Karvonen method — based on heart rate reserve
Heart rate zones allow rowers to train with intention rather than just effort. Each zone targets a different physiological system: UT2 builds the aerobic base and fat-burning efficiency needed for long on-water sessions; UT1 develops cardiovascular capacity at a comfortably sustained pace; AT trains the body to sustain harder efforts before lactate accumulates; TR pushes VO₂max and oxygen transport, building the engine for race-pace work; and AN develops the short, explosive anaerobic capacity used in starts and sprint finishes. Because rowing is an aerobic-dominant sport — even a 2km race is roughly 70–80% aerobic — the majority of training volume should sit in UT2 and UT1, with higher zones used sparingly. Tracking zones via the Karvonen method accounts for individual fitness by using heart rate reserve (the range between resting and maximum heart rate), making the zones more accurate than simple percentages of maximum heart rate alone.