O2 - Breath Hold Trainer
Train your breath holds with science-based apnea tables
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Tronin Denis

O2 - Breath Hold Trainer - Train your breath holds with science-based apnea tables

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O2 brings professional freediver training to your pocket. Unlike generic breathing apps, it uses real CO₂ and O₂ apnea tables - the same methods used by competitive freedivers to safely extend breath holds Features: • Adaptive training based on your personal best • CO₂ tables (fixed holds, decreasing rest) • O₂ tables (progressive holds, fixed rest) • Box breathing and relaxation exercises • Progress, streaks and stats • HealthKit integration • Safety-first approach with guided warm-ups

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Tronin Denis
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Hey Product Hunt! 👋 I built O2 because I got into freediving and couldn't find a decent training app. Most "breathing apps" are just meditation timers — they don't understand apnea training. Real freedivers use CO₂ and O₂ tables: structured workouts that progressively train your body's tolerance. I learned this from dive instructors but had to use spreadsheets to track my sessions. That felt broken. So I built O2. It: - Tests your personal best safely - Generates training tables based on YOUR capacity - Tracks progress over time - Makes sure you warm up properly (safety first!) The foundation breathing exercises are free. Pro unlocks all the training tables. Would love feedback from any divers or breath-work enthusiasts here!