Fitness Exercise Science · Supplementary · from Fitness Exercise Science

Case 3: Overtraining Syndrome in Elite Athlete

Patient Presentation

Demographics: 24-year-old female elite triathlete

Chief Complaint: "I'm training harder than ever but my performance keeps declining, and I feel terrible."

History of Present Illness: Ms. Lindqvist is a professional triathlete preparing for an Ironman qualification race. Over the past 10 weeks, she has noticed a paradoxical decline in performance despite increasing her training volume from 20 to 28 hours per week. Her swim pace has slowed by 5 seconds per 100 meters, her cycling power output has dropped by 15%, and her run pace has deteriorated by 30 seconds per kilometer.

She describes persistent fatigue that does not improve with rest days (she has taken only two rest days in the past 8 weeks). She reports disturbed sleep despite being exhausted (falling asleep easily but waking at 3-4 AM unable to return to sleep), mood changes including irritability and emotional lability (crying during training sessions), and loss of motivation for a sport she previously loved. She has lost her menstrual period for the past four months (previously regular).

She reports frequent upper respiratory tract infections (three in the past 10 weeks), persistent elevated resting heart rate (10-12 bpm above her normal baseline), and heavy, leaden legs during what should be easy training sessions. Her coach has noted that her heart rate response during maximal intervals has paradoxically decreased — she can no longer reach her previously established heart rate zones despite maximal perceived effort.

She has increased her training intensity to try to "break through the plateau," which has only worsened her symptoms.

Past Medical History:

• Stress fracture of left metatarsal (age 21)
• Iron deficiency anemia (treated, age 22)
• No other significant history

Medications:

• Oral contraceptive pill (discontinued 6 months ago)
• Iron supplement 65 mg daily
• Multivitamin
• Whey protein isolate supplement

Social History:

• Professional triathlete; training is her primary occupation
• In a relationship; reports strain due to mood changes
• Non-smoker; no alcohol (performance-oriented restriction)
• Highly driven, perfectionist personality
• Training: 28 hours/week (swim 8h, bike 12h, run 8h); 2 rest days in past 8 weeks

Family History:

• Mother: Osteoporosis
• Non-contributory otherwise

Physical Examination

• Vital Signs: Resting HR 62 bpm (baseline 50 bpm per athlete records), BP 98/60 mmHg, RR 14, Temp 97.4°F, BMI 18.8 kg/m²
• General: Lean, muscular female appearing fatigued; flat affect
• HEENT: Mild pharyngeal erythema; no exudate; mildly enlarged anterior cervical lymph nodes
• Cardiovascular: Regular rate, low-normal blood pressure; no murmurs
• Respiratory: Clear
• Musculoskeletal: Diffuse muscle tenderness to palpation (quadriceps, calves, deltoids); no focal injuries; bilateral quadriceps and hamstring atrophy compared to prior season photos
• Neurological: Normal reflexes; subjective slowed reaction time
• Psychiatric: PHQ-9 score: 14 (moderate depression); GAD-7: 8 (mild anxiety); reports anhedonia specific to sport

Workup and Results

Laboratory Studies:

Imaging/Additional Studies:

• DEXA scan: Lumbar T-score -1.8 (osteopenia); Z-score -2.1 (below expected for age)
• Heart rate variability: Markedly reduced (RMSSD 18 ms; athlete baseline 65 ms)
• Maximal exercise test: VO2max decreased from 62 to 54 mL/kg/min (13% decline); peak heart rate 168 bpm (previous max 188 bpm — 20 bpm reduction in maximal HR)
• Performance Power Profile: 15% decline in FTP (cycling); 12% decline in vVO2max (running)
• POMS (Profile of Mood States): Inverted iceberg profile (elevated tension, depression, anger, fatigue, confusion; decreased vigor)

Clinical Image

The overtraining continuum illustrating the progression from functional overreaching (normal training adaptation) through non-functional overreaching to overtraining syndrome (OTS), with key distinguishing features including recovery time, performance trajectory, and neuroendocrine changes at each stage. Source: Educational illustration.

Diagnosis

Overtraining Syndrome (OTS) with Relative Energy Deficiency in Sport (RED-S) (ICD-10: T73.3, N91.1, E61.9)

Key Diagnostic Criteria:

• Unexplained performance decline persisting > 8 weeks despite adequate recovery attempts
• Paradoxical decrease in maximal heart rate (parasympathetic OTS variant)
• Blunted cortisol response to ACTH stimulation (HPA axis downregulation)
• Suppressed reproductive axis (functional hypothalamic amenorrhea: low LH, FSH, estradiol)
• Immunosuppression (low IgA, IgG, lymphopenia, depleted glutamine, recurrent infections)
• Osteopenia with Z-score below -2.0 in a young athlete — completes the RED-S triad
• Inverted POMS profile and mood disturbance
• Diagnosis of exclusion: thyroid, iron status, and organic disease excluded

Treatment Plan

1. Mandatory Relative Rest: Immediate reduction to 50% of training volume for minimum 4 weeks, then gradual return based on HRV recovery and symptom resolution; incorporate at least 2 complete rest days per week; expected recovery timeline: 3-6 months
2. Energy Availability Correction: Sports dietitian referral; increase caloric intake to achieve energy availability > 45 kcal/kg fat-free mass/day (current estimated < 25 kcal/kg FFM/day); increase carbohydrate intake to 6-8 g/kg/day for recovery; protein 1.6-2.0 g/kg/day
3. Iron Repletion: Increase ferritin target to > 50 ng/mL for athletic performance; consider IV iron if oral supplementation inadequate (athlete GI absorption often impaired)
4. Bone Health: Calcium 1500 mg/day + vitamin D 2000 IU/day; restoration of menstrual cycles is the priority for bone protection; consider endocrinology referral for bone-active therapy if amenorrhea persists
5. Immune Recovery: Glutamine supplementation 5 g BID; avoid heavy training during URTI episodes; monitor IgA as a marker of mucosal immunity recovery
6. Psychological Support: Sports psychologist referral for perfectionism and identity-related issues; address the athlete's belief that "more training = better performance"; screen for relative compulsive exercise behavior
7. HRV-Guided Return to Training: Use daily morning HRV monitoring (RMSSD) to guide training load; resume high-intensity training only when resting HR returns to baseline and HRV consistently > 40 ms
8. Follow-up: Recheck hormonal panel, immunoglobulins, HRV, and performance markers at 8-week intervals; menstrual cycle monitoring; repeat DEXA in 12 months

Key Learning Points

• Overtraining syndrome is a diagnosis of exclusion defined by unexplained underperformance lasting > 2 months with associated mood disturbance and neuroendocrine disruption, not recoverable by short-term rest
• The parasympathetic variant of OTS is characterized by paradoxically low maximal heart rate, low resting blood pressure, and fatigue — distinguishable from the sympathetic variant (elevated resting HR, insomnia, irritability) seen earlier in the overtraining continuum
• Relative Energy Deficiency in Sport (RED-S) is the modern replacement for the "female athlete triad" and encompasses a broader spectrum of health and performance consequences of low energy availability affecting bone, menstrual function, immunity, cardiovascular health, and psychological well-being
• Immunoglobulin A (IgA) in saliva is the most validated immune biomarker for monitoring overtraining-related immunosuppression and predicting infection risk in athletes
• Heart rate variability (HRV) is the most practical tool for monitoring autonomic recovery and guiding return-to-training protocols — a failure of HRV to recover within 48-72 hours of a hard session indicates insufficient recovery and predicts overreaching

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