WHOOP charges $199/yr for a strap. I gave the same recovery score away free.
Hey PH. Short version of why Helix exists: I wanted a recovery score, every option came with hardware I didn't need, and my Apple Watch was already collecting the exact signals those straps collect.
So Helix reads Apple Health on-device and gives you one number every morning. It's built from overnight HRV, resting heart rate, respiratory rate, wrist temperature, SpO2 and last night's sleep, and every signal is scored against your own rolling 60-day baseline rather than against the average. Through the day it tracks strain against a ceiling that moves with how recovered you actually are. Green means push, red means back off. That's the whole loop, and it's free forever.
There's no server and no account. Every score is computed and stored on your iPhone. The AI coach calls out to OpenAI and Claude and only ever sends anonymized numbers.
But the part I actually want to talk about is the half nobody answers.
A recovery score tells you how hard to go. It never tells you where. So Helix maps every workout your Apple Watch records onto the muscles it actually loaded, weighted 0 to 1, with no logging from you.
Real vectors, straight out of the app:
Run: calves 0.80, quads 0.55, hamstrings 0.50, glutes 0.50, tibialis 0.40
Ride: quads 0.80, glutes 0.55, hamstrings 0.40, calves 0.30
Climb: forearms 0.80, upper back 0.60, biceps 0.55, abs 0.40
Jump Rope: calves 0.85, tibialis 0.45, forearms 0.35
XC Ski: eight muscle groups, because it genuinely is a whole-body sport
Golf: obliques 0.50, forearms 0.40, and honestly not much else
Three details I'm weirdly proud of:
The vector is only the shape. Magnitude comes from the session's TRIMP, so a casual jog and an all-out 10k load the same muscles in the same proportion at very different intensities.
Hills change the answer. If a run has elevation gain, calves and glutes get biased up by ascent. Around 250m of climbing is a properly hilly session and moves those two by up to 60%.
Fatigue decays on each muscle's own clock. Quads, glutes, hamstrings, chest and back take about 72 hours. Delts, arms, abs and adductors about 54. Forearms, calves and tibialis about 40. Train something before it clears and you watch the load stack instead of reset.
63 sports are mapped.
Now the comparison everyone's going to make anyway, so I'll make it myself.
WHOOP is a good product and their strain model is better documented than mine. But they measure overnight HRV, resting heart rate, skin temperature and sleep, and so does the watch on your wrist. The sensor stopped being the scarce thing when Apple shipped it to a few hundred million people. Interpretation is the scarce thing, and interpretation is software with no marginal cost. million people. Interpretation is the scarce thing, and interpretation is software with no marginal cost.
That changes what you're allowed to charge for. WHOOP has hardware to pay for, so the recovery score has to sit behind the membership. I have none, so the core loop is free. Where I think I'm genuinely ahead rather than just cheaper: a wrist score stops at the wrist. Helix also does per-muscle fatigue, uploaded blood panels scored for your age and sex, and VO2max testing with Cooper tests and race predictions. A strap will never see your ferritin and other markers supporting your cardiovascular recovery.
Where WHOOP still wins, honestly: it samples 24/7 from a device you never take off, and an Apple Watch spends an hour a day on a charger. Their raw data is denser. I'd rather say that than pretend otherwise.
Helix Pro is $9.99/mo or $59.99/yr for the deep end. The part that competes with a $199 membership is free.
Replies