[Research Review] Clinical Application of Heart Rate Variability (HRV) in Autonomic Nervous System Monitoring and Overtraining Prevention: A Study of Elite Athletes’ Physiological Characteristics (Article 436)

Source Reference: European Journal of Applied Physiology • International Research Findings Review Series

This article explores the clinical application of Heart Rate Variability (HRV) in autonomic nervous system monitoring and overtraining prevention.

Physiological Significance Reflected by HRV

HRV measures the degree of variation in the time intervals between consecutive heartbeats, regulated by the dynamic balance between sympathetic and parasympathetic activity of the autonomic nervous system. Generally speaking, the higher the parasympathetic activity (indicating the body is in a recovery, relaxed state), the higher the HRV value; long-term accumulation of high-intensity training stress, sleep deprivation, or illness and infection are often accompanied by decreased HRV, reflecting relatively heightened sympathetic activity and a body in a “fight-or-flight” rather than “repair” state.

Two Response Patterns of HRV and Overtraining Syndrome (OTS)

Overtraining is not a single linear response; two patterns are commonly observed:

• Sympathetic overtraining: Elevated resting heart rate, persistently decreased HRV, with athletes subjectively experiencing fatigue, irritability, and poor sleep quality
• Parasympathetic overtraining: Commonly seen in the later stages of chronic fatigue accumulation, where resting heart rate is instead lower and HRV values fluctuate with abnormally low variability (lacking normal day-to-day variation). This pattern is harder to identify by simply looking at “HRV levels” alone and requires observation of multi-day trend lines

21-Day Training Load and HRV Changes Comparison (Illustrative)

Key Research Conclusions and Practical Recommendations

• Establish a personal baseline: Absolute HRV values vary from person to person; the key lies in the trend relative to one’s own 7-14 day average, rather than comparing with others
• Consistency in measurement timing: It is recommended to measure upon waking, in a supine resting state, avoiding confounding factors such as caffeine, food intake, and measurement posture that may introduce data noise
• Trends take priority over single-day readings: A single-day HRV decrease does not necessarily indicate overtraining; a reading significantly below baseline for 3 or more consecutive days is a more reliable warning sign
• Combine with subjective scales: HRV should be interpreted alongside the Rating of Perceived Exertion (RPE) and sleep quality records; relying on a single data source can easily lead to misjudgment

Common Research Q&A (FAQ)

Q: Is it normal for HRV to fluctuate every day?

A: Yes. HRV itself is influenced by multiple factors such as breathing, sleep, stress, and alcohol consumption. Daily fluctuations are a normal physiological phenomenon; the key is to look at the multi-day moving average trend rather than single-day absolute values.

Q: Should training be completely stopped when HRV decreases?

A: Not necessarily. You can first reduce the training intensity for that day or switch to active recovery (low-intensity aerobic exercise), then observe the HRV trend over the next 2-3 days before deciding whether a longer rest period is needed.

References and Academic Citations

1. European Journal of Applied Physiology — Research direction on heart rate variability and training load monitoring.
2. Sports Medicine — Literature on autonomic nervous system response patterns in overtraining syndrome.

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