What is cardiac drift?

Cardiac drift refers to the phenomenon where heart rate increases during prolonged exercise, even when the intensity of the activity remains constant. Andrew Huberman explains that this often occurs in hotter environments.

When someone exercises in a controlled temperature, their heart rate stabilizes at a certain level. However, if the temperature rises, their heart rate also increases due to cardiac drift. This increase happens because the body has to work harder to cool itself down, adding to the cardiovascular strain from the exercise itself. The combined effect of heat and exercise can lead to an elevated heart rate that can make the person feel the need to stop sooner than they would in cooler conditions 1.