Butterfly Stroke Technique: How to Swim Dolphin Kick

Butterfly is the stroke nearly every endurance athlete skips — and the one that gives them the most. Not as a race stroke, but as a technique tool: butterfly is the most honest test of torso control, rhythm and feel for the water. Anyone who owns the body wave also swims freestyle more economically, because the connection between hips, torso and kick improves. This article breaks the stroke into its four components, gives the concrete timing values, lays out a six-week build-up without frustration, and explains how much butterfly actually belongs in triathlon training.

Why butterfly is the most expensive stroke

Butterfly costs roughly 20 to 30 percent more energy than freestyle at the same speed. Two reasons: first, there is no alternating movement — both arms work at once, so there is no phase in which one arm relaxes and glides forward. Second, the recovery over water: arms and shoulders are carried forward against gravity, which demands an active force impulse in every cycle. On top of that comes the enormous drag when the hips sink while the arms swing back to the front.

That is exactly why the stroke is so valuable as a teaching tool. Because strength alone is not enough, you have to time the movement properly. Anyone who masters butterfly has learned to work from the torso instead of the arms — and that transfer is the real gain for every other stroke. In our triathlon training guide, butterfly therefore appears as a technique block, never as distance work.

The body wave: the engine, not the arms

The one decisive image in butterfly is the wave. The body does not travel flat through the water; it oscillates like a dolphin. The chest dips slightly, the hips rise, then the chest presses back up and the hips follow down. That oscillation comes from the torso — abs, back and glutes — not from the arms and not from the knees.

In practice that means: the head follows the wave, it does not lead it. Lift the head to breathe and the wave breaks while the hips sag. Raise it only enough for the mouth to clear the surface and the line holds. The coaching rule: the back of the head stays close to the surface when breathing, the gaze goes slightly forward and down — never straight ahead.

A useful test at home: lie flat on your stomach, hands in front, and try to create an oscillation with the torso alone in which chest and thighs alternately touch the floor. If you can do that without bending the knees, you have understood the movement.

The two-beat dolphin kick: small on entry, big on the push

One full arm cycle contains two dolphin kicks — not one, not three. That pairing is the heart of the rhythm and the most common reason the stroke dies on recreational swimmers after 25 metres.

• Small kick: It happens exactly as the hands enter the water in front and the chest dips slightly. Short, tight, and its job is to keep the hips up.
• Big kick: It comes at the end of the push, as the hands leave the water at the hips and the arms swing forward. Now the legs whip down hard, the hips lift, and the body can re-enter flat at the front.

Both kicks are a whip from the hip: the impulse starts in the glutes, travels through the thighs and ends in the instep. Bend the knees and start "riding a bicycle" and you create drag instead of propulsion. The foot stays pointed, the ankle loose — ankle flexibility is a genuine performance factor here and can be built with foot mobility work.

The arm stroke: catch position and the underwater-freestyle mistake

The arm stroke in butterfly resembles freestyle but is symmetrical, with one crucial difference: both arms catch at the same time far in front, elbows stay high during the pull, palms face backwards. The pull travels in a shallow half-circle under the body to the hips. What matters is the entry width: hands enter about shoulder-width apart — not across the centreline, not wider than the shoulders, or the body rolls sideways.

The classic beginner error is a pull that goes too far back. Pushing the hands behind the hips pulls you out of your line, the hips sag, and the next cycle starts from a bad position. Better: end the pull when the hands reach hip level and swing forward immediately. Propulsion comes from the middle of the pull, not the last centimetre.

The recovery over water is why most swimmers quit after 25 metres. They carry the arms forward with straight, stiff elbows, which brakes like a sail. Correct is: elbows slightly bent, hands relaxed, arms as close to the surface as possible — the famous "low, flat recovery". It costs far less strength and creates far less air resistance.

The rhythm as a whole: what happens when

The four components only work together when the timing is right. One complete cycle looks like this:

• Entry: hands enter shoulder-width in front, chest dips slightly, small kick.
• Catch and pull: elbows high, hands pull under the body towards the back. The head stays low, the gaze goes down.
• Push and exit: hands leave the water at hip level, simultaneously the big kick fires — this is the head's highest point.
• Breathing: the mouth clears the surface only in this short window. One breath per cycle, never two.
• Recovery: arms swing forward flat, hips stay high, the next entry point is already reached.

Start the breath too early — during the pull — and you lift the head, break the wave and lose the rhythm. Start it too late and there is no window left, so you have to lift the head. The window is narrow: it sits between the end of the push and the start of the recovery, roughly 70 to 80 percent into the cycle. That is why good butterfly looks "slow" — the movement flows rather than thrashes.

The six-week build-up — without frustration

The biggest mistake in learning the stroke is starting with full strokes. A realistic build-up uses partial movements, each isolating one element:

• Weeks 1–2: dolphin kick. 8 x 25 metres on your back, arms at your side, only the wave from the torso. Then face down, arms extended forward. Goal: an even rhythm with no knee bend.
• Week 3: single-arm butterfly. One arm pulls while the other stays extended forward; switch arms every 25 metres. Trains timing and feel for the water without the strength problem of symmetry. Two or three sets of 4 x 25 metres.
• Week 4: freestyle-butterfly mix. Three freestyle strokes, one butterfly stroke, three freestyle strokes. The body learns to switch patterns without losing body position. 6 x 50 metres.
• Week 5: short butterfly repeats. 8 x 15 to 20 metres with full technique, 30 seconds rest between. Short and clean instead of long and sloppy.
• Week 6: integration. 4 x 25 metres of butterfly at the end of a freestyle session, plus one set of kick with a board as a technique finish.

The progression sounds slow but it is the fastest route. Force 50 metres unbroken in week one and you produce exactly the errors — high head, bent knees, stiff arms — that you then have to unwind laboriously later.

Technique drills that actually deliver

• Underwater dolphin: after the push-off, 15 metres of dolphin kick underwater, arms extended forward. Trains the wave and the streamline at once — the single best drill there is.
• Vertical dolphin: in deep water, upright, arms at your side, keep your head above the surface with the wave alone. Immediately shows whether the impulse comes from the torso or the legs.
• Kick with board and breathing window: dolphin kick with a board in front, one breath every four kicks. Forces an even rhythm.
• Single-arm butterfly with fins: fins amplify the wave and make it tangible. 4 x 25 metres per side, then repeat without fins — the difference shows how much you contribute yourself.
• 3-3-3 rhythm: three butterfly strokes, three freestyle strokes, three butterfly strokes. The switch sharpens body awareness more than monotonous butterfly.

How much butterfly belongs in endurance training

For triathletes and endurance athletes there is a clear rule: butterfly is technique and strength work, not volume work. Five to ten percent of weekly swim volume is plenty — at 8 kilometres per week that is 400 to 800 metres, split into short sets. Two or three sessions per week with one short butterfly block each is enough.

The benefit is not butterfly performance itself but the transfer: better torso stability, a more deliberate kick in freestyle, and a finer sense of body position. Swimmers who regularly do dolphin kick usually improve their freestyle technique too, because the kick comes from the hip instead of the knee. And the torso strength the stroke demands is exactly what holds the body line in open water — more on that in core training for endurance athletes.

A word on shoulders: butterfly loads the front of the shoulder more than any other stroke. When you are pre-fatigued from freestyle or strength work, butterfly belongs at the start of the session, not the end. If shoulder pain develops, pause the stroke and continue with single-arm butterfly.

Common butterfly mistakes

• Head too high. The most common and most expensive error: it breaks the wave, the hips sink, drag rises. Fix: gaze down, lift the head only enough for the mouth to clear the surface.
• Kick from the knee. "Bicycle riding" creates braking drag. The impulse must come from the glutes, knees stay almost straight during the big kick.
• Too few or too many kicks. Two per cycle is the norm. One makes the stroke flat, three make it hectic.
• Arms too far back. The pull ends at hip level, not behind the body. Otherwise you tear yourself out of your line.
• Recovery with straight arms. A flat, relaxed recovery with slightly bent elbows saves strength and air resistance.
• Too much distance too early. 15 to 25 clean metres are worth more than 50 metres in fight mode.

How Peakora builds swim technique into your plan

In the Peakora engine, technique blocks are a fixed part of swim sessions — they appear as their own block before the main set, with clear instructions on distance, repetitions and rest. For butterfly that means short sets at the start of a session while the shoulders are fresh, and in weeks with a high overall load the plan automatically reduces the technique share so the shoulders do not accumulate fatigue. How sessions are structured is covered in swim training sets explained.

Frequently asked questions about butterfly

Is butterfly suitable for beginners?

Yes, in reduced form. Dolphin kick on your back, single-arm butterfly and short repeats of 10 to 15 metres build the movement. If you can swim 200 metres of freestyle with confidence, you can start — a clean body wave matters far more than strength.

How many dolphin kicks belong to one arm stroke?

Two. The small kick happens as the hands enter the water, the big powerful kick at the end of the push. Both originate in the torso, not the knees.

Why does butterfly tire me out so quickly?

Because butterfly costs roughly 20 to 30 percent more energy than freestyle at the same speed. The arms recover over water against gravity and there is no alternating phase to relax in. Short repeats with clean technique help more than long sets with a dying stroke.

How much butterfly should a triathlete swim?

Five to ten percent of total swim volume is enough. Two or three short sets per week — for example 8 x 25 metres — improve torso stability and feel for the water without overloading the shoulders.