I built a free running plan generator that adapts when life gets in the way

arc.acqru.ai — free, no signup, no ads, no app store. Works in your phone's browser. I'm not trying to offer any personal coaching - just a tool for people to use.

Why I built it

Every training plan I've used had the same failure mode: it's a static PDF that assumes a perfect life. Miss a week for travel, illness, or a brutal work stretch, and you're left guessing — do I make it up? skip ahead? start over? The plan doesn't know anything happened.

ARC recalculates. Tell it "I can't run Thursday" or "this week wrecked me," and the remaining weeks reshape around it. Missed runs are treated as logistics, not moral failures. Nothing carries over, there's no make-up debt, and the plan heals itself.

What it actually does

Builds a plan from 8 real coaching systems — Pfitzinger, Hansons, Daniels, 80/20, Lydiard, Higdon, Maffetone, FIRST. It recommends one based on your profile and goal, and it won't suggest a method for a race distance that method's book doesn't cover.

Tells you the truth about your goal. Before it builds anything, a "Reality Check" runs your goal against your current fitness, your timeline, and how many days a week you can actually run. If the math doesn't work, it says so and shows you which levers do work (later race, different goal, more days). It will not flatter you.

Every pace is anchored to a real result of yours. Give it one recent race or hard effort — any distance — and every prescribed pace derives from that, not from a generic table.

Heat-aware. Enter the conditions and it adjusts prescribed paces and the training load credit. Same run costs more at 90°F and 75% humidity, and the model knows it. (I'm in Houston. This was not optional.)

Fitness / fatigue / form tracking (the standard Banister/PMC model) with a projected race time that updates as you log runs.

Goal-pace practice built into long runs in the late build weeks, for the methods whose books actually do that — so you're not arriving at race day having never held goal pace on tired legs.

How to use it

Open arc.acqru.ai on your phone. Add to Home Screen if you want it to feel like an app.

Fill in Runner Profile: runs per week, typical run distance, longest recent run, which days you can run — and one recent race result. That last one matters most; without it the paces are estimates.

Set your goal (a race distance and date, a time goal, or just "get consistent"), pick a coaching style or take the recommended one, and read the Reality Check before you build.

Day to day: the Now tab shows today's run — tap the card to log it. Log minutes, distance, conditions, how it felt, and any pain. Takes about fifteen seconds.

When life happens: the weekly check-in on the Now tab. Tap the days that won't work, set your energy level. The week rearranges instantly and it's all reversible.

Plan tab has your calendar (grid or week-block view) plus a "Your plan, explained" card that describes what you're building and why each run type exists. Progress has your fitness curve.

Honest caveats

It's a beta. I'm actively fixing things. There's a build number in the footer — include it if you report something.

Your data lives on your device only. No account, no server, nobody sees your training including me. The flip side: clear your browser data and it's gone. There's a one-tap export/import backup — use it.

Manual logging for now. Garmin/Strava/Apple Health sync is planned, not built.

Not medical advice. It's a training tool for healthy adults. The underlying model is established sports science, but the specific thresholds are still being reviewed by a sports-medicine physician. If something hurts, the doctor beats the app.

Free, and staying free for this group. I'm not collecting emails and there's nothing to buy.

What I want from you

Break it. Especially:

Tell me where the math looks wrong. Several real bugs got fixed this week because runners did the arithmetic by hand and caught the app overstating mileage on interval days.

Tell me where the coaching advice is off. If you're a coach or a serious runner and something contradicts what you know, I want to hear it — with the reasoning.

Tell me where it's confusing or says too much. It's been accused of over-explaining and I'm still cutting.

Mods - I'm not selling anything, just sharing with the sub as I've been using it and it's been a great tool. I'm certain others will find it valuable. Delete it if you must.