Negative Split for Strava

Free, local training analytics on your own Strava runs: rTSS, GAP, zones, age-graded PBs, VDOT, a shareable Run Card. No upload.

🏃 Strava shows you the run. Negative Split explains it: right on your own activity, profile and training pages, computed entirely in your browser. It adds the deep, honest analytics that usually sit behind Premium (or nowhere), and it never uploads a thing. ✨ No login, no subscription, nothing leaves your browser. 📊 ON EACH ACTIVITY • Negative-split pacing: did you finish faster than you started, split into two halves. • rTSS, Intensity Factor & Normalized Graded Pace (GAP, Minetti model): real training load, hill-fair. • Aerobic decoupling (Pa:HR): did your pace-per-heartbeat drift. • Time in zone + the 80/20 read: how easy vs hard the run really was. • Auto interval detection: finds your reps (warm-up & recovery excluded) and lists each one. • Fitness / Fatigue / Form (CTL/ATL/TSB) trend + training monotony. • Injury-risk read: Acute:Chronic Workload Ratio with the sweet-spot band. • Aerobic trend: Efficiency Factor & decoupling across your recent runs. 🖼️ A SHAREABLE RUN CARD • Turn any run into a clean, downloadable card: your route silhouette, the headline stats, your interval reps as a bar chart, your heart-rate zones and a playful one-liner about the run. Save it and add it as a photo to your Strava activity. • Built in your browser from your own run: nothing is uploaded, and there is no Strava branding on it. 🏅 ON YOUR PROFILE • A clean, sortable personal-best list with Riegel-equivalent scoring (which PB is actually your strongest). • Age-graded PBs: how your bests rank against the age & sex record standard (official WMA/Jones 2025 road tables), with class bands (world / national / regional / local) and a shareable "Age Grade 82.4% · National Class" line. • VDOT: a performance-based VO2max estimate (Daniels/Gilbert) from your best race, on the same scale Garmin reports, computed from a real effort rather than wrist heart-rate. • Race predictions for 5K/10K/Half/Marathon, fitted to your own PB curve: honest about the marathon. • Pace-duration curve + Critical Velocity (CV) and D′. 🏠 ON YOUR DASHBOARD • Fitness / Fatigue / Form, right in your profile card: today's numbers, a form pill (fresh / neutral / productive / overreaching) and a fitness sparkline, plus your VDOT and age-grade score at a glance. The paywalled Fitness & Freshness read, free, where your day starts. • Kudos that feel good: a tiny thumbs-up confetti when you give kudos, and an orange outline on activities you've already kudoed, so you never double-check. No automation, ever: it only reacts to your own clicks. 🗓️ A FREE YEAR IN SPORT · WITH A HOLO YEAR CARD • A private, local recap: totals, sport split, a daily-activity heatmap, monthly volume and season bests, with a downloadable share card. Built from your own history, nothing uploaded. • Honest fun stats: cheeseburgers burned, Everests climbed, the walk to Mordor, episodes of doomscroll outrun: every number a transparent estimate with its formula one hover away. • Your runner archetype ("The Dawn Metronome", "The Weekend Volcano"…) on a holographic, illustrated trading card: tilt it, admire the foil, download it as a share image. ✍️ WHEN YOU EDIT A RUN • A suggested title and description from the detected workout (e.g. "6x6' @4:12→4:00"): copy it if you like it; it never changes your fields. • A playful alternative title too, the same one-liner your Run Card shows, one click to copy. 🔒 HONEST BY DESIGN ✅ 100% in your browser: your activity data is never uploaded, never sent anywhere. ✅ No login, no account, no subscription. ✅ No official Strava API, no AI on your data: every number is transparent, deterministic sports-science math. ✅ One named site permission (strava.com), never broad web access. ℹ️ Negative Split is an independent project. It is not affiliated with, endorsed by, or sponsored by Strava, Inc. Strava is a trademark of Strava, Inc. 🗞️ As featured on the5krunner: https://the5krunner.com/2026/07/13/negative-split-strava/ 📈 By Ownward: honest, local-first browser tools. https://ownward.hu