Ever wished you could race against yesterday's you? Sprint Run turns your past runs into AI-powered virtual opponents. We call it Shadow Running — pick any previous run, and our AI reconstructs it as a real-time pacemaker that guides you with voice feedback 1. Run once to create your baseline 2. Choose a difficulty — Average You, Recent Best, or Personal Best 3. Start running. Your AI Shadow runs alongside you with real-time audio cues: "You're 3 seconds ahead" or "Shadow is pulling away"

I built Sprint Run because I was tired of running alone with no motivation. Running apps track your data, but they don't make you feel anything. I wanted something that makes every run feel like a competition. The idea is simple: your best opponent is yourself. Shadow Running takes your real GPS data from past runs and reconstructs it as a live virtual pacer. When you hear "Shadow just passed you," something clicks — you push harder. ▎ Some things I'm proud of: ▎ - The run quality scoring algorithm took months to calibrate against real runner data ▎ - VO2max estimation uses the Jack Daniels formula with our own corrections ▎ - Peer comparison is based on RunRepeat's 2.3M runner dataset ▎ I'd love your feedback. What features would make you actually want to run more?

Sprint Run: AI Pacemaker

Race against your past self-AI creates a virtual shadow

Race against your past self-AI creates a virtual shadow