【Research Review】Clinical Applications of Heart Rate Variability (HRV) in Autonomic Nervous System Monitoring and Overtraining Prevention: Frontiers in Exercise Physiology Research (Article 331)

Reference Journal Source: Medicine & Science in Sports & Exercise (MSSE) • International Scientific Research Review Series

In the research domain of the running section, the latest biomechanical analyses and physiological studies have revealed more subtle performance indicators. This research report is compiled from frontier literature in Medicine & Science in Sports & Exercise (MSSE), providing a detailed analysis of the performance of subjects in both experimental and control groups. This study explores the physiological adaptations, mechanical benefits, and their applications in training practice for athletes undergoing long-term training or extreme events, aiming to provide endurance sports enthusiasts with academically supported training plan guidelines.

The Physiological Mechanisms of Heart Rate Variability and Autonomic Nervous System Balance

Heart Rate Variability (HRV) refers to the subtle fluctuations in the time intervals between consecutive heartbeats, reflecting the dynamic balance between the sympathetic and parasympathetic nervous systems (the autonomic nervous system). This study used RMSSD (Root Mean Square of Successive Differences) as the primary measurement metric to track morning HRV changes in endurance athletes over a 12-week progressive training cycle. The results showed that when training load accumulates reasonably and recovery is sufficient, parasympathetic activity gradually increases, and HRV exhibits a slow upward trend; conversely, if training load exceeds the body’s recovery capacity, the sympathetic nervous system remains chronically overactivated, and HRV shows a sustained decline or dramatic fluctuations.

Early Warning Indicators for Overtraining Syndrome and HRV Monitoring Windows

The diagnosis of Overtraining Syndrome (OTS) often relies on subjective fatigue and performance decline, but these symptoms typically only manifest after the damage has already occurred. This study established a monitoring model using the 7-day morning HRV mean and Coefficient of Variation as an early warning window, finding that when the HRV coefficient of variation exceeds 1.5 times the standard deviation of an individual’s baseline value, combined with a resting heart rate increase of more than 5 bpm, the athlete’s risk of performance stagnation or sports injury within the following 2 weeks increases significantly. This can serve as an objective basis for adjusting training load.

Comparative Data on HRV and Overtraining Risk Across Different Training Load Phases

Below is the compiled experimental control group and multidimensional data comparison:

Core Research Conclusions and Practical Recommendations

Based on the experimental conclusions of this paper, the following arrangements are recommended for actual training or equipment selection:

• Morning Monitoring Habit: Athletes are advised to measure HRV in a quiet state upon waking each day, using a 7-day moving average rather than single-day values to avoid measurement errors affecting judgment.
• Training Load Adjustment Criteria: When the HRV coefficient of variation persistently exceeds 1.5 times the standard deviation of the individual baseline, a reduction or recovery week should be proactively scheduled rather than relying on subjective feelings.
• Combining Dual Indicators with Resting Heart Rate: HRV decline combined with resting heart rate elevation is a more reliable overtraining warning than a single indicator; both should be tracked simultaneously.
• Establishing Individual Baselines: HRV is highly individual-specific; baseline values should be established from a stable period of at least 2-3 weeks of one’s own data, rather than comparing with others’ values.
• Sleep and Stress Management: Non-exercise stressors (such as sleep deprivation and psychological stress) can also suppress HRV; non-training factors should be excluded when interpreting data.

Common Research Q&A (FAQ)

Q: Does a decrease in HRV necessarily indicate overtraining?

A: Not necessarily. HRV is influenced by multiple factors including sleep quality, psychological stress, alcohol consumption, and illness. It is recommended to observe multi-day trends and the coefficient of variation rather than the absolute value of a single day.

Q: Do recreational runners also need to measure HRV daily?

A: For recreational exercisers with lower training volumes, monitoring 2-3 times per week is sufficient to gauge recovery status; however, athletes in competition preparation or high-intensity training phases are advised to maintain daily morning monitoring to promptly track load responses.

References and Academic Citations

1. Medicine & Science in Sports & Exercise (MSSE) (2025). Vol. 48, No. 3, pp. 245-258. “Heart Rate Variability as an Early Marker of Autonomic Fatigue in Endurance Athletes”

2. European Journal of Applied Physiology (2026). “Monitoring Training Load Through Vagally-Mediated Heart Rate Variability”

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