Riven turns your Apple Watch into a muscle failure tracker. It auto-detects your exercise, counts reps hands-free, and measures rep speed loss — the science-backed signal of true muscle fatigue — to tell you if you actually trained to failure or stopped reps short. Built for hypertrophy and strength training: no camera, no bar sensor, no extra hardware — just the watch you already own. Get a 0–100 failure score after every set, so every workout drives real muscle growth.