# O2 — Breath Hold Apnea Trainer — Freediving, Breathwork & Sleep

> Freediving, Breathwork & Sleep (iPhone/iPad app by Denis Tronin.)

- Source: https://appshunter.io/ios/app/o2-breath-hold-apnea-trainer/id6757519007 (this page in markdown: same URL + `.md`)
- Developer: [Denis Tronin](https://appshunter.io/developer/1446210844)
- Category: Health & Fitness, Sports
- Price: Free with in-app purchases
- Age rating: 4+
- Requires: iOS 26.0 · 2 MB
- Languages: Russian, American English, Indonesian, European Spanish, Korean, German (Germany), Brazilian Portuguese, Chinese (Simplified, China), French (France), Japanese
- Released: 2026-01-12
- Data updated: 2026-09-04
- User reviews in markdown: https://appshunter.io/ios/app/o2-breath-hold-apnea-trainer/id6757519007/reviews.md

## What is O2?

Train your breath like a professional freediver.

O2 is a science-based breath-hold training app that helps you extend your breath-hold time, build CO₂ tolerance, and improve mental focus through progressive training protocols.

PROVEN TRAINING METHODS
• CO₂ Tables — Build carbon dioxide tolerance with decreasing rest intervals
• O₂ Tables — Extend breath-hold capacity with increasing hold times
• Box Breathing — The 4-4-4-4 technique for stress relief and focus
• Progressive difficulty levels from beginner to advanced

BUILT FOR PERFORMANCE
• Designed for freedivers, spearfishers, swimmers, surfers, and athletes
• Used by professionals to prepare for competition and improve underwater performance
• Backed by established breath-hold training science

SMART TRAINING EXPERIENCE
• Haptic feedback guides you through each phase without looking at the screen
• Voice cues announce hold and breathe phases
• Visual timer with clear phase indicators
• Track your progress with detailed statistics

HEALTH INTEGRATION
• Sync workouts to Apple Health
• Track your training consistency
• Monitor progress over time

SIMPLE & FOCUSED
• Clean, distraction-free interface
• No subscriptions — one-time purchase unlocks everything forever
• Works offline, anywhere
• Family Sharing supported

Whether you're training for freediving competitions, improving your surf hold-downs, or simply want to experience the mental clarity that comes with breath control — O2 gives you the tools to progress safely and effectively.

Start your breath-hold journey today.

## Pricing and in-app purchases

Base price: Free.

**One-time purchases**

| Purchase | Price | Type |
| --- | --- | --- |
| Lifetime Access | $9.99 | one-time |



## Version history (last 5 releases)

### 1.13 — 2026-09-01

Version 1.13

• Share your practice — a 6-second video card with your session stats and the breathing ring, ready for Instagram Stories, Reels, Facebook and X
• A new completion screen celebrates every finished session
• Bug fixes and performance improvements

### 1.12 — 2026-06-29

Version 1.12 — Introducing Holotropic Breathing!

• New guided practice: fast, deep connected breathing for altered states and emotional release
• Hypnotic full-spectrum visuals guide every breath
• Built-in safety screen — review contraindications before your first session
• Bug fixes and performance improvements

### 1.11 — 2026-05-31

Now available in more languages, with a calmer, faster experience and under-the-hood improvements. Breathe easy.

### 1.10 — 2026-05-31

NEW: Advanced O₂ Table — push past your limits with longer, elite-level breath-holds.

• Smart recalibration now tunes every table to your current level, so each session stays challenging but safe.
• Refined phase timing and smoother haptics.
• Stability improvements and bug fixes.

Thanks for breathing with us — keep training!

### 1.9 — 2026-05-21

Version 1.9 — Train harder, stay calibrated!

• New Advanced O₂ Table — our most demanding protocol yet, with long holds up to 90% of your personal best
• Smart recalibration — when a session feels too easy, O2 now suggests retaking your PB test so your tables keep matching your real level
• Retake your PB test anytime once you've completed every plan
• Bug fixes and performance improvements

## More apps by Denis Tronin

- [Safe Scanner](https://appshunter.io/ios/app/safe-scanner/id1509334364)
- [Work Remotely](https://appshunter.io/ios/app/work-remotely/id1620126090)
- [Loopix: Analog Film Camera](https://appshunter.io/ios/app/loopix-analog-film-camera/id6757521749)
- [UniBook — Read Without Limits](https://appshunter.io/ios/app/unibook-read-without-limits/id6757717595)
- [Rakoon: Gym Workout Tracker](https://appshunter.io/ios/app/rakoon-gym-workout-tracker/id6757954467)

All apps by Denis Tronin: https://appshunter.io/developer/1446210844

## Related topics

[o2 circuit training](https://appshunter.io/ios/topics/o2-circuit-training)

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-09-04.*