ZoneTrainer: Zone 2 HR Coach

Train smarter with ZoneTrainer — the dedicated heart rate zone training app built for runners, cyclists, and endurance athletes focusing on Zone 2 aerobic base building. 🎯 REAL-TIME ZONE TRACKING & COLOR CUES Connect any Bluetooth Low Energy (BLE) heart rate monitor and track your target zone (1–5) in real time. Dynamic UI feedback changes color instantly based on your intensity: • Teal: Inside target training zone • Amber: Outside target zone • Pulsing Ambient Ring: Real-time heart rate intensity visualizer 🔊 HANDS-FREE AUDIO ALERTS & DYNAMIC DUCKING Keep your phone in your pocket and train with your screen off: • Spoken voice announcements during zone transitions ("Entering Zone 2", "Returning to Zone 2") • Dynamic Audio Ducking — automatically lowers music and podcast volume during voice cues and smoothly restores it • Periodic audible feedback if your heart rate is too high or too low • Configurable alert intervals (15s, 30s, 60s) with Natural Human Voice and System TTS options ⏱️ SAMPLE-ACCURATE CADENCE METRONOME Master your running cadence and cycling rhythm: • Dedicated continuous AudioTrack PCM streaming engine • Ultra-precise timing (±0.02 ms) with zero audio lag or skipped beats at high tempos (up to 240 BPM) • Independent volume control and instant on-the-fly tempo adjustments 📊 5 PHYSIOLOGICAL ZONE CALCULATION FORMULAS Choose the exact formula that matches your physiology and athletic profile: • Karvonen (HRR): Factors resting heart rate and Heart Rate Reserve • Lactate Threshold (Friel LTHR): Endurance zones anchored to your 20–30 min threshold test • Tanaka Formula: Age-predicted formula optimized for masters and endurance athletes (208 - 0.7 × Age) • Gellish Formula: Linear regression formula for precise max HR estimation (207 - 0.7 × Age) • Standard Fox: Percentage of maximum heart rate (220 - Age) 🏃 PROGRESSIVE TRAINING PROGRAMS & CUSTOM BUILDER Pre-built aerobic workouts with structured warm-up, target zone, and cool-down intervals: • Aerobic Base Building (Zone 2) • 5K Training & Tempo Work • Marathon Prep & Endurance Volume • Custom Program Builder to design your own interval workouts 📈 WORKOUT HISTORY, TCX & CSV EXPORT Complete data portability with zero vendor lock-in: • TCX Export: Export workouts to standard Training Center XML compatible with Strava, Garmin Connect, and Intervals.icu • CSV Export: Single session and bulk workout history export directly to spreadsheets via Android Storage Access Framework • Full JSON Database Backup & Restore: Complete offline backup and migration for all workouts, custom programs, and intervals ⚙️ HARDWARE & SENSOR COMPATIBILITY Fully compatible with standard Bluetooth Low Energy (BLE) heart rate monitors broadcasting the GATT Heart Rate Service: • Polar: H10, H9, Verity Sense, OH1 • Garmin: HRM-Pro, HRM-Dual, HRM-Fit • Wahoo: TICKR, TICKR X • CooSpo, Magene, Scosche: Chest straps and optical armbands • Smart automatic reconnection with capped backoff to your last paired device 📱 ADVANCED ANDROID INTEGRATION • Persistent background foreground service with live lock screen telemetry (live BPM & Zone stats) • Picture-in-Picture (PiP) floating overlay • True AMOLED dark theme and battery-efficient layout • Full landscape orientation support for bike mounts and treadmills 🔒 100% PRIVATE, OFFLINE-FIRST & FREE • 100% free with no subscriptions, no paywalls, and no ads • No account creation, no sign-ups, and zero cloud dependencies • All biometric logs, workouts, and settings stay strictly on your device • Zero third-party tracking and zero analytics SDKs 📲 REQUIREMENTS • Android 8.0 (Oreo) or newer • Bluetooth Low Energy (BLE) compatible heart rate monitor