Max Sauna

Turn your heart-rate recovery after a hot bath into a score with Apple Watch. PDF reports, recovery curves and more.

Max Sauna is your Apple Watch + iPhone companion for hot-bath wellness, turning the quiet "afterglow" into visible heart-rate data with HRR-based scoring.

■ Choose your hot phase

• Warming room (ondol) — default
• Hot spring (onsen)
• Hot bath / hot tub / jacuzzi
• Hot yoga
• Infrared sauna
• Mild steam bath
• Sauna
• Other / Custom

■ Two-phase or three-phase Default: Hot phase → Rest. Enable the three-phase flow in Settings: Hot phase → Cool-Down → Rest. Optional Warm-up and Extra phases can be added inside a set. Simple Mode runs continuously and detects sets from HR peaks.

■ Hands-free on Apple Watch Advance phases with Double Tap (Series 9 / Ultra 2+), Digital Crown, or screen tap.

■ Afterglow Score (HRR-based) A 0–100 score for how quickly your parasympathetic system reactivates, using heart-rate recovery at 1, 3, and 5 minutes. Per-set HRR is also shown.

■ Flow Quality Score A 0–100 score from heart-rate spikes during transitions.

■ Sleep Score (reference) A reference value computed from your Apple Health sleep data (duration, bedtime, interruptions). Separate from Apple's own Sleep Score.

■ Interactive heart-rate chart Tap for values, pinch to 20×, overlay 60-second and 10-minute moving averages.

■ History · Analysis · Venue Map Recovery slope, recovery curves, HRR trends, and multi-session comparison. The Venue Map gathers the facilities you've visited.

■ PDF report and CSV Export an A4 PDF report (3 pages) for any date range. Export and import your data as CSV.

■ Plank training (optional) Enable in Settings → Add-ons. Countdown (1–30 min) or count-up, with heart rate from Apple Watch.

■ Your data stays with you iCloud sync restores your history after reinstalling. Sessions also save to Apple Health as workouts.

■ Requirements

• iOS 18.0+ / watchOS 26.0+
• Apple Watch is required to record sessions; the iPhone app provides history, analysis, settings, and the plank timer.
• Double Tap: Series 9 / Ultra 2+

■ Important Not a medical device. All scores and heart-rate values are for reference only, not for diagnosis or treatment. Use hot baths at your own risk and consult a physician if you have health concerns. Avoid dehydration, dizziness, and heat-related illness.

Privacy: https://naokianraku.github.io/maxsauna-privacy.html