What does heart rate variability measure, and what can a reduced HRV indicate in training status?

• A. HRV measures average heart rate over 24 hours.
• B. HRV measures beat-to-beat variations in heart rate; reduced HRV can indicate stress or overreaching.
• C. HRV measures blood pressure variability.
• D. HRV measures respiratory rate variability.

Answer: (B)

Heart rate variability measures how much the time between successive heartbeats varies from one beat to the next. This beat-to-beat variation reflects how the autonomic nervous system regulates the heart, with higher variability indicating stronger parasympathetic (rest-and-digest) influence and greater adaptability. A reduced HRV suggests a shift toward sympathetic dominance or diminished parasympathetic activity, often due to stress, fatigue, or inadequate recovery. In training status, a persistently lower HRV can signal that the body is stressed or not fully recovered, which may precede performance declines or overreaching, and it can guide you to adjust training load or emphasize recovery. The other options describe different measures (average heart rate, blood pressure variability, respiratory rate variability) that do not capture the beat-to-beat timing HRV assesses.