Undulation Technique to Improve Your Butterfly Stroke

Undulation Technique to Improve Your Butterfly Stroke

Dr. GJohn Mullen Biomechanics, Blog, Dr. John Mullen, Latest&Greatest, Training 2 Comments

Background On The Butterfly Stroke

If you want to practice the Butterfly stroke on a competitive level, you need to work on the movement which is its basis: the undulation technique. This technique is based on the movement of your body in the water. It requires much higher energy dispersal compared to other techniques.

Let us look more closely at this swimming technique.

Undulation is achieved when the body is in a curved position and the head pushes upwards and downwards so that the entire body moves, producing a wave or ripple as in the butterfly stroke. This allows your body to slide in the water without the need of leg and arm movement. In turn, it allows athletes to save energy and optimize the movement.

The undulation phase includes two important actions that allow the body to move forward near the water surface.

First Phase of Undulation

The first phase starts when the head moves downwards and the chin touches the chest. As the move pushes your shoulders and back downwards, your body gains speed.

Athletes can also be instructed to execute an opposite upward pelvic movement for speed.

Second Phase of Undulation

The second phase starts as soon as you feel your body is moving downwards smoothly and with the required speed. More specifically, the second phase starts when your head quickly moves upwards. Your forehead emerges from the water and you slightly curve your back to use the speed you acquired in the previous phase. You delicately push your pelvis/bottom downwards to intensify the movement, making it smooth and harmonious.

Common Mistake in Learning the Undulation Technique

One of the most common mistakes I have seen my colleagues make is to ask their athletes to use their legs before they have learned the correct undulation technique for the butterfly stroke.

To correctly acquire this technique, leg movements must never be required – legs will move as a result of the undulation. Leg movements must only be required once the athlete could perform the undulation technique impeccably and perfectly over long distances.

Based on my coaching experience, using the legs too soon in this phase will make undulation look contracted and sudden. The center of gravity will have to support an unnatural movement of the back and the trapezius and intervertebral muscles, while you’re performing the undulation technique and the butterfly stroke.

When swimmers strongly push their bodies downwards and upwards in the effort of creating –but failing to achieve –the undulation movement, they put unnecessary stress on their backs.

The complete Dolphin Kick also includes the breathing technique along with undulation. It is possible to breathe at every stroke cycle or every other stroke cycle.

During undulation, air can be taken in front and/or at the sides. Once the stroke cycle starts in the water, the head will go back underwater. The arms will complete their movement in front of the head, slightly above the nape.

Role of Your Arms and Legs in the Undulation Technique

The arms help find an anchorage in the water to stabilize the action, effectively advancing the body. The legs support the undulation created by the head movement. Therefore, if you do not work specifically and in a structured way, you will never obtain a Dolphin Kick with perfect undulation.

Training to Perfect Your Undulation Technique and Improve Your Butterfly Stroke

What suggestions can we give our athletes to help them facilitate and improve their Dolphin kick?

In-water training exercises, such as flip turns, are useful for learning to arch the back. Touching the bottom of the swimming pool helps push the head downwards and make the body follow it.

Athletes could also try out-of-water exercises at the gym to improve this swimming technique. A good example would be exercising with a medicine ball.

You may lie down in a prone or supine position. Following the movement of the ball will let your body adapt to the shape of the ball, simulating the undulation. An alternative is the execution of rolls on a soft mat to focus on the movement of nearing the head to the chest, and so on.

A complete Dolphin Kick requires a perfect undulation technique. The longer the competition, the more swimmers will have to perform these phases seamlessly as they require little energy dispersal but extreme coordination of the HEAD and PELVIS.

Here’s how a methodological sequence from undulation technique to full Dolphin Kick looks like:

  • undulation without arm and leg movements
  • undulation with arms next to the ears
  • undulation with dolphin stroke
  • vertical, supine, and lateral undulation
  • undulation with support, such as flippers, mouthpiece, swimming board

In this point the swimmer increases the speed to support this motion, therefore performing the butterfly stroke better.


  1. http://folk.ntnu.no/oivarn/hercules_ntnu/LWTcourse/lwt_new_2000_Part_A.pdf
  2. http://jeb.biologists.org/content/214/4/561

Written by Livio Cocozza: I have a degree in Sports Science at University of Perugia, Italy. Over the years, I have gained vast experiences in training and coaching swimming and water polo competitions.

Originally Posted June 2017

Comments 2

  1. I agree with the undulation. I am 66 and so many my age cannot do this stroke. I think the confusion is keep the head “neutral”. I like to think it is like a porpoise. They undulate also.

    This a a good article and a good step by step technique of “undulation”

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