Chronic Overtraining Syndrome (OTS): When Passion Becomes Injury

Introduction

Overtraining Syndrome (OTS) is the most serious non-traumatic problem for endurance athletes. Once OTS sets in, recovery can take 6 months to 2 years, and many elite athletes’ careers end because of it. This article provides a comprehensive analysis of this athlete killer, from physiological mechanisms to practical prevention.

Core Definition of OTS

According to the 2013 ECSS/ACSM position statement by Meeusen et al.:

“OTS is a multisystem disorder caused by prolonged high training load and insufficient recovery, characterized by persistent performance decline lasting more than 2 months, with other medical causes excluded.”

Dysregulation of Five Major Systems

Central Fatigue Hypothesis

Newsholme proposed in the 1980s that the core of OTS may be chronic overactivation of the central nervous system 5-HT system:

• High-intensity exercise → increased plasma tryptophan / BCAA ratio
• Tryptophan enters the brain → increased 5-HT synthesis
• Chronically elevated 5-HT → fatigue, depression, decreased performance

This also explains why OTS patients often present with depression-like symptoms.

Differences from Ordinary Fatigue

Risk Factors

• Annual training volume increase > 30%
• TSB < −20 for 2 consecutive months
• Concurrent psychological stress from work, family, exams, etc.
• Chronic sleep < 7 hours
• Repeated illness while continuing to train

Research Directions

Newsholme’s central fatigue hypothesis; Lehmann and Foster’s longitudinal OTS studies on the German national team; Cadegiani and Kater’s EROS study (University of São Paulo, Brazil) updated modern diagnostic criteria; the ECSS/ACSM position statement led by Meeusen is currently the most authoritative clinical guideline.

Practical Recommendations

• Keep annual training volume increase within 10–15%
• Schedule 1 deload week every 3–4 weeks (reduce load by 30–50%)
• Monitor HRV (e.g., HRV4Training, Whoop, Garmin)
• HRV significantly decreased for 3 consecutive days → mandatory rest
• Ensure adequate caloric intake; do not keep carbohydrate ratio too low
• 7.5–9 hours of sleep is one of the core training conditions
• Actively reduce training volume during periods of high psychological stress, rather than training harder as an outlet

Conclusion

OTS is not exclusive to athletes with high training volumes. Amateur cyclists facing a combination of work stress + insufficient sleep + excessive training enthusiasm are actually more likely to fall into the trap. The typical scenario of “training to exhaustion during the New Year holiday + pushing through at work afterward” is common among Taiwanese cyclists. Prevention is always easier than treatment. Combining HRV + subjective fatigue + performance tracking is the most cost-effective health investment for amateur cyclists.

Related Reading

• Identifying, Preventing, and Fully Recovering from Overtraining Syndrome (OTS)
• Complete Recovery Timeline After Overtraining: A Systematic Review of Longitudinal Studies
• Identifying Overtraining Syndrome (OTS) and Returning to a Training Plan
• Recognizing Overtraining Syndrome: 6 Body Warning Signs You Should Not Ignore