Bilateral breathing is a freestyle swimming technique where you alternate which side you breathe on, typically by taking a breath every three strokes instead of every two. This means you breathe to your right on one cycle, then to your left on the next, distributing your breathing equally between both sides. It’s one of the most debated habits in swimming, with strong opinions on whether every swimmer should adopt it or whether it’s just a useful tool to pull out when needed.
How It Differs From Unilateral Breathing
Most swimmers naturally develop a preferred breathing side. If you breathe every two strokes, you’re always turning your head to the same side. That’s unilateral breathing, and it’s the default for the majority of recreational and competitive swimmers. Bilateral breathing changes the count to an odd number, usually three or five strokes between breaths, so the breathing side alternates automatically.
There’s also a less common variation: breathing to one side for an entire pool length, then switching to the other side on the way back. This still counts as bilateral breathing because both sides get work over the course of a session, even though you’re not switching within each lap. Coaches sometimes recommend this approach as a stepping stone for swimmers who find every-three-stroke breathing uncomfortable.
Why Coaches Emphasize It
The biggest reason coaches push bilateral breathing is stroke symmetry. When you only breathe to one side, your body tends to roll more toward that side with every breath. Research on hip rotation in freestyle swimmers confirms that unilateral breathing creates a measurable roll asymmetry, where the body rotates further toward the breathing side and snaps back faster to the non-breathing side. Over thousands of strokes per workout, that lopsided rotation can shorten your stroke on one side and reduce overall efficiency.
Elite swim coaches recognize balanced body roll as a key factor in optimizing stroke length. Bilateral breathing is one of the primary tools they use to prevent those asymmetries from becoming ingrained. A study published in Sensors found that bilateral breathing did successfully reduce the degree of roll asymmetry compared to unilateral breathing, though it didn’t eliminate all differences between sides. Interestingly, using a snorkel (which removes breathing from the equation entirely) was the only condition that fully equalized rotation on both sides.
Shoulder Health and Injury Prevention
Freestyle puts your shoulders through nearly constant repetitive motion in the same direction. Over time, this can overdevelop the muscles in the front of the shoulder while leaving the muscles in the back relatively weak. That imbalance is a recipe for labral tears, rotator cuff problems, and internal shoulder impingement.
Bilateral breathing doesn’t fix this on its own, but it helps. By evening out your body rotation, you distribute the load more symmetrically across both shoulders. Swimmers who always breathe to one side tend to reach and pull slightly differently on each arm, which compounds the repetitive stress on the dominant side. Mixing in bilateral breathing, along with training other strokes, is one of the more practical ways to keep your shoulders balanced over the long term.
The Oxygen Trade-Off
Here’s where bilateral breathing gets controversial. Breathing every three strokes means you get roughly 33% fewer breaths than breathing every two strokes. That’s a real physiological cost. Your muscles depend on oxygen to produce energy and clear lactate from the blood, and limiting your air intake can leave you short during hard efforts.
For easy and moderate swimming, the reduced oxygen supply is manageable for most trained swimmers. But during race-pace efforts or high-intensity intervals, breathing every second stroke delivers the most oxygen when demand is highest. This is why you’ll rarely see sprinters using bilateral breathing in a 50- or 100-meter race. The performance cost of fewer breaths outweighs the symmetry benefits when every fraction of a second matters.
For distance swimmers and triathletes, the calculation is more nuanced. Some athletes use bilateral breathing during training to build symmetry, then switch to unilateral breathing on their stronger side during races. Others use a pattern of breathing every three strokes at moderate paces and drop to every two when the intensity climbs. There’s no single right answer, and personal comfort plays a significant role.
Open Water Advantages
Bilateral breathing becomes especially valuable outside the pool. In open water, conditions change constantly. Waves, wind, and chop can make it miserable or even dangerous to breathe into the weather. If you can only breathe to your left and the wind is driving water into your face from that side, you’re stuck. A swimmer comfortable breathing to both sides simply switches and keeps moving.
Visibility matters too. Pool and open water competitors need to see both sides of the course to track other swimmers, spot buoys, and navigate. Being able to sight to either side without disrupting your stroke gives you a tactical edge, especially in crowded triathlon swim starts or pack swimming situations. U.S. Masters Swimming specifically recommends developing this skill in the pool first so it feels natural when you need it in open water.
How to Start Breathing Bilaterally
If you’ve spent years breathing to one side, switching to bilateral breathing will feel awkward at first. Your non-preferred side will likely feel uncoordinated, and you may swallow water a few times. That’s normal. The key is to introduce it gradually rather than forcing yourself to do every lap on a three-stroke pattern from day one.
Start by dedicating your warm-up or cool-down to bilateral breathing, when the pace is easy and oxygen demand is low. This gives you time to focus on the mechanics without gasping. Another approach is to breathe to your non-preferred side for entire lengths, building comfort on that side before combining both into an alternating pattern. You can also use every-five-stroke breathing during drill sets to extend the challenge once every-three feels comfortable.
Even if you ultimately decide to race with unilateral breathing, practicing the opposite side regularly during workouts has clear value. It builds symmetry in your stroke, keeps your shoulders more balanced, and gives you a backup option when conditions demand it. Think of it less as a rigid rule and more as a skill worth having in your toolkit.