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Butterfly Stroke Analysis

The butterfly is one of the most difficult strokes to swim because it needs a significant amount of power, strength, and technique.

In this article, we will try to break down this stroke into many components so the Coach, strength trainer or even the Athlete can understand it and swim it better.

1- The Muscles used in Butterfly:

The Butterfly stroke relies a lot on the upper body but relies more on the lower part of the Body.

The Dolphin kick when performed correctly and strongly will increase the speed and reduce the drag.

The major muscles used in this stroke are:

A- Upper Body Muscles:

The Fly (as called by many swimmers) relies heavily on the arms, shoulders and core muscles to propel the body forward in the water.

The primary movers of the butterfly stroke are the pectoralis major in your chest and the latissimus dorsi in your back, which power upper arm adduction

The deltoid muscle which is on the front and back of the shoulders.

The trapezius muscle which is situated beside the shoulders on either side of and behind the neck.

The biceps and triceps muscles play a smaller role.

The abdominal muscles provide also the strength to lift out of the water and then curve in to return.

The Para-spinal muscles along the spine are one of the major muscles responsible of the undulation movement during butterfly stroke.

B- Lower Body Muscles:

The legs offer a great deal of propulsion when swimming the butterfly and gives good forward propulsion when there is little or no propulsion from the arms. As well as propulsion the legs offer balance as the arms recover so the timing of the kick is vital to the butterfly swimmer.

And the primary lower body muscles are :

The gluteal muscle group which drives the recovery phase of the kick and the hamstring muscles which keep the body in a balanced position and aid in the propulsion.

2- Dolphin kick

According to Gary Hall Sr. there are 4 phases of 2 dolphin kicks in every cycle:

Up Kick -Down Kick-Up Kick and Down Kick.

The 2 dolphin kicks are equal in power and size.

And as the Butterfly stroke relies much on the lower body the Upper kick is considered an important part of the dolphin kick as much as the down kick.

Gary Hall Sr. also added that behind every swimmer moving forward is a vortex of water (wake) created by the separation of the water moving along the body (as the body moves forward). This vortex creates a stream of water that follows the swimmer. The bigger and the faster the swimmer, the bigger the vortex and the faster the stream is moving. Since the propulsion from the feet is occurring, for the most part, within this stream, the stream affects the dynamics of the kicking motion.

The feet can create propulsion on both the down and the up kicks. The reason is that the feet need to be moving backward relative to the water only, and since the water is moving forward, propulsion can occur when the feet are moving upward or downward, in addition to backward.

3- Body Position & breathing:

When swimming the butterfly, the body position is very important to minimize the frontal drag, especially during the breathing phase.

The body must be as horizontal as possible to reduce the frontal drag and maintain the speed.

The head position is very important to preserve the best horizontal position. If we raise the head too high when breathing or putting it too low when in the water, we will increase the coefficient of resistance in both cases.

That’s why, it is important to learn how to breathe, so the shoulders stay down and the body position is horizontal.

First advice is to breathe with the neck muscles instead of the shoulders: When raising the head, try to straighten your neck muscles to the front as far as possible and use your head weight to keep the body on the same position and move it forward.

When putting the head down, try to snap it quickly and let the chin touch your chest to transfer that kinetic energy to the front, especially with the arm recovery phase.

Breathing can be either on the side or on the front. Every swimmer can adapt the best type for himself according to his comfort in the water.

Breathing to the front gives the swimmer a clear vision of the wall and a good amount of air but requires focusing more on the shoulders and chin height on the surface of the water.

Side breathing allows the swimmer to keep the shoulders down and increase the number of strokes but will not get a clear vision or big amount of air when breathing.

4- Underwater Pull & Recovery:

There are no pauses or glide when swimming butterfly. It is a circle stroke and not a square one so when the hands enter the water, the swimmer must initiate the pull and focus on the high elbow position to maintain the strongest force.

Fingers position towards the bottom of the pool and the hands accelerate when passing the hips during the push phase.

The swimmers must always keep his arms close to the body and not in a wide position with a focus on a high elbow position.

During the Recovery phase, the arms must be very relaxed and extend backward as far as possible.

5- Butterfly Keys:

The key to master butterfly is Undulation, Breathing, and Tempo.

We know that the center of gravity of a body which is floating in a prone position is the lumbosacral region (Lower Back)

So the secret to a good undulation is to always keep the hips high and the chest down pressed to the surface of the water.

The legs will move as a consequence of the undulation phase and not the opposite.

A good undulation will lead to an increase of speed, reduction of resistance, easy movement of the arms and to a good breathing pattern.

Breathing as explained in the previous sections: The chin must stay low to the water when breathing to eliminate wasted time and unnecessary progression.

The swimmers must swim to the end of the pool and not up in the air.

The butterfly needs a significant amount of strength and power, that’s why tempo is very important to prevent slow swimming and avoid dropping the hips and consequently raise the head and shoulders when breathing, which results to a very big frontal drag and decrease on the swimming speed.

Counting the cycles give the swimmer some rhythm when swimming butterfly.

It will help him determine his efficiency in the water and give him a good landmark of his progression and even speed through the water.


- Gary Hall Sr. Articles ((10-time World Record Holder, 3-time Olympian).

- Kiefer swim Tips.

- Phlex Swim Stroke Clinic

- Pubmed – Scientific Articles.


Sport Tips & Analysis

by Zied Abbes

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