Swimming Butterfly Stroke: How to Fix Sinking Hips and Improve Your Undulation

Why Hips Sink in Butterfly

Butterfly is the most technically demanding swimming stroke, and sinking hips are the most common problem beginners and intermediate swimmers face. When your hips drop, your body creates a steep angle in the water — like a boat bow-up — which dramatically increases drag and forces your arms and legs to work much harder to maintain speed.

The root cause is almost always incorrect body undulation. Butterfly is a wave-like movement that travels from your chest through your hips to your feet. When swimmers try to power through with their arms and ignore the wave, the hips inevitably sink.

The Undulation Principle

Think of butterfly as a dolphin movement, not a power movement. Your chest presses down into the water as your arms enter, which causes your hips to rise. Then as your arms pull through, your chest rises and your hips drive down to initiate the kick. This wave motion is what keeps your hips at the surface.

A common mistake is trying to keep the body flat and horizontal. This actually works against you — butterfly requires deliberate up-and-down movement to generate propulsion efficiently.

The Two-Beat Kick Timing

Butterfly uses a two-beat kick per arm cycle. The first kick happens as your hands enter the water at the front of the stroke — this is the smaller kick that initiates the wave. The second kick happens as your hands pass your hips during the pull phase — this is the power kick that drives you forward and lifts your hips for the recovery.

Most swimmers with sinking hips are either missing the first kick entirely or kicking at the wrong time. The timing must be precise: kick as your hands enter, kick again as your hands exit.

Head Position and Breathing

Your head position has a direct impact on your hip position. If you lift your head too high to breathe, your hips will drop immediately. The correct breathing technique is to lift your chin just clear of the water — not your whole head — and breathe forward, not upward.

Practice breathing every two strokes rather than every stroke. This reduces the frequency of the hip-dropping breathing movement and allows you to maintain better body position for longer.

Drills to Fix Sinking Hips

Single-arm butterfly: Swim butterfly using one arm at a time while the other arm stays extended in front. This forces you to focus on the wave movement and kick timing without the complexity of the full arm stroke.

Dolphin kick on your back: Lie on your back and practice the dolphin kick without any arm movement. This isolates the hip-driven wave motion and helps you feel the correct undulation without the distraction of arm technique.

Chest press drill: Stand in shallow water and practice pressing your chest down into the water while keeping your hips at the surface. This is the fundamental movement that drives the butterfly undulation.

Using AI Analysis for Butterfly Improvement

Butterfly is particularly well-suited to AI video analysis because the key errors — sinking hips, incorrect kick timing, head position — are all visible from a side-on camera angle. AI form analysis can identify the exact phase of your stroke where your hips drop and correlate it with your kick timing and head position.

SportsReflector's frame-by-frame analysis lets you see your body angle at each phase of the stroke, making it easy to identify whether your hip drop is caused by missed kick timing, incorrect head position, or insufficient chest press.

Summary

Fix sinking hips in butterfly by focusing on the wave undulation rather than power, timing your two kicks precisely with your arm entry and exit, and keeping your chin low during breathing. Use AI video analysis to identify the exact phase where your hips drop, and drill the dolphin kick on your back to build the correct movement pattern.