Which metric is essential when prescribing exercise intensity using HRR?

• A. Resting heart rate
• B. Heart rate reserve (HRR)
• C. Max heart rate
• D. Recovery heart rate

Answer: (B)

When prescribing exercise intensity with HRR, the important idea is using the heart rate reserve—the difference between max and resting heart rate—to scale effort. The target heart rate is calculated as resting heart rate plus a fraction of that reserve: HRrest + (HRmax − HRrest) × chosen intensity. This reserve captures how much cardiac work a person can add above their resting level, tailoring the workout to their current fitness and autonomic state.

Resting heart rate alone doesn’t tell you how high you can go, and max heart rate alone ignores the starting baseline. Recovery heart rate is useful for gauging how quickly you bounce back after a session, but it isn’t the method used to set ongoing intensity. Using HRR combines both ends of the spectrum to provide a personalized, scalable intensity.