Most health apps show today's steps and last night's sleep. CalmTide shows the cumulative biological outcome of those behaviours — your estimated baseline cortisol and HPA-axis balance — as a trend you can actually move over 8 to 12 weeks. Built entirely from Apple Health, on your device.
CalmTide reads the metrics your Apple Watch already collects, weighs them against published exercise-and-cortisol research, and turns them into a single weekly HPA Balance Score — plus a daily read on whether today's cortisol is likely low, moderate, elevated, or high.
HRV (SDNN) is the single best non-invasive proxy for HPA-axis state. CalmTide tracks your rolling average — every drop nudges your estimated cortisol load up.
Deep-sleep shortfall and REM disruption raise next-day cortisol. CalmTide reads your sleep stages and weights deep sleep most heavily.
Zone 2 lowers baseline cortisol; stacked Zone 4–5 sessions spike it. CalmTide classifies every workout and flags overtraining before it costs you.
As little as five minutes a day has a measurable cortisol effect. CalmTide credits logged mindful minutes and includes a guided breathwork timer.
Resting heart rate, respiratory rate, blood oxygen and VO₂ max round out the picture as secondary stress and recovery signals.
Morning light sharpens your Cortisol Awakening Response. Connect SolGlow and its sun & CAR data feed straight into your score.
Your live HPA Balance Score ring, one smart recommendation tailored to today's signals, and a five-item daily protocol checklist: breathwork, Zone 2 on track, 7+ hours sleep, no stacked hard sessions, and 15+ minutes of morning sun. A recovery-signals row shows HRV, resting HR, sleep and respiratory rate at a glance.
A MET-minutes progress bar against the research-backed 530/week target, a per-day zone-distribution chart, and a session list where every workout carries a cortisol-effect badge — reducing, neutral, or spiking — so you can see exactly which sessions helped and which cost you.
The headline view: an 8-week estimated baseline-cortisol line against an optimal target trajectory, with annotated spikes (that stacked-HIIT week shows up here) and milestone markers like "HRV improved" or "CAR score crossed 70." This is the anxiety-relevant signal most apps never show you.
Plus an Insights tab with HRV history, sleep-architecture breakdowns, a sun-to-next-day-HRV correlation, noise-exposure trends, and VO₂ max as a long-term HPA-health proxy.
SolGlow owns the sun: UV, vitamin D, and morning-light timing. CalmTide owns stress recovery: cortisol load and HPA-axis balance. Install both and they share a secure on-device container — no servers, no accounts — so each app gets smarter. Neither needs the other to work.
When SolGlow is connected, your morning-sun and CAR data feed CalmTide's weekly score, and a new "Sun → next-day HRV" correlation appears in Insights — so you can see, in your own data, whether getting out in the morning actually steadies your nervous system.
Your HPA score and today's recommendation on your wrist, synced from the phone.
A Today-summary widget and an HPA-ring widget keep your trend one glance away.
An 8am check-in, post-hard-workout recovery nudges, a Sunday weekly summary, and an alert when two hard sessions stack up.
Everything is computed on-device from Apple Health. No account, no analytics, and no health data ever leaves your phone.
CalmTide asks for the essentials on day one and requests deeper metrics only when you explore the features that use them.
Scores are clearly labelled as estimates from published research — not a clinical cortisol measurement. CalmTide tells you what it can and can't know.
CalmTide's scoring models are informed by published research on exercise, recovery, and the HPA axis — including the dose-response relationship between training volume and cortisol, and the measurable cortisol effects of sleep, breathwork, and morning light.
CalmTide provides wellness estimates based on published exercise-physiology research. It is not a medical device and should not be used to diagnose or treat any condition. Read the deep dive on the science behind CalmTide.