You’ve probably been there: cruising at your usual long-run pace, feeling strong and steady, when your watch throws you a curveball—your heart rate’s climbing, but your pace hasn’t budged. That sneaky upward creep is referred to as cardiac drift, and we’re here to help you understand it and keep it from derailing your run.
What is it?
Cardiac drift is a physiological phenomenon where, during a longer workout, your heart rate goes up even if your perceived effort level stays the same. As you run, your body loses fluids through sweat, and your blood volume decreases. To compensate, your heart works harder to pump blood, leading to a higher heart rate. Add in factors like heat, humidity or poor hydration, and cardiac drift can hit even sooner (or harder).
How it impacts you
For most recreational runners, cardiac drift is something you might notice reflected in your long-run-data, and shouldn’t worry about (it’s natural and unavoidable). However, if you’re training for a race or working toward specific paces, that creeping heart rate may be signalling that you’re working too hard, which can lead to premature fatigue, longer recovery times and potentially falling short of your performance goals. Recognizing that cardiac drift is natural allows you to plan ahead and adjust your training to minimize its impact.
Can you prevent it?
While you can’t avoid cardiac drift, there are strategies for minimizing it:
Hydrate smart: Start your run well-hydrated and consider electrolyte drinks on longer runs.
Pace yourself: Keep an eye on effort levels rather than chasing a specific pace, especially on hot days.
Acclimatize to heat: Training in warmer conditions helps your body adapt, reducing the impact of cardiac drift.
Build endurance: Stronger cardiovascular fitness can delay the onset of drift, so stick to consistent aerobic training.
The bottom line
Cardiac drift is a natural part of running physiology. The key is to recognize when it’s happening and adjust accordingly. If you pay attention to the signals your body gives you and train wisely, that rising heart rate won’t sideline interfere with your running goals—it’ll just be another training factor you’ve learned to manage.
