PACER · AI Running Coach
A coach for every kilometer you run. Your condition changes — so does your plan.
PACER is an AI-native running coach — an AI agent that makes its own decisions, not a chatbot wrapper. It reads training data you authorize directly from COROS or Polar, or through intervals.icu, and builds on Jack Daniels' VDOT, Hansons cumulative fatigue and 80/20 polarized training to craft — and continuously adapt — a training plan for your next race. Your device-platform account passwords are not stored.
A three-layer scientific decision model
Training advice combines real training data and sports-science calculations. Adjust plans through conversation and weekly reviews.
- Multi-dimensional state sensing: reads body and environment signals — COROS data sync, temperature and environment adjustments, sleep and HRV recovery monitoring.
- Core computation engines: decisions made with sports-science models — Daniels VDOT pace assessment, Banister TRIMP fatigue quantification, runner injury-medicine risk alerts.
- Dynamic plan output: executable daily training — weekly adaptive plans, pre-race taper, precise hydration and nutrition guidance.
Why PACER is an AI agent, not a chatbot wrapper
PACER wraps the LLM in a self-built core — a scheduling orchestrator, a rules/numeric engine and a knowledge base — that makes it a disciplined coach:
- Scheduling orchestrator (safety rails): say "I want to run more this week" and it won't just pile on volume — anything beyond what your body can absorb is clamped back to science-based limits, and plan changes only take effect after you confirm.
- Rules/numeric engine: pace, training load and hydration start from sports-formula reference values and constraints computed in code; the AI composes the plan and explains adjustments within them.
- Knowledge base (RAG, answers with sources): whether you can run with Achilles pain, how to carb-load before a race — answers are grounded in sports-medicine and nutrition literature, not generated out of thin air.
- Long/short-term memory engine: remembers your old injuries, preferences and goals, distills patterns you haven't noticed (late-run fade on long runs, mid-week dips) and speaks up at the right moment — it gets to know you better the more you use it.
Core capabilities
- Official COROS sign-in, training data sync and workout push, Garmin (via intervals.icu) and Polar data sync; data access and plan delivery depend on the connected platform and device
- AI-generated personalized race training plans for 5K / 10K / half marathon / full marathon
- Daniels VDOT fitness assessment with E / M / T / I / R five-zone science-based pacing
- Training reviews, in-depth pre-race analysis and finish-time prediction
- Conversational AI agent copilot (orchestrator safety rails + rules-engine reference constraints + knowledge-base RAG + long/short-term memory), for questions and adjustments anytime
- The three-layer decision logic is open-sourced as a Skill — plug it into Claude, Cursor or other MCP/Skill-capable tools yourself
FAQ
What account system does PACER use?
Email account system with verification/password setup. Decoupled from watch data sources, supports multiple devices.
What is PACER?
An AI-native running coach built by a marathoner and independent developer, powered by a proprietary orchestrator and kinematics engine.
How is PACER different from a regular running app, or a ChatGPT wrapper?
PACER combines training data, pace and load calculations, a training knowledge base and runner preferences to support plan generation, conversational adjustments, weekly reviews and pre-run and post-run advice. Syncing updates training data; plans can be adjusted in conversation or after weekly reviews, rather than being rebuilt after every sync. Consider your actual physical condition when following advice. Improved performance and injury prevention are not guaranteed.
Which devices and data sources are supported?
Official COROS MCP direct connection: training data read supported (about 24 months), workout push supported (server-side delivery); Polar via official authorized direct connection: training data read supported; workout write-back not supported (vendor does not accept third-party workouts); Garmin via intervals.icu relay: activity sync supported, structured workout push supported; other brands connect via an intervals.icu relay; reading and workout-push support depend on intervals.icu's actual per-platform/per-device capabilities and device conditions (the membership page lists Garmin, COROS, Suunto, Wahoo and Zwift as conditional examples). Your account password is never stored; the WeChat mini program is currently not supported.
What training science is PACER built on?
Daniels VDOT (E/M/T/I/R pace zones), Hansons cumulative fatigue, 80/20 polarized training, and Banister TRIMP fatigue quantification.
Does PACER cost anything?
New users get a free trial covering VDOT assessment and plan generation (trial length subject to the actual in-app rules); an advanced membership follows. As of 2026-11-03 the membership page shows ¥99/year (the crossed-out ¥199/year is a comparison display, not a verified historical price); no auto-renewal; within 7 days of payment a refund is available minus a 1% payment-channel fee. Figures reflect the membership page display and are subject to the latest in-app terms and the Membership Service Agreement.
What can I use after my trial or membership expires?
You can still view existing plans and training records, manually sync data, export plans and read previously generated weekly reviews. AI coach chat, new plans and adjustments, new reviews and training advice, plan delivery through supported channels and proactive email reminders require an active trial or membership.
How do I get started?
Register or sign in with email at run2ai.cn, then connect a supported data source. PACER is a Web app available in a phone or desktop browser.
Can I run this model in my own AI tools?
Use the open-source ai-running-coach Skill in compatible MCP/Skill tools with your own model, data authorization and runtime. Its features, integrations, costs and generated results may differ from the hosted PACER service.
How does PACER protect my data?
Data comes from sources you authorize: official COROS MCP, official Polar authorization, or intervals.icu for other supported devices. PACER does not store device-platform passwords. Missing data limits advice; AI can be wrong and injury advice does not replace medical diagnosis.
Further reading: Training methodology (Daniels / Hansons / 80-20) · FAQ
Start with PACER for your next race →
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