Sauna Score: HRV & Sleep

**Did the sauna actually move your numbers?** You sit at 180°F three times a week and watch your HRV wander. Was that the sauna, or last night's dinner? Sauna Score answers that one question. It pulls your HRV, resting heart rate, and sleep from Apple Health and compares the weeks you hit your protocol with the weeks you missed. The Finnish longevity study ran the same comparison across 2,300 men for 20 years (Laukkanen, JAMA Internal Medicine 2015). Here, both groups are you. Works with whatever you already wear: Apple Watch, Garmin, Oura, Whoop. === Pick a protocol. We hold you to it. === Every study behind sauna's reputation measured how often people went. So you pick a cadence and the app tracks whether you keep it. Laukkanen — 4–7×/week, 20 min at 174°F. The longevity default. (JAMA Internal Medicine, 2015) Søberg contrast — 57 min hot + 11 min cold plunge per week, finish cold. (Cell Reports Medicine, 2021) Japanese totonou — the 3-set ritual, for the parasympathetic rebound Beginner ramp — three weeks to get you to Laukkanen === Results by the week === Once a week you get your HRV, resting heart rate, and sleep on target weeks next to off weeks, your eight-week trend, and where you sit against people your age and sex. The honest part: the Finnish numbers are observational, and the controlled trials since have been more guarded. We built the app knowing that. Every figure carries a confidence label (signal probable, below threshold, or needs more data), and when the evidence is thin the app tells you so instead of inventing a trend. === Daily heat readiness === One of three calls each morning: Go hot, Go gentle, or Skip. The call weighs your HRV against your typical week, last night's sleep, your resting heart rate, and the heat exposure you've already banked. There is no score out of 100 and no streak to protect. === Your wearable can't follow you in === A sauna runs 80–95°C. Most wearables are rated to about 35. Even one that survives won't tell you much in there: everyone's pulse races at 100°C, so a high reading just confirms the room is hot. So the app skips in-session readings on purpose. It reads your morning baseline before you go and your overnight recovery after. === End-of-session alarm === Your phone stays outside the cabin. When the timer hits zero it rings or vibrates, loud enough to reach you through the door. === A real sleep score from Apple Health === Every morning, a 0–100 read built from five inputs: Performance (duration), Efficiency (time awake), Restorative (Deep + REM), Bedtime (drift from your 7-night onset median), and Interruptions (awakenings). The targets come from AASM consensus (35% combined Deep + REM; 3–5 awakenings as the normal adult range), not numbers we made up. === Built for people who want receipts === iOS-first and native to Apple Health, so it works with the watch already on your wrist. Honest about what the data shows and what it doesn't.