Cardiac drift: gradual HR rise at constant pace during long efforts
LoadGradual rise in heart rate even when pace stays constant, signaling dehydration or accumulated fatigue.
Cardiac drift is the slow HR rise observed on 2+ hour sessions at constant pace. It results from reduced plasma volume (sweating), blood redistribution to the skin (thermoregulation), and increasing glycogenolysis. A drift below 5% is acceptable (e.g., HR goes from 140 to 147 over 3 h). Above 8-10%, session quality drops and overheating risk rises. Drift is a sensitive indicator of hydration and daily form.
In TriPaced:
TriPaced detects cardiac drift on long Strava activities (> 90 min) via the session analysis module. When drift exceeds 8%, the session is flagged as 'high drift' and a hydration reminder appears in the recap.
Source Coyle & Gonzalez-Alonso, 2001: Cardiovascular drift during prolonged exercise, Sports Medicine