How Tachie works

01

A band, on the arm or chest

Any band that shares heart rate over standard Bluetooth: Polar (H10, H9, Verity Sense, OH1), Garmin watches with Broadcast Heart Rate on, Garmin and Wahoo straps, Coros. Not Apple Watch yet.

Time with the band off during your day counts as your usual for those hours, until you say it was less or more.

02

Five days to learn you

Your first five days of wear measure your resting heart rate and your full day: what a typical day of yours takes. A day counts after 4 hours of wear (2 if you’re mostly in bed), unless you were in a crash.

Then they hold still. If the numbers feel off, Measure again from my data in Settings › Zones works them out from your last two weeks, at once, with an Undo. After a new dose, a new band or a long relapse, Calibrate again there.

03

Rest, Active, High

Your zones start from your resting heart rate. High starts 15 beats above it for most people, the ceiling many people with ME/CFS pace by (Workwell Foundation), and lower if you’re mostly in bed.

Most days	Active from	High from
I can work or study, with limits	resting + 10	resting + 15
I’m mostly at home	resting + 8	resting + 15
I’m mostly in bed	resting + 5	resting + 10
In bed almost all the time	resting + 3	resting + 8

On a beta blocker or ivabradine the gaps are smaller. You can move where Active and High start in Settings › Zones.

04

What a minute costs

Each minute is scored from its average heart rate. Rest costs nothing. Active costs a little, more as you near High. High costs much more, and more the longer it lasts.

Logging adds what heart rate misses, like thinking or talking. Light, moderate or hard counts at least that much, never twice. Add your own activities in Settings › Activities.

If Tachie ever changes what a minute costs, your full day changes with it, so “% left” means the same as before.

05

A full day, and today’s size

Today’s size is a share of your full day, and Today says why in one sentence: “Today is a bit smaller: a big day yesterday.”

Smaller after	By
Big days lately (a crash can come 1–3 days later)	up to 30%
A crash that just ended	20%, then 10%
A higher resting heart rate overnight	10–20%
Poor sleep, or feeling worse	10%, 15%

At most 40% off, and half a day in a crash. The full day itself moves slowly and in the open: smaller after a crash, with an Undo, and offered back after four weeks without one. It only grows when you tap. If you’d rather it never changed on its own, set it to stay as it is in Settings › Daily energy.

06

A buzz when it stays high

Heart rate in High for a minute (two if your heart races when you stand) sends a quiet alert. It says what’s happening, not what to do. At most one every 15 minutes, and “Can’t stop now” quiets them for 15.

Quiet hours, 10 pm to 8 am unless you change them, hold back every alert.

07

“Did you do something?”

When your heart rate rises well above your own usual for five minutes or more, Today asks what it was, so logging is one tap. It compares you with yourself, so standing up with POTS isn’t asked about every time.

Two things in one stretch, like a shower and then getting dressed? Split it and tag each part.

08

Patterns, not verdicts

Your last two weeks, what costs you most, how the days before a crash compared, and a month of resting heart rate. They describe what happened. There’s no score.

Each day keeps the numbers it had at the time, with the zones it had. A small triangle under a day marks where your zones or full day changed, so a jump has a reason you can see.

09

Heart rate only, if you prefer

Rather not think in energy? Today can show just your heart rate against your zones. Tap the big number on Today and pick at the top, or use Settings › Today.