ankle mobility: Daily ankle stretches and rotations. Flexible ankles are non-negotiable for butterfly.

Spend 15–20 minutes, 2–3 times per week, on land training.

Recovery and Injury Prevention: Butterfly is demanding on shoulders, hips, and knees. Listen to your body. If you experience pain (not just fatigue), take a break or switch to other strokes. Recovery days matter. Foam rolling, stretching, and adequate sleep are not optional.

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Frequently Asked Questions About Butterfly

Q: How long does it take to learn butterfly?
A: With 2–3 lessons per week, most swimmers develop a functional butterfly stroke in 4–8 weeks. Mastering it (racing confidently and efficiently) takes several months to a year of consistent training. The timeline depends on your prior swimming experience and natural aptitude.

Q: Is butterfly harder than other strokes?
A: Yes, butterfly is the most demanding stroke physically and technically. It requires perfect synchronization, explosive power, and significant cardiovascular effort. But "harder" doesn't mean "impossible." Every Olympic butterfly swimmer started exactly where you are.

Q: What's the difference between fly and butterfly?
A: No difference. "Fly" and "butterfly" are the same stroke. "Fly" is short-hand used in casual conversation and training (e.g., "swim some fly"). "Butterfly" is the official name.

Q: Can I breathe every stroke in butterfly?
A: Yes. In fact, for beginners and when building endurance, breathing every stroke is recommended. It allows you to focus on technique without the added stress of breath-holding. As you improve, you can transition to every-other-stroke breathing.

Q: What's the fastest way to improve butterfly?
A: Consistent drills, video feedback, and quality coaching are the fastest route. Working with a coach who can identify specific technique issues and give you targeted drills will accelerate improvement far more than solo training.

Q: Does my ankle flexibility really matter that much?
A: Absolutely. Stiff ankles severely limit your dolphin kick efficiency. If you have tight ankles, spend 5–10 minutes daily on ankle flexibility work. This is one area where consistent, small efforts pay huge dividends.