Cardiac drift
Cardiac drift is the gradual rise in your heart rate while your pace or power stays the same, during a longer effort. You’re not going harder, and yet your heart beats faster as the session goes on.
What is cardiac drift?
During a long endurance effort a lot changes in your body: you warm up, you lose fluid through sweat, your blood volume drops slightly and your body has to work harder to cool. To keep producing the same output, your heart therefore beats faster. That slow upward drift is normal — a bit of it is to be expected, certainly on hot days or long sessions.
It gets interesting when the drift is bigger than usual for you. If your heart rate climbs more than you’re used to at that pace, that can point to dehydration, heat, or simply an intensity that sits too high for your current endurance base.
What can you do with cardiac drift?
Drift is mainly a reading signal, not a goal in itself. A big, early drift on an easy endurance run is a hint to drink, lower the intensity or accept that the day is hard. A small, late drift on a long session is usually nothing to worry about.
Always read drift against your own habit. How much drift is "normal" differs strongly from person to person — heat sensitivity and disposition play a part — so compare against your own earlier, comparable sessions, not a fixed percentage.
How Trimetra personalises this
Trimetra judges your heart-rate drift against your own baseline: the app learns how much drift is usual for you and notes when a session clearly exceeds it. That signal weighs into your heat and recovery picture, always together with context like temperature and duration — never as a standalone verdict.
Frequently asked questions
Is cardiac drift a problem?
A little drift is normal and comes with long sessions, especially on warm days. It only gets interesting when the drift is clearly larger than usual for you: that can point to dehydration, heat, or an intensity too high for your current endurance base.
How do you reduce cardiac drift?
Short term: drink and lower the intensity. Long term: build your endurance base and acclimatise to the heat — both make your heart rate stay more stable at the same effort.
Why does your heart rate rise at the same pace during a long run?
You warm up, lose fluid through sweat and your body has to work ever harder to cool. To keep delivering the same output, your heart beats faster — that is the drift. Compare it with your own earlier, comparable sessions, not with a fixed percentage.
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