FLUX: Run to Your Heartbeat

Your heart becomes the DJ. FLUX is the first running app that reads your live heart rate and plays the perfect track from YOUR library to match it — in real time. The music reacts to your body. HOW IT WORKS - Connect Apple Music, and a Garmin, Polar, COROS, Whoop or any Bluetooth heart-rate strap. No sensor? Your phone tracks your cadence instead — same sync, zero gear. - FLUX tags every track in your library with a BPM and an Energy Score, sorted into your personal training zones. - FLUX works with the Apple Health app. It reads your resting heart rate, date of birth, biological sex, weight and height to personalise your heart-rate zones, and writes every completed workout back to Health. - Run. Your effort drives the zone, and FLUX crossfades into the matching track automatically — without you touching your phone. WHY FLUX IS DIFFERENT - Real-time, not average. Most apps pick an average tempo before you start. FLUX reacts to your heart rate as it changes, switching tracks as you push or ease off. - Your music, your library. Not someone else's playlist — the songs you already love, sorted by energy. - Personal zones. Heart-rate zones calculated from your own profile using the Karvonen formula. - Drop Sync. Mark where a track really kicks in, and FLUX starts it there — perfect for intervals. - Sync Score. After every run, see how locked-in your body was with the music, your winning track, splits and route. One number to chase and beat. - Build your own workouts, or let FLUX Lab build one for you with AI. FOR COACHES Build structured workouts and send them straight to your athletes. Coach Mode turns your training plan into a synced run. RUN SYNCED Whether you're chasing a 5K PR or grinding out marathon base miles, FLUX turns every run into a session where your body drives the sound. Requires an Apple Music subscription. Works with the Apple Health app. Works on iPhone.