HRV stability

HRV stability shows how much your morning HRV moves from day to day, not how high it is. A steady HRV usually means your body is handling training, sleep and stress well.

Where to find it

Open the Fitness page: tap the Fitness & form card on the Trends tab, or tap the round + button, then Fitness. HRV stability is the second card.

What the number means

It looks at your last 7 healthy mornings and works out how much your HRV moved between them, as a percent. Sick days are left out. It needs at least 5 healthy mornings out of the 7.

• 0% would mean the same HRV every morning. It can't go below 0.
• Lower is steadier. Jumps often follow hard training, short sleep, alcohol, travel or getting sick.

Steady or jumpier

ZONAL compares you only with yourself, over the past year:

• The shaded band on the chart is your usual range. The dashed line is your typical value.
• Jumpier than usual means more up and down than 9 in 10 of your 7-day stretches over the past year.
• Steady means you're inside your usual range.
• Not enough mornings means fewer than 5 healthy mornings in the last 7, for example right after an illness.

One jumpy week isn't a problem. Look for a run of them. And steady doesn't fix a low HRV: it only says your HRV isn't bouncing around.

Sick days on the chart

The line never breaks. Through a sick stretch it keeps going, faded and dashed, under a striped band labeled SICK. Those mornings never count toward your usual range or the label.

Right after an illness the line uses whatever healthy mornings there are so far, so it can spike while it rests on only a few mornings. It settles as more healthy mornings come in.

Ranges

Pick 1M, 3M, 6M, Since (your program start month), 1Y or All. It opens on 3M. Your usual range always comes from the past year, whatever range you pick.

It needs about two months of mornings before it shows. Tap What does this mean? on the card for the short version.

Questions

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