Which statement best explains why HR-based intensity targets may be less informative for someone with a very low resting heart rate?

• A. Because heart rate is always high during exercise.
• B. Because HR targets are only used for elite athletes.
• C. Because HR-based targets are more reliable in this case.
• D. Because resting heart rate is very low, making HR-based targets less informative.

Answer: (D)

HR-based intensity targets rely on resting heart rate as the baseline for calculating training zones. If the resting rate is very low, the baseline is so far below typical values that day-to-day fluctuations, measurement error, and factors like sleep, caffeine, heat, or dehydration can cause larger swings in the calculated target zones. In highly conditioned individuals, heart rate may rise only modestly with increasing effort, making these HR-based targets less tightly tied to actual intensity. Because of these reasons, resting heart rate being very low can make HR-based intensity targets less informative, so coaches often supplement with other measures like perceived exertion or power/pacing.