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