Swimming

Butterfly

A simultaneous, powerful two-arm pull with an undulating dolphin kick. It is the most demanding stroke on the lats, shoulders and the whole front/back chain of the trunk.

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Swimmer mid butterfly stroke, both arms sweeping forward over the water

Muscles worked

Neck (Front)Upper traps — 30% importance (Front)Front delts — 55% importance (Front)Side delts — 50% importance (Front)Chest — 70% importance (Front)Serratus anterior — 60% importance (Front)Biceps (Front)Forearms & grip — 40% importance (Front)Abs — 85% importance (Front)Obliques — 30% importance (Front)Hip flexors — 65% importance (Front)Quads — 35% importance (Front)Adductors (Front)Shins (tibialis) (Front)Calves (Front)Outer shins (peroneals) (Front)Feet (arch & toes) (Front)Neck (Back)Upper traps — 30% importance (Back)Upper back (rhomboids, mid/lower traps) — 55% importance (Back)Rear delts — 55% importance (Back)Side delts — 50% importance (Back)Rotator cuff — 75% importance (Back)Lats — 100% importance (Back)Lower back (erectors) — 65% importance (Back)Triceps — 80% importance (Back)Forearms & grip — 40% importance (Back)Hip abductors (glute med) (Back)Glutes — 60% importance (Back)Hamstrings — 30% importance (Back)Adductors (Back)Calves (Back)
FrontBack
  • Lats
  • Abs
  • Triceps
  • Rotator cuff
  • Chest
  • Hip flexors
  • Lower back
  • Serratus

The movement, phase by phase

  1. Entry & catch

    Hands enter shoulder-width, arms rotate internally and set a high elbow to "grab" the water.

    • Shoulder rotation
    • Front raise (shoulder flexion)
    Neck (Front)Upper traps (Front)Front delts — primary (Front)Side delts (Front)Chest — primary (Front)Serratus anterior — primary (Front)Biceps (Front)Forearms & grip (Front)Abs (Front)Obliques (Front)Hip flexors (Front)Quads (Front)Adductors (Front)Shins (tibialis) (Front)Calves (Front)Outer shins (peroneals) (Front)Feet (arch & toes) (Front)Neck (Back)Upper traps (Back)Upper back (rhomboids, mid/lower traps) (Back)Rear delts (Back)Side delts (Back)Rotator cuff — primary (Back)Lats (Back)Lower back (erectors) (Back)Triceps (Back)Forearms & grip (Back)Hip abductors (glute med) (Back)Glutes (Back)Hamstrings (Back)Adductors (Back)Calves (Back)

    Best exercises for this phase:

  2. Pull (in-sweep)

    Arms sweep down and in under the body — the main propulsive phase driven by the lats and chest.

    • Straight-arm pull (shoulder extension)
    • Vertical pull
    • Fly / hug
    Neck (Front)Upper traps (Front)Front delts (Front)Side delts (Front)Chest — primary (Front)Serratus anterior (Front)Biceps (Front)Forearms & grip — primary (Front)Abs (Front)Obliques (Front)Hip flexors (Front)Quads (Front)Adductors (Front)Shins (tibialis) (Front)Calves (Front)Outer shins (peroneals) (Front)Feet (arch & toes) (Front)Neck (Back)Upper traps (Back)Upper back (rhomboids, mid/lower traps) (Back)Rear delts (Back)Side delts (Back)Rotator cuff (Back)Lats — primary (Back)Lower back (erectors) (Back)Triceps — primary (Back)Forearms & grip — primary (Back)Hip abductors (glute med) (Back)Glutes (Back)Hamstrings (Back)Adductors (Back)Calves (Back)

    Best exercises for this phase:

  3. Push (finish)

    Hands accelerate back past the hips; triceps extend the elbow while lats finish shoulder extension.

    • Elbow extension
    • Straight-arm pull (shoulder extension)
    Neck (Front)Upper traps (Front)Front delts (Front)Side delts (Front)Chest (Front)Serratus anterior (Front)Biceps (Front)Forearms & grip (Front)Abs (Front)Obliques (Front)Hip flexors (Front)Quads (Front)Adductors (Front)Shins (tibialis) (Front)Calves (Front)Outer shins (peroneals) (Front)Feet (arch & toes) (Front)Neck (Back)Upper traps (Back)Upper back (rhomboids, mid/lower traps) (Back)Rear delts — primary (Back)Side delts (Back)Rotator cuff (Back)Lats — primary (Back)Lower back (erectors) (Back)Triceps — primary (Back)Forearms & grip (Back)Hip abductors (glute med) (Back)Glutes (Back)Hamstrings (Back)Adductors (Back)Calves (Back)

    Best exercises for this phase:

  4. Recovery

    Both arms swing forward over the water — rear and side delts plus upper back lift the arms.

    • Lateral raise (abduction)
    • Reverse fly
    Neck (Front)Upper traps — primary (Front)Front delts (Front)Side delts — primary (Front)Chest (Front)Serratus anterior (Front)Biceps (Front)Forearms & grip (Front)Abs (Front)Obliques (Front)Hip flexors (Front)Quads (Front)Adductors (Front)Shins (tibialis) (Front)Calves (Front)Outer shins (peroneals) (Front)Feet (arch & toes) (Front)Neck (Back)Upper traps — primary (Back)Upper back (rhomboids, mid/lower traps) — primary (Back)Rear delts — primary (Back)Side delts — primary (Back)Rotator cuff (Back)Lats (Back)Lower back (erectors) (Back)Triceps (Back)Forearms & grip (Back)Hip abductors (glute med) (Back)Glutes (Back)Hamstrings (Back)Adductors (Back)Calves (Back)

    Best exercises for this phase:

  5. Dolphin kick & undulation

    The wave starts at the chest and runs through hips to feet: abs and hip flexors drive the down-kick, glutes and lower back the up-kick.

    • Trunk flexion
    • Hip flexion
    • Spinal extension
    • Hip extension
    Neck (Front)Upper traps (Front)Front delts (Front)Side delts (Front)Chest (Front)Serratus anterior (Front)Biceps (Front)Forearms & grip (Front)Abs — primary (Front)Obliques (Front)Hip flexors — primary (Front)Quads — primary (Front)Adductors (Front)Shins (tibialis) (Front)Calves (Front)Outer shins (peroneals) (Front)Feet (arch & toes) (Front)Neck (Back)Upper traps (Back)Upper back (rhomboids, mid/lower traps) (Back)Rear delts (Back)Side delts (Back)Rotator cuff (Back)Lats (Back)Lower back (erectors) — primary (Back)Triceps (Back)Forearms & grip (Back)Hip abductors (glute med) (Back)Glutes — primary (Back)Hamstrings (Back)Adductors (Back)Calves (Back)

    Best exercises for this phase:

Most specific exercises

Drills & sessions in the sport

Work done in the water or on the run itself, next to the strength exercises above.

Common technique mistakes

The technique faults behind most injuries here, and how to fix them.

  • ✗ Undulating from the lower back instead of the chest.

    Why it hurts: Excessive lumbar arching on every stroke causes back pain.

    ✓ Instead: Press the chest down and let the wave travel from chest to hips; the kick keeps it going.

  • ✗ Dragging the arms low through the recovery.

    Why it hurts: The shoulders strain to lift the arms clear, especially when tired.

    ✓ Instead: Swing the arms low and relaxed over the water with the thumbs down, and stop the set when the stroke breaks down.

Training notes

  • Straight-arm pulldowns and pullovers copy the catch-to-pull path better than rows.
  • Train the trunk dynamically (reverse crunches, leg raises, back extensions) — the kick starts at the chest, not the knees.
  • Butterfly overloads the shoulders: always pair pulling with rotator cuff and rear-delt work.

Mobility to pair with it

  • Thoracic extension over a foam roller
  • Lat & overhead shoulder flexion stretch
  • Ankle plantar-flexion (pointing) mobility