Why pulling both arms at once isn't automatically efficient: the keyhole pattern, correct entry width, and the most common power drain.
"My arms get heavier with every stroke, even though I use both at once — isn't that the most efficient way?" The honest answer: simultaneous doesn't automatically mean efficient. Viewed from below, the butterfly arm pull follows a keyhole pattern — the hands enter outside the shoulders, sweep inward, then sweep back outward toward the thighs. That curve, not a straight pull backward, generates most of the propulsion.
The pull breaks down into two propulsive phases. The insweep pulls the hands from outside the shoulders inward, backward and upward to under the chest. The upsweep then carries the hands from under the chest back out toward the thighs. Together, these two phases are why the keyhole shape catches more water than a simple straight pull backward.
But where most pulling power actually leaks away isn't the pull path itself — it's the start: entry width. Hands should enter roughly at shoulder width; the most common mistake among intermediate swimmers is sweeping far too wide on the catch right afterward, sometimes almost a full meter apart. That costs strength without adding propulsion: you're working against yourself instead of with the water.
Let your hands slide into the water right where your shoulders are — not wider. Picture a line directly under your shoulders and aim for it, instead of "somewhere far out front".
Once both hands are in the water, they pull together inward under the body — not diagonally outward. Keep the elbows higher than the hands (high elbow) so you catch water with the whole forearm surface, not just the hand.
After the insweep, the hands reverse direction and sweep back outward, past the belly and hips, ending near the thighs. This second arc delivers the last push before the arms swing back over the water.
After the pull, both arms swing relaxed to the sides over the water surface back to the front — not yanked up tensely. The momentum for this comes from the second kick you learned in the previous guide, not from extra arm strength.
Get filmed from the side or from below. The typical error isn't the basic shape but a too-wide catch right after entry — exactly where many intermediate swimmers unknowingly waste strength.
A high elbow takes load off the shoulder — a dropped, extended elbow forces the shoulder joint into unfavorable internal rotation, which invites irritation over time. If you feel a pulling or stabbing sensation at the front of the shoulder, that's often a sign of exactly this error, not "too little strength" — reduce pace and volume rather than swimming through it.
Practice the keyhole path first on land, standing with a slight forward lean: hands at shoulder width out front, then slowly trace the arc inward and back outward. This trains the movement pattern in your mind without breathlessness or water pressure distracting you — and that mental picture is exactly what's missing for most swimmers who just "pull backward somehow".
A pull shape that looks like a keyhole viewed from below: hands enter at shoulder width, sweep inward (insweep) and then back outward toward the thighs (upsweep). This curve catches more water than a straight pull backward.
Roughly at shoulder width. The most common mistake among intermediate swimmers isn't the entry itself but catching too wide right afterward — sometimes almost a full meter apart, which costs strength without adding propulsion.
A high elbow lets you catch water with the whole forearm surface instead of just the hand — that means more propulsion for the same effort while also taking load off the shoulder joint.
Maybe simpler, but less efficient. Modern elite swimmers do often swim a somewhat straighter pull than was traditional, but the underlying insweep-upsweep motion remains the core of the propulsion.
Breathing in Butterfly: Timing Between Air and Speed