A Witi on the Splendiferous Butterfly
An Exposition on How the Butterfly is Swum

The butterfly swimming stroke was born in the 1930’s while its namesake, the butterfly insect, has been around for possibly 100 million years. Each is the most beautiful of its kind to watch. To achieve its goal, the insect develops in rudimentary stages and must go through metamorphosis to advance from its lowly caterpillar phase into a magnificent butterfly. To become a butterfly swimmer, the most difficult stroke to master, one must be willing to go through being atrocious and making solid progress in order to become … lousy, long before becoming splendidly elegant. For most, the metamorphosis is not automatic. Either good coaching or diligent study matched with hard work is needed to meet the challenge. It’s about properly making into habit all of the many aspects of the stroke. Making and refining these habits takes a great deal of time and a lot of re-going-over one’s form.
One may be lucky just to have a swimming pool available, or, be blessed to have their underwater swimming form video-recorded for review with an expert coach as they progress. One’s goals and means determine the choices for the preparation and learning method. The student may do targeted drills and exercises, the most effective way to learn, or just dive in. Regardless of the approach, studying underwater video of a variety of accomplished swimmers is a valuable aid. There’s a surprising lot to think about which keeps it fun. Swimming butterfly should lead to being wonderfully fit, although it helps immensely to be physically fit apart from swimming it.
The foundation of the butterfly stroke is a rhythmic undulation of the torso and legs. From head to toe, the body snakes a sleek splendent path assisted by driving arms that circle in parallel and swing through the air with grace. Fly is its perfect nickname.
Full body undulation involves forward and downward motion starting with the head, shoulders, and chest, followed in sequence by downward pressure with the stomach, thighs, lower legs, and feet. Conversely, undulation is the homologous raising of the head, chest, stomach, thighs, lower legs, then feet. The objective of all motion is to drive the body forward. To maximize the objective, energy is evenly distributed. Undulation is not exaggerated; its motion is smooth and fluid, minimizing unneeded drag, the complementary essential goal. As with breaststroke, a central pivot for undulation (often referred to as an “axis”) is at the hip joints. Butterfly isn't sharply divided like breaststroke so its midbody axis is less pronounced. What’s important is that all parts of the body work together, in sync, and no aspect of the stroke is dominant over another.
The leg motion of the butterfly stroke is the aptly-named dolphin kick. The dolphin kick was also developed in the 1930’s and quickly merged with the nascent butterfly stroke. The butterfly had been developed from the breaststroke.
A strong midsection and substantial upper-body strength, but not necessarily muscle mass, are important for swimming the fly. Shoulder, back, knee, and weight problems are obvious examples of obstacles. Superior flexibility is a major asset (including good thoracic spine extension), but, for the most part, it is not an absolute necessity. The feet and ankles must flex considerably to perform the dolphin kick well, even so, that’s predominantly true for all the swimming kicks. If desired, ankle flexibility can be improved by training with fins. Fitness conditioning for the legs and feet helps to eliminate cramping, and stretching is helpful for plantar flexing the feet (pointing downward).
The dolphin kick is an underwater kick which is done with the legs close to each other, the feet angled inwards and back (plantar-flexed), and the toes bent slightly to correspond to the movement of the feet. The big toes are kept close to each other but do not touch. As the legs move up and down in parallel, flexing of the ankles and feet sweeps water, producing considerable force.
The dolphin kick is used at some point in all of the four competitive strokes. For the breaststroke, only one dolphin kick is allowed at each turn. The other racing strokes use the dolphin kick freely when coming off the walls and butterfly and freestyle also use the dolphin kick for propulsion when coming off the blocks until the surface stroke begins. Ostensibly, the underwater dolphin kicking is the fastest part of the race—it can be faster than surface strokes because there’s more resistance at the surface. The legs and feet whip or snap with the lower body completely dominating propulsion—yet the underwater dolphin can only maintain initial speed (from the dive or the push off the wall), never adding to it. The dolphin in butterfly is different because the undulating torso is at the surface and kicking is an extension of the rest of the stroke, matching its rhythm. Its role in propulsion becomes supportive.
Most discussions on swimming technique, whether directed at recreation or competition, look to what maximizes efficiency and performance, and that’s true here. Bodies are unique and often there are more than subtle differences in form not necessarily related to whether one is cruising or racing. Basic technique allows for individual variations. Non-competitive swimmers frequently model the styles of competitive swimmers even if paying less attention to starts and turns. Butterfly stroke synchronization or timing tends to improve at faster speeds, and when training for competition, it's necessary to routinely swim fast, even more so than for the other strokes. Nevertheless, slower swimming may mean more swimming and more thorough development for many aspects of the stroke.
To casually begin swimming the butterfly (and to ease into exposing the details of the stroke), one positions the body at the surface in the streamline position with forward momentum—body straight, face down, arms forward with one hand on top of the other—and the full stroke is begun by bringing the arms down simultaneously with the legs. For each revolution of the arms there is one full undulation yet two kicks (an additional kick, #1, is inserted to support descent at the end of the recovery phase). The two down-kicks must occur (1) when the arms are at full forward extension (hands entering the water) and (2) when the arms are back and the hands are about to leave the water. The down-kicks are of similar intensity.
A common disabling error for beginners is the premature execution of down-kick 2. (Some succeed with a faint or no second kick, especially kids whose legs are weaker.) Down-kick 2 can be thought of as a direct result of full body undulation and it initiates arm recovery, whereas down-kick 1 occurs to assist and balance the downward motion of the upper body and arms after recovery. There is more time between the start of kick 1 and the start of kick 2 than between the starts of kick 2 and kick 1; simply put, kick 1 is the longer kick. Both down-kicks finish with the legs straight at the knees and the lower legs immediately return upwards. The lower legs rise during the arm pull, and after down-kick 2, the lower legs are in up motion for most of the recovery. Up and down lower-leg motion never stops. Ordinarily, and because of human anatomy, more force is applied on the down motion. The kick improves when force becomes more symmetrical through training. The legs stay loose at the knees. The end of a down-kick is the start of an up-kick and the end of an up-kick is the start of a down-kick. Correctly done, the hips automatically retain proper height. The primary role of the kick in butterfly is to act as a counterbalancing force in undulation and for arm motion. The large majority of the kick's thrust comes from the ankles and feet.
The lower legs do not thump the water which creates drag. To some degree, the chest passes through the same water and space the head, then shoulders, first went through, followed in turn by the rest of the body. Ideally, the feet do not break the surface but come right up to it, although it's ok should the heels surface.
It can be valuable to describe any part of the butterfly stroke with respect to any other part, especially those that are happening simultaneously, or, in succession. Just the same, it’s helpful to isolate parts of the stroke.
With the trunk extended for arm recovery, the arms enter the water relaxed, straight in front, typically shoulder-width (or more) apart. The catch is slow starting because the head and shoulders must go underwater before the hands. The hands enter the water slightly angled, thumbs and forefingers first. Forward momentum and force from the kick push the hands downward. Fingers are initially curved or slanted to abet downward motion; the outward and downward angle of the hands on entry varies with the swimmer; hands proceed through a seamless short-out-and-down-sweep-in motion; fingers quickly flatten with the palms. Depending on the swimmer, fingers may be either slightly separated or close, but not pressed together; the thumb may be partially brought in too. The pull begins when the hands rotate to palms facing back (or back of hands facing forward). Even though the arms are moving slowest when extended forward, there is no pause in motion (barring distance swimming or otherwise using a gliding technique which disrupts normal undulation).
The majority of the stroke's propulsion comes from the hands and arms. Hand pressure is predominant, but propulsion generated from wrist and forearm pressure is important as it enhances and combines with hand pressure. As the arm pull begins, the elbows are pulled outwards. Immediate pressure is put on the forearms to swing below the elbows rather than move equally with them—elbows remain high. As the forearms approach the downward vertical position, upper arm force also becomes directly propulsive. The entire arms and the shoulders are used to generate power; full and increasing force is sustained into the push, with the palms noticeably dominant. The shoulders and elbows are prepared and positioned for the exit part of the recovery. At exit, the arms must erupt in an outward motion as the shoulders reach peak height.
As the forearms and hands begin the pull, each arm arcs as the hands sweep towards each other below the neck or chest, with the hands subtly pushing downwards to create lift. Then the press is straight back. The hands retain their general direction—palms facing back of pool, fingers pointing to the bottom—as they push under the body and towards the waist. There is natural variation even among top swimmers on how close the hands come to each other and at what point they’re closest when underneath the body. The push can be thought of as driving the head up and forward; breathing would begin just before the hands leave the water. When the hands are at their lowest point, the shoulders are out of the water and a down-kick begins. The hands and arms make an outward and upward push around the hips closely before they release the water. Led by outward sliding arms, still bent at the elbows, the palms face back and up while sliding outwards at exit. The arms are thrust into exit-recovery without effectuating drag. Undulation sustains momentum. The arms extend wide and roll during recovery, and remain straight through reentry. Arms and hands land softly and gracefully as the head and shoulders go down and forward; the hips go up with the down-kick.
The breathing stroke is largely the same as the non-breathing stroke: head and shoulders rise early in the pull; when not breathing, the shoulders reach near the same height out of the water as they do for breathing. For breathing, both the head and shoulders are lifted no more than necessary and then quickly drop forward into the water. The face points down and ahead when taking a breath, then retreats with the shoulders but may retain a good portion of its breathing-in angle when underwater. The head goes to the same depth as the shoulders, not more; optimal depth varies with the swimmer. Upward undulation provides lift for breathing and the lower body going down makes it easier to lift the arms.
Breathing is relaxed. The swimmer breathes out continuously while underwater and blows out with the mouth open before surfacing for the breath. Exhalation begins when the head enters the water. Breathing every other stroke, and breathing every stroke, are both common breathing methods.
The goal is to attain an automatic, consistent form; but not so automatic that improvement must cease or form regress. Achieving consistency is made difficult by the physical demands of the stroke. It's likely that the flyer will be swimming at distinct levels of energy and fitness. Technique cannot be learned when one is very tired although swimming when tired is necessary to achieve and maintain the wanted degree of fitness. One must be mindful and always train within their limitations. Learning can be a battle because it’s only possible to concentrate on one or two aspects of the stroke at a time while trying not to let bad habits creep back in, which, of course, is a reason why there are drills for many elements of fly.
A common problem is trying to get too much out of the kick. A contrasting problem, in part, is trying to power the stroke with the arms and having a soft to non-existent kick. And those problems can be paired with either the problem of weak core undulation, or, its relative opposite, not undulating in a slender profile. Obvious areas of concern are the shoulders being elevated too high, and taking too long to breathe. However, there are swimmers who find it more efficient to lift the head comparatively high for breathing, and a last second, sharp drop of the head back into the water boosts forward motion after recovery.
The dominant impetus of undulation is a repeating up-and-forward thrust rather than an up-and-down cycle. The midsection, or core (abdominal, back, and hip muscles), is the heart and strength of undulation. Excessive hip movement implies wasted energy and lessens the amount of streamline that can be attained. With balance in undulation comes smoothness, and the hips are automatically kept properly elevated. The hips are naturally a few inches higher after down-kick 1 than after down-kick 2, and the lower hip position for down-kick 2 makes it easier to raise the arms.
Hard things to learn can be executing the second kick at the right time and not over-kicking. Fortunately, once one finds the correct timing of the kicks and undulation, it should lock in never to be the same problem again. Nevertheless, a small correction in timing can be made if necessary to align undulation and improve propulsion going into recovery, the slower and least propulsive part of the stroke. The correction could be slowing the undulation to allow the arms to catch up, although in most cases what's needed is to move the arms faster through the pull. (The “hand as an anchor” tenet and metaphor notwithstanding.)
The over-kicking problem may not be dispensed with so abruptly, yet it also reveals a deficiency with undulation and it is manifested in the problem of down-kicking too hard from the knees, or kicking too far. It's easy to overdo the dolphin kick in butterfly because (unlike the flutter kick in front crawl and backstroke) the knees are loose and bend considerably and there is instant gratification from kicking hard. Kicks originate from the upper legs (and hips) which are slower moving than the lower legs. The upper legs provide resistance for the lower legs at the finishes of both the up and the down kicks. The lower legs sweep up and down with amplitude not being too much, or too little. Often, a predictable way to improve is by developing a faster and shallower kick to lessen drag. This may be accompanied by a faster arm pull. It may be helpful to think of getting the most push out of the kick rather than the most power.
The swimmer's body creates a vortex of forward moving water in which the feet kick, meaning the kick inherits the benefit of a supportive stream. This, and the elongation and motion of the feet combine to achieve pushing. Kicking needs to stay below the surface and within the beneficial amplitude. Turbulence from excessive kicking can disrupt laminar flow and result in markedly increased resistance. Prominent turbulence on the surface is a sign the kick is doing more harm than good.
Flyers need to be aware of the depth reached by their head and shoulders, the downward slope , and determine the most comfortable and effective depth for their swimming style. Novice flyers are often advised to pay attention to the height of their rump (“keep your hips up”) which is hard to know precisely even if it is an indication of whether or not one's stroke has fallen apart. Moreover, the up and down movement of the hips (and the central pivot) is a product of overall undulation and thus completely dependent on it. It's more useful to pay attention to the height and the depth reached by the shoulders.
Breathing can be made harder by allowing one's head to drop too far and by looking down and back. The head and shoulders should descend to several inches below the surface but positioning the head to face down and ahead when underwater can make lifting for breathing noticeably easier and therefore improve efficiency. To learn to control the head angle, one should be conscious at all points of where they are looking.
Whether to breathe every stroke, or, every other stroke, is an individual choice. Most flyers breathe every other stroke (less often is an option too), although to cover long enough distances, all would be breathing every stroke. The tradeoff is whether the extra breath of air pays for the extra effort of raising the head. The affect on undulation should be not be great but factors into the equation. For those who do not principally breathe every stroke, doing so for full laps is a good way to work on breathing technique including undulation where it will serve to expose any problems. Flyers need to be able to smoothly switch to breathing every stroke. Breathing to the side is an option that works well for a small percentage of flyers—those who benefit by sacrificing some of the stroke's elegant symmetry.
The keys to breathing are relaxed breathing and breathing out when the head drops back into the water. Inhalation is a normal breath but exhalation is far longer. Swimmers who can learn to comfortably exhale predominantly through the nose may have an advantage. Exhalation is more or less continuous and natural as one can make it, until the next breath. The rhythm of breathing and exhalation changes when the time taken between breaths changes.
The stroke becomes easier as more of its elements are performed consistently and correctly, with stable and level, forward-balanced undulation being particularly important. Most of the driving force is produced by maintaining an effective grab (hold) on the water while quickly pulling the hands inwards towards (a plane below) the base of the neck, succeeding into an accelerating push to the hips, culminated with a clean arm exit—arms whip outwards at elbows as shoulders reach their peak height.
If judging from the observed number of laps swum at the pool, butterfly is the most demanding stroke by far. It’s unforgiving if one thing is off—arms are dead, undulation is flagging, the water is choppy and cold. The consequence of falling out of form is lethal: insufficient or late lift for breathing. Most disruptions are impossible to recover from. There’s no faking in fly.
The downright laborious effort required of a developing flyer to reach a new level of competence and modest gleam of beauty is, nonetheless, all but guaranteed to invigorate.
This exposition is now complete. Sustentative silk has been sewn for a flyer, in due time, to leave the pupa behind. Silk releases enduring and ravishing quality yet genetics fashion the nature of the rapture. Be it the iridescent Blue Morpho, the Monarch, Swallowtail, Queen, Viceroy, Knight, Painted Lady, Sylphina Angel, Red Admiral, Ulysses, King Copper, Tawny Coster, Velvet Flat, Crimson Patch, Mourning Cloak, Sordid Emperor, Gaudy Baron, Grand Duke, Dogface, Tree Nymph, Mamba Swordtail, Lesser Zebra, Jungle Glory, Giant Glasswing, Grey Albatross, Golden Glider, Dingy Skipper, Common Lime, Question Mark, Small Greasy, Narcissus Jewel, Cracker, Great Spangled Fritillary, or, be it (and now can be known as) the Splendiferous butterfly swimmer!     butterfly insect
This short but exquisite video from Michael Phelps is among the best for illustrating good butterfly technique. It includes slow motion and desired frames can be viewed by pausing or scrolling, starting from within the first second. Phelps, the most accomplished swimmer and butterflyer, illustrates perfect form despite that some of it is not the ideal for most swimmers or bodies. Michael has a proportionally-large upper body, and he descends deeper than most; his arm entry is wider than most, and always breathing on every stroke (its increase in popularity notwithstanding) is not optimal for most swimmers. Nevertheless, his talent, the ease at which he swims (with no wasted motion), and his superior flexibility in the shoulders, elbows, knees, ankles, and feet, only help to exemplify proper technique.
Tyler Clary is an immensely skilled swimmer and also a decorated Olympian. Tyler is the star for a two-minute, instructional video produced by swimming gear company Speedo. This video has multiple narrations and the version referenced here emphasizes a high elbow position during the pull. Tyler is stated to have “great mobility” in his shoulders. A high elbow position is associated with the “early vertical forearm” technique that is shared with freestyle. All of the four main strokes make strategic use of bent elbows, largely to position the hands as early as possible in the optimal angle of force in relation to the direction of the body, along with the benefit of getting the most supplemental force from the forearms and wrists. In butterfly, the early movement of the elbows is a consequence of swinging the forearms and hands below the elbows (a carefully learned technique) as they're swept inwards and towards each other. The swimmer can focus on the movement and position of the forearms and hands while keeping the elbows high. This is sometimes likened to “reaching over a barrel.” Here is the Clary video – it will open in a separate window. Tyler brings his hands close together as do many flyers.
Australian Stephanie Rice is another champion swimmer and decorated Olympian. She has provided thirteen minutes of superior swimming in slow motion video. All four strokes are exhibited; the first four minutes are of butterfly. Here is the Rice video – it will open in a separate window.
Now we switch to full-speed clips of butterfly racing. It's worthy of note that many top flyers are also among the best at the individual medley. The first clip is the 2014 Pan Pacific 200 meter final with Japan's versatile and talented Daiya Seto as the main star (2:29). Next is a short segment of Phelps swimming 200 meter fly at the 2003 Barcelona Worlds (0:53). Here is the complete underwater view of Milorad Cavic and Phelps racing for 100 meter gold at the 2008 Beijing Olympics (1:16).
Here are two more instructional videos. The first features all-time great Ryan Lochte demonstrating how to turn in fly (2:17). Next is coach Bob Bowman narrating Swim Fast Butterfly with Michael Phelps in a six-minute segment focusing on butterfly training taken from a 42 minute video produced after the 2000 Sydney Olympics.
An oft-mentioned butterfly training drill is the “one-arm fly drill” (single-arm drills are also used for front crawl and backstroke). Prerequisites before attempting full-stroke fly should be having practiced undulation (including “body dolphin”) without any arm stroke, and having practiced butterfly arm stroke without any kicking. Olympic gold medalist and now coach, Josh Davis, in a promotional video, presents a drill he calls “Angels in the Water” which is for practicing only the butterfly arm stroke (3:07). More so than for the other strokes, it's hard to get rid of bad habits in fly; so a goal should be to (do one's best to) avoid making them.
WIRED magazine published this video of swimming insights (2:42) from American gold medalists Clary, Lochte, Elizabeth Biesel, Matt Grevers, Nathan Adrian, and Conor Dwyer. A lot of it is directly related to butterfly, and much on the mechanics of swimming is common among strokes.