Bilateral vs Unilateral Breathing in Swimming: Which Is Better for Triathletes? (2026)
Should you breathe every 2, 3, or 4 strokes? The honest answer for triathletes, with drills to fix lopsided strokes and breathe both sides comfortably.
By Lotte
Bilateral breathing (every 3 strokes, alternating sides) is the standard swim-coach advice. But for triathletes racing in open water, unilateral breathing (every 2 strokes, one side) is often *better* — as long as you can switch when needed. Here's the nuance most beginners miss.
Key takeaways
- 1Bilateral breathing builds a balanced, symmetrical stroke — train it
- 2Unilateral breathing delivers more oxygen — race with it most of the time
- 3Open-water swimmers MUST be able to breathe on both sides for sun, chop, and crowds
- 4The best pattern: bilateral in training, unilateral when racing hard
- 5Drills to switch sides take 4–6 weeks of consistent practice
In this article
Quick answer
In training: breathe bilaterally (every 3 strokes, alternating sides). Builds a balanced stroke and ambidextrous comfort.
In racing: breathe unilaterally (every 2 strokes, dominant side) most of the time. You get 50% more oxygen.
But: you must be able to switch to your weaker side instantly. Sun in your eyes, chop slapping your face, another swimmer crowding you — these all force a side-switch in open water.
For open-water skills generally see open-water swimming sighting.
Why coaches teach bilateral
Breathing only one side creates asymmetry over time: the breathing-side arm pulls shorter, the non-breathing arm crosses centerline, hips rotate unevenly. The result is a 'banana' stroke that pulls you off course in open water.
Bilateral breathing forces symmetric rotation — both hips roll the same amount, both arms pull the same length. Even if you race breathing every 2, you should train breathing every 3.
Why unilateral is faster in a race
Breathing every 3 strokes means a breath every ~3 seconds. Every 2 strokes means a breath every ~2 seconds. At threshold effort, that extra oxygen matters.
Most elite triathletes race unilaterally — or use a pattern like '2-2-2-3' (three breaths to one side, switch).
Unless you specifically enjoy bilateral or it keeps your stroke straighter, race on your dominant side.
Why open-water swimmers need both sides
In a pool, the conditions never change. In open water, you'll meet:
- Sun on one side at the turn — you literally cannot see to sight
- Wind chop slapping your breathing side — you'll inhale water
- Another swimmer crowding you — elbows in the face
- A buoy on your weak side — you need to spot it
Being locked to one side means you either swallow water, lose your line, or get spooked. Train the weak side until it's at least serviceable.
For wave-handling specifically, see open-water swimming for beginners.
Drills to learn bilateral breathing
Week 1–2: 3-3-3 drill. 25 m breathing every 3, 25 m every 5, 25 m every 7. Builds CO₂ tolerance and forces both sides.
Week 2–3: Kickboard side-breathing. 4 × 25 m holding a kickboard, breathing only to your weak side. Brutal at first, normal by week 3.
Week 3–4: 'Hypoxic' sets. 4 × 100 m breathing every 5 strokes. Trains lungs and stroke economy.
Week 4–6: Race-pace bilateral. 8 × 100 m at race pace, every 3. If you can hold this comfortably, you've nailed it.
More swim progression in structured swim training for triathletes.
The hybrid pattern most triathletes actually use
After a few seasons, most triathletes settle on a flexible pattern:
- First 100 m of a race: every 2 strokes, one side, to manage breathing in the chaos
- Settled into a rhythm: alternating sides every 50–100 m to keep balance
- Sighting strokes: breath comes naturally on the sight-side
- Last 200 m: every 2 on the dominant side to maximize O₂
Don't lock yourself into one rule. Train both, race the one that's working that day.
Breathing pattern comparison
| Pattern | Breaths/min | Best for | Trade-off |
|---|---|---|---|
| Every 2 (unilateral) | ~30 | Racing hard, finishing fast | Asymmetric stroke if used always |
| Every 3 (bilateral) | ~20 | Training, building symmetry | Less oxygen at high effort |
| Every 4 | ~15 | Sprints, finishing kicks | Only sustainable short distances |
| 2-2-2-3 hybrid | ~25 | Open-water racing | Takes practice to feel natural |
Frequently asked questions
Is it bad to only breathe to one side?
Not bad — but it creates asymmetry over time. Even if you race unilaterally, train bilaterally to keep the stroke balanced.
How long does it take to learn breathing on the weak side?
Most swimmers feel comfortable after 4–6 weeks of dedicated drills (2–3 swim sessions per week).
Should I breathe every 2 or every 3 in an Ironman swim?
Every 3 (bilateral) is recommended for long swims — the lower effort means oxygen isn't the bottleneck, and stroke symmetry keeps you straight.
Why do I get dizzy breathing bilaterally?
Usually CO₂ buildup, not oxygen lack. Build tolerance gradually with hypoxic sets. If it persists, see a doctor — could be sinus or ear-related.