Helix is a fitness intelligence app for iPhone and Apple Watch. It reads the health data your devices already record, scores how recovered you are every morning, tracks strain against a personal ceiling through the day, and turns sleep, heart data, workouts and bloodwork into one clear daily verdict: push, or back off.
Three things make it different, and they shape everything in these docs:
- You vs. you. Every score is measured against your own rolling baselines, never population averages. That is also why Helix needs a short calibration period before it speaks with full confidence.
- No backend, no account. Scores are computed and stored on your iPhone. There is nothing to sign up for and no server holding your health data.
- Honest numbers. Estimates are labeled as estimates. Missing data shows as missing, not as an invented number.
Start here
What’s free and what’s Pro
The core loop is free forever, with no account and no trial clock: recovery, strain, sleep and stress. Helix Pro adds the deeper labs.
| Area | Plan | What it does |
|---|---|---|
| Recovery, Strain, Sleep, Stress | Free | The daily loop: score, ceiling, verdict |
| VO₂max Lab | Pro | Trajectory, Cooper test, intervals, threshold, race predictions |
| Training Lab | Pro | Per-muscle recovery, strength index, logging, templates |
| Bloodwork & Experiments | Pro | Panel uploads, marker scoring, guided protocols |
| Energy Schedule & AI coach | Pro | Circadian energy curve; a coach that reads your numbers |
How these docs are written
We describe what each feature reads, how it personalizes to you, and which direction moves the number. We do not publish the internal math. Where a claim depends on your own data, the app itself is the source of truth; the docs tell you where to look.