Kiuas

Sauna · Cold · Rest

Sauna, cold, rest.
Round by round.

Kiuas tracks contrast therapy on your Apple Watch: the phase you’re in, the time left, your heart rate live, and calm alerts when it climbs too high. Each session becomes one workout in Health.

Coming soon to the App Store

iPhone with iOS 17 or later · Apple Watch with watchOS 10 or later recommended

The Kiuas dial: round 2 of 3, 8 minutes 42 seconds left of a 12-minute sauna.ROUND 2/308:42LEFT · OF 12:00

What it does

A small instrument for the sauna

  1. 01 Apple Watch

    Live session on your wrist

    A dial with the time left, the round and your heart rate. A tap on the wrist ten seconds before each change, Water Lock one tap away. If the app closes or the Watch restarts, the session picks up again or is saved later: it doesn’t get lost.

  2. 02 Protocols

    A plan, or a free session

    Start from Classic Finnish, Short contrast, First steps or Sauna only, or build your own rounds. Or go free: choose each phase as you go (sauna, steam room, cold shower, cold plunge, lake, snow, rest) with a goal you can change while you’re in.

  3. 03 Safety

    Alerts that say what to do

    A caution when your heart rate goes above your limit or recovers slowly after the cold. A stop when it stays high. Your limit comes from your age, is lowered when you log alcohol or caffeine, and can take heart-rate-lowering medicines into account.

  4. 04 Calories

    Kcal, estimated honestly

    In the heat your heart rate rises, but your energy use barely does. Kiuas estimates calories with a model built on published sauna and cold studies and always shows a range. You choose whether Health gets the Kiuas estimate or Apple’s.

  5. 05 Heat dose

    Minutes in the heat, days per week

    The minutes of Finnish sauna in each session and the sauna days in the last 7, the two numbers the long-term Finnish studies look at. Sources are linked in the app.

  6. 06 History

    History, corrections, export

    Every session on your iPhone: max, average and recovery per round, the heart rate chart with your limit, the alerts. Forgot to switch phase? Move the end, change a phase, drop a round. Export kcal by phase as CSV.

  7. 07 Health

    One workout in Health

    Each session is saved as a single workout with a part for each phase, heart rate and energy included, so it shows up in Fitness and its calories count toward your Move ring.

  8. 08 iPhone

    Timer only, without a Watch

    No Watch with you? The iPhone runs the same protocol as a timer, with notifications and a Live Activity on the Lock Screen and in the Dynamic Island. No heart rate, so no alerts.

Screens

Made to read at a glance, in the heat

Condensed numbers, one color per phase, nothing that moves when you lower your wrist.

Apple Watch

  • Apple Watch during a sauna phase: 08:42 left on the dial, heart rate 128.
    Sauna · time left
  • Apple Watch in a sauna with no set time: 06:18 elapsed, heart rate 146 shown in yellow, close to the limit.
    No set time · near the limit
  • Apple Watch during the rest phase: 12:50 on the dial, heart rate 96.
    Rest · recovery
  • Apple Watch in a free session asking What now?, with cold shower suggested after 13 minutes of steam room.
    Free session · what now?

iPhone

  • iPhone timer in the sauna phase: round 2 of 3, 08:42 left of 12:00, buttons To the cold, Pause and End.
    iPhone timer
  • Session summary: Classic Finnish, 3 rounds, max 159, average 115, recovery −23, heart rate chart with the limit at 158 and one alert.
    Session summary
  • History in light mode: five sessions in October with rounds, duration and maximum heart rate.
    History
  • Choosing a session: free session, First steps, Classic Finnish and Short contrast, with the button Start on Watch.
    Protocols

Safety

Two levels, no alarms

Kiuas watches your heart rate during the session and speaks only when there’s a reason. Calm wording, what happened, the number, and what to do.

Caution
Your heart rate went above your limit, or after the cold it isn’t coming down. A haptic tap and a short message: leave the sauna, sit down.
Stop
Above your limit for minutes, or still high after five minutes of rest. Full screen, repeated every 30 seconds, with the local emergency number.
  • Default limit: 85 % of your estimated maximum heart rate, from your age; you can set your own.
  • Log alcohol or caffeine before starting and the limits are lowered, and the alert tells you why.
  • If you take beta blockers or similar medicines, tell Kiuas: the limit follows a formula made for them.
  • No heart rate signal, no alerts: the Watch says so instead of staying silent.
Apple Watch caution: heart rate 164 above your limit, leave the sauna and sit somewhere cool.
Caution
Apple Watch stop alert: better to stop here for today. While resting, your heart rate has been above 100 for 5 minutes.
Stop

Kiuas is not a medical device

  • Alerts are a help, not a diagnosis. They can be late or wrong.
  • If you have heart or blood pressure problems, are pregnant or take medication, ask your doctor before sauna and cold water.
  • If you feel unwell, get out and ask for help. Your body matters more than the timer.

Privacy

Your sessions stay with you

Accounts

0

Servers

0

Trackers

0

Kiuas has no account, no server of its own and no analytics. Your sessions live on your iPhone, your Apple Watch and in Apple Health, and leave them only when you share an export yourself.

Read the privacy policy