O2 — Breathing Trainer

Breathing Exercises & Calm

Free · In‑App Purchases · Designed for iPad. Not verified for macOS.

New: Holotropic Breathing — fast, deep connected breaths with hypnotic visuals for altered states. Plus CO₂/O₂ tables, box breathing and PB tests. 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.

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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

Version 1.12

The developer, Denis Tronin, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .

  • Data Not Collected

    The developer does not collect any data from this app.

    Privacy practices may vary, for example, based on the features you use or your age. Learn More

    Accessibility

    The developer has not yet indicated which accessibility features this app supports. Learn More

    Information

    Seller
    • Denis Tronin
    Size
    • 2.1 MB
    Category
    • Health & Fitness
    Compatibility
    Requires iOS 26.0 or later.
    • iPhone
      Requires iOS 26.0 or later.
    • iPad
      Requires iPadOS 26.0 or later.
    • Mac
      Requires macOS 26.0 or later and a Mac with Apple M1 chip or later.
    • Apple Vision
      Requires visionOS 26.0 or later.
    Languages
    English and 9 more
    • English, French, German, Indonesian, Japanese, Korean, Portuguese, Russian, Simplified Chinese, Spanish
    Age Rating
    9+
    In-App Purchases
    Yes
    Copyright
    • © TrueBloom Ltd.
  • Developer Website
  • Privacy Policy

    • Supports

    • Family Sharing

      Some in-app purchases and subscriptions may be shareable with your family group when Family Sharing is enabled. Learn More

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