Butterfly Wave Rhythm: Force Distribution Between the Two Kicks

Butterfly is known as “the most beautiful stroke,” but it is also the most energy-demanding. Its signature movement is two dolphin kicks per stroke cycle—the “entry kick” and the “exit kick.” These two kicks are not applied with equal force; each has its own specific role.

1. The Roles of the Two Kicks

Kick	Timing	Function	Force Share
First (entry kick)	When hands enter the water	Propulsion, balance	Approximately 40%
Second (exit kick)	At the end of the pull, when hands exit the water	Primary propulsion	Approximately 60%

2. Four Key Points of the Wave Rhythm

Point 1: Hand Entry + First Kick

• Hands extend forward into the water, shoulders pressing forward
• Simultaneously, legs kick downward while the hips rise
• The body is at the lowest point of the “wave” shape

Point 2: Catch + Hip Rise

• Hands begin the catch (similar to freestyle EVF)
• Hips reach the highest point at the water surface
• This is the crest of the “wave”

Point 3: Pull + Second Kick Preparation

• Hands push through to the thighs
• Legs recover in preparation for the second kick
• Body prepares to breathe

Point 4: Exit and Breathe + Second Kick

• Hands exit the water and recover forward
• Simultaneously, legs kick forcefully downward
• Head lifts to breathe (breathe every 1 or 2 strokes)

3. Hip-Driven Principle

Butterfly kick is not “the legs kicking”—it is “the hips driving the legs”:

1. The hips undulate up and down, like the root of a whip
2. The motion transfers to the knees (middle of the whip)
3. Finally reaching the feet (tip of the whip) to generate propulsion

Test: During kickboard butterfly kick, if the knees bend significantly while the hips stay still, that is an incorrect “leg kick” rather than a “hip kick.”

4. Breathing Rhythm Options

Rhythm	Breathing Frequency	Suitable Distance
1:1	Breathe every stroke	200m butterfly
2:1	Breathe every 2 strokes	50–100m butterfly
Mixed	No breathing during sprint segment	Final 15m of 50m

5. Elite Swimmer Data

Using elite men’s 100m butterfly (51 seconds) as an example:

• Stroke count: approximately 14–16 per 50m
• Breath count: approximately 7–8 per 50m
• Second kick amplitude: hips undulate approximately 30 cm
• First kick amplitude: approximately 20 cm

6. Common Mistakes

Mistake 1: Equal Force on Both Kicks

Causes rhythm disruption and wasted energy.

Correction: Deliberately kick lightly on the first kick and heavily on the second; practice with counting drills.

Mistake 2: Hips Not Moving

Kicking only with the knees creates excessive splash and insufficient propulsion.

Correction: Underwater kickboard butterfly kick—hold the kickboard against the water surface with both hands to force hip-driven movement.

Mistake 3: Breathing Too High

Lifting the head too high causes the lower body to sink, making the next stroke entry difficult.

Correction: Keep the chin close to the water surface; look forward rather than upward.

Mistake 4: Insufficient Arm Strength

Trying to muscle through the pull only leads to increasing fatigue.

Correction: Strengthen the latissimus dorsi and core; add pull-ups and lat pulldowns to strength training.

7. Progressive Training Plan

Phase	Focus	Training Volume
1	Kickboard butterfly kick, find hip drive	200m butterfly kick per session
2	Single-arm butterfly (one arm at side, one arm doing butterfly)	4×50m
3	3-stroke full stroke + 2-kick drill	8×25m
4	Integration training	50–100m repeats

8. SWOLF Goals

25m butterfly SWOLF:

• Elite men: 30–35
• Elite women: 33–38
• Advanced enthusiasts: 40–50

Conclusion

Butterfly may appear to be dominated by strength, but it is entirely a display of rhythm and technique. A slender swimmer with precise rhythm can swim far faster than a strong swimmer with disordered timing. Refining the wave rhythm is the essential path to advancing in butterfly.

Related Reading

• Butterfly Dolphin Kick and Body Wave Coordination Training
• Butterfly Wave Movement: Chest and Hip Rise-and-Fall Coordination Training
• Butterfly Entry and Exit Rhythm: Balancing Streamlining and Propulsion
• Butterfly No Longer a Nightmare: A Scientific Breakdown of Dolphin Wave, Double Kick, and Energy-Saving Rhythm