Open-source AI running coaching

Train together.
Race smarter.

AI coaching that running apps charge for, free and open source. Kestrel builds your plan and changes it day to day, syncs your watch, predicts your races, and keeps your whole team on one calendar.

Adaptive Training Plans

Plans by weekly mileage that move with how you feel, sleep, and race. Change a day by telling it you can't make it. Every change checked by fixed guardrails — no big jumps, no back-to-back hard days, week stays within 10%.

Six plan levels

Adaptive mileage

From 20 to 80+ miles per week. The AI coach moves days when you can't make them and eases off when readiness or soreness says so.

Guardrails built in

Safety first

No big jumps in volume. No back-to-back hard days. Every plan change respects your limits.

Fitness tracking

VO2max & zones

Race estimates from 100m to marathon with 80% ranges, pace zones, and fitness/fatigue/form scores.

Any AI, Open Models

Free built-in AI, your own API key (OpenAI, Anthropic, Gemini, OpenRouter, Groq), or a model on your laptop. Race predictions come from open models anyone can publish in Kestrel Lab.

Kestrel AI

Free default

Bring your own key

OpenAI · Anthropic · Gemini

OpenRouter, Groq, Ollama, LM Studio — keys stay in your browser, never sent to Kestrel's server.

Kestrel Lab

Open model hub

Browse, try, and publish open running models. Like Hugging Face for running AI.

Team Calendar

Anyone can start a school team: calendar, meets, RSVPs, availability, posts and team mileage. Names appear on the leaderboard only for athletes who choose to share.

Team management

Invite codes

Start a team for your school. Others join with an invite code or link. Owner manages the calendar.

Privacy by default

Health stays private

No coach view of training, teammates never see health, log, or contact details.

Watch sync

Intervals.icu

Garmin and COROS sync through intervals.icu. Each run gets difficulty from pace and heart rate.

Try It

🏭

Kestrel Lab

Browse, try, and publish open running models. Model cards, tags, API access.

📊

Race Predictor

Enter your recent times to predict your next race with 80% confidence intervals.

🤖

AI Coach

Chat about your plan, log, fitness, and next meet. Free default AI or your own key.

Start Your Free AI Coach Today

No paywall. No premium tier. Just advanced running analytics for everyone. Sign in with Google or create an account to get started.

About Kestrel

Kestrel was created to democratize high-tier fitness metrics and coaching features typically paywalled by platforms like Strava Premium. Our mission is to make advanced running analytics accessible to everyone — especially school teams with limited budgets.

Built as an open-source project, Kestrel gives you full control over your data, your models, and your coaching experience. Every feature that premium apps charge for is available here for free: from adaptive training plans and race predictions to AI-powered coaching and team management.

Whether you're a high school cross-country runner or a marathon trainee, Kestrel provides the insights you need to train smarter and race faster.

KESTREL

Kestrel Lab

Schedule

Team schedule

Posts

Reload and pick your name to post.

Events

Event type

Practice type

Availability

Notes

Training

Your training

Training plan

Fitness score

Your training load over the last 6 weeks, like Strava's Fitness & Freshness.

Race fitness

What you could race right now, from your races and PRs (HawksPredict). The small line under each time is its 80% range.

Race-day calculators

Heat and hills: what the weather costs your race

Enter the time you would run on a cool, flat day and the conditions. Uses the temperature + dew point chart behind the rest of Kestrel.

Race Cool-day time

Temperature °F Dew point °F Climb ft per mile

Taper: miles for the last weeks before a race

Race Peak week (miles) Longest run (miles, optional)

Runners like you: your marathon training next to real marathoners

Compares your last 16 weeks of watch runs with 14,000 real marathon runners. Add a goal time to see what runners at that time trained.

Goal marathon time (optional)

Training paces

Every workout in Kestrel uses these.

Based on

How it works

Every run is searched for races. Any run that covered a race distance (1600 to 10K) at race effort counts, whatever it was labelled, and if it beats a PR on file Kestrel updates the PR. The fastest stretches inside your runs (from your watch, through intervals.icu) count too.

Course and weather are taken out. Every race and hard run is credited back to a flat course on a cool day. Van Cortlandt runs about 5.5% slow (about a minute on an 18-minute 5K), other cross-country courses about 2.5% plus their hills, and heat by temperature plus dew point (about 1% at 120, 3% at 140, 6% at 160). Heart rate on steady runs is read the same way. Your PRs stay the real times, and a cross-country race counts toward your XC PR, never your track one.

HawksPredict reads your results. Your races and PRs from the last two years (a 5K you typed in only counts when nothing newer exists) go into HawksPredict-Lite, a small model trained on collegiate and Ontario high-school race results. It predicts a time for every event from 400 to the half marathon, with an 80% range, and learns your own speed-vs-endurance shape from the distances you have run. Your race VO2max (the oxygen use your times are worth) is read off its 1600, 3200 and 5K times and sets your training zones.

It uses your best results. It looks at your fastest result at each distance from the last two years, so someone coming back from a layoff or injury will read faster than they are today; add a recent race or edit the PR date when that is you.

Garmin's VO2max is matched to your races. Garmin estimates VO2max from heart rate vs speed, which usually reads higher than race results. Kestrel finds your personal ratio from races run near a Garmin reading, so the number can track your fitness between races.

Runs without a race. If you have no race or PR at all, Kestrel falls back to a training estimate from rep sessions and heart rate on steady runs, and says so.

More events, your choice. Tap Edit on Race fitness to show 100m, 200m, 600m, 1000m or the steeplechases. HawksPredict-Short estimates them from your other times (and any PR you enter at those distances), using the relationships between events in World Athletics, collegiate and Ontario high-school results. Every row shows how sure it is: the dot and the ± are the width of its 80% range. Sprints and steeples are the least certain: the model learned them mostly from elite athletes, with a check on real high-school sprinters.

Marathon, from your training. Tap Edit and turn on Marathon. HawksPredict-Marathon reads your last 16 weeks of watch runs (weekly miles, long runs, pace, your best 5 to 15 mile effort) and needs at least 15 running days. It was trained on 14,000 real marathon days with their training logs; on runners it had never seen it was off by about 6% on average, and its range is about ±10%, so treat it as a ballpark. It does not use your PRs, and it does not know the course, weather or taper.

Mileage matters for long races. 10K and half marathon estimates slow down when your last 4 weeks are low on miles.

VO2max is your watch's (Garmin or COROS) when it sends one. Kestrel VO2max is what your race times are worth, and it sets your training paces. With no watch number, the headline is Kestrel' heart-rate estimate from steady runs (using your resting heart rate when known). Watches tend to read high for some runners; none of these is a lab test.

Fitness score is your training load (minutes x effort) averaged over 42 days; fatigue is the same over 7 days, and form is fitness minus fatigue. It goes up with steady training and doesn't depend on racing.

You

Profile

Name (teammates see this) Colour on the calendar Grade Sex (race models use it if you give it) Show my weekly miles on my teams' mileage boards

Teammates see your name, colour, availability and RSVPs. Your training, health and body map are only yours (and your AI coach's).

Personal records

These anchor your Fitness States, so add the date if you know it: recent PRs count more.

Reload and pick your name to add your PRs.

Kestrel AI

Race models

Account

Or set up your watch yourself

About 5 minutes, once. After that your runs, splits and Fitness States update on their own every time you open Kestrel.

1

Make a free intervals.icu account
intervals.icu is a free training site. It's the bridge between your watch and Kestrel: Garmin and COROS send runs to it officially, and Kestrel reads them from there.
Open intervals.icu
2

Connect your watch there
On intervals.icu go to Settings → Connections and connect Garmin (or COROS). Then use the option on that connection to import your old activities, so your full history comes across, not just new runs.

Don't connect Strava there instead: Strava doesn't let intervals.icu share your runs, so Kestrel can't see them.
3

Copy your athlete id and API key
Still in intervals.icu Settings: your athlete id is under your name (looks like i12345). Scroll to Developer Settings for the API key.

Athlete id API key

Send your plan to your watch
Sends the next 14 days of your plan to intervals.icu as workouts with your own paces. Garmin and COROS pick them up from there once "upload planned workouts" is on in intervals.icu (Settings, Connections). Sending again updates the same workouts.
4

Import your full history
Kestrel pulls everything intervals.icu has, a few months at a time. It keeps going in the background, so you can leave this page.
5

Add your PRs
PRs anchor your Fitness States until your watch has enough races. Add the date if you remember it.

Train together.Race smarter.

Adaptive Training Plans

Six plan levels

Guardrails built in

Fitness tracking

Any AI, Open Models

Kestrel AI

Bring your own key

Kestrel Lab

Team Calendar

Team management

Privacy by default

Watch sync

Try It

Kestrel Lab

Race Predictor

AI Coach

Start Your Free AI Coach Today

About Kestrel

Team schedule

Your training

Team mileage

You

Train together.
Race smarter.