# Clinical Cases: Fitness and Exercise Science

## Case 1: Rhabdomyolysis from Extreme Exercise

### Patient Presentation
**Demographics:** 28-year-old male software engineer

**Chief Complaint:** "My muscles are extremely sore and my urine is dark brown."

**History of Present Illness:**
Mr. Kovac presents to the emergency department 36 hours after his first-ever CrossFit workout. Despite having been largely sedentary for the past two years, he attended an introductory class that included 100 pull-ups, 100 push-ups, 100 sit-ups, and a 400-meter run, all performed "for time." He was encouraged by the group atmosphere to push through fatigue and complete the workout, which took him approximately 45 minutes.

Within 12 hours of the workout, he developed severe bilateral upper extremity pain, marked swelling of his biceps and forearms, and inability to fully extend his elbows. The pain was described as 9/10 in intensity and unresponsive to ibuprofen. At 24 hours, he noticed his urine had become dark brown, resembling cola. He became increasingly nauseated and vomited twice before presentation.

He reports drinking only one bottle of water during the workout and approximately three glasses of water in the subsequent 24 hours. He denies supplement or anabolic steroid use. He took no pre-workout stimulants. The ambient temperature during the workout was approximately 85°F in an open-air gym with limited shade.

**Past Medical History:**
- No significant medical history
- No prior hospitalizations or surgeries
- Sickle cell trait (identified on newborn screening; no crises)

**Medications:**
- None
- Denies supplement use, anabolic steroids, or stimulants

**Social History:**
- Software engineer; sedentary occupation
- Social drinker (2-3 beers per weekend)
- Non-smoker
- No recreational drug use
- Previously played college intramural basketball (4+ years ago)

**Family History:**
- Non-contributory

### Physical Examination
- **Vital Signs:** BP 102/68 mmHg, HR 112 bpm, RR 20, Temp 99.8°F, SpO2 98%
- **General:** Muscular male in significant distress due to pain; visibly dehydrated
- **HEENT:** Dry mucous membranes; sunken eyes
- **Cardiovascular:** Tachycardic, regular rhythm; no murmurs; capillary refill 3 seconds
- **Respiratory:** Clear to auscultation; tachypneic
- **Abdomen:** Mild diffuse tenderness; no rebound; hypoactive bowel sounds
- **Extremities:** Bilateral upper extremities markedly swollen and tense; biceps and forearms firm and tender to palpation; elbows held in 90-degree flexion; passive extension elicits severe pain; bilateral grip strength significantly diminished; lower extremities mildly tender in quadriceps; no compartment syndrome signs (intact pulses, sensation, and motor distally)
- **Skin:** Decreased turgor; no rash

### Workup and Results

**Laboratory Studies:**
| Test | Result | Reference Range |
|------|--------|-----------------|
| Creatine Kinase (CK) | 78,400 U/L | 22-198 U/L |
| Myoglobin (serum) | 4,200 ng/mL | < 85 ng/mL |
| Myoglobin (urine) | Positive | Negative |
| BUN | 38 mg/dL | 7-20 mg/dL |
| Creatinine | 2.1 mg/dL | 0.7-1.3 mg/dL |
| Potassium | 5.8 mEq/L | 3.5-5.0 mEq/L |
| Calcium | 7.2 mg/dL | 8.5-10.5 mg/dL |
| Phosphorus | 6.4 mg/dL | 2.5-4.5 mg/dL |
| Uric Acid | 11.2 mg/dL | 3.5-7.2 mg/dL |
| AST | 1,840 U/L | 10-40 U/L |
| ALT | 620 U/L | 7-56 U/L |
| LDH | 2,450 U/L | 140-280 U/L |
| Lactate | 4.8 mmol/L | 0.5-2.0 mmol/L |
| Urinalysis | Large blood (dipstick); 0-2 RBC/hpf | — |
| Bicarbonate | 18 mEq/L | 22-29 mEq/L |

**Imaging/Additional Studies:**
- ECG: Sinus tachycardia; peaked T-waves in V2-V4 consistent with hyperkalemia
- Point-of-care ultrasound: IVC collapse > 50% with respiration (volume depletion); no pericardial effusion
- Renal ultrasound: Normal-sized kidneys without hydronephrosis
- Compartment pressures (bilateral forearms): Right 28 mmHg, Left 24 mmHg (borderline; < 30 threshold)

### Clinical Image

![Medical diagram showing the pathophysiology of exertional rhabdomyolysis from skeletal muscle breakdown to myoglobin release, renal tubular obstruction, and acute kidney injury](case_01_image.jpg)

*Pathophysiology of exertional rhabdomyolysis illustrating skeletal muscle cell membrane disruption, release of intracellular contents (myoglobin, CK, potassium, phosphorus) into the circulation, and the mechanism of myoglobin-induced acute kidney injury through renal tubular obstruction and oxidative damage. Source: Educational illustration.*

### Diagnosis
**Exertional Rhabdomyolysis with Acute Kidney Injury (AKIN Stage 2) and Hyperkalemia (ICD-10: M62.82, N17.9, E87.5)**

**Key Diagnostic Criteria:**
- CK > 5x upper limit of normal (78,400 U/L; > 390x normal)
- Myoglobinuria (positive urine blood on dipstick with absent RBCs on microscopy — classic finding)
- Acute kidney injury: Creatinine 2.1 (baseline estimated 0.9-1.0; > 2x increase = AKIN Stage 2)
- Dangerous hyperkalemia (5.8 mEq/L) with ECG changes
- Clear temporal relationship to unaccustomed eccentric exercise

### Treatment Plan
1. **Aggressive IV Fluid Resuscitation:** Normal saline bolus 1-2 L/hour initially, then titrate to maintain urine output > 200-300 mL/hour; target CK downtrend; continue high-volume fluids until CK < 5,000 U/L
2. **Hyperkalemia Management:** IV calcium gluconate 1 g for cardiac membrane stabilization (peaked T-waves); insulin 10 units regular with D50 25 g IV; sodium bicarbonate 50 mEq IV; kayexalate 30 g PO; continuous cardiac monitoring
3. **Urine Alkalinization:** Sodium bicarbonate infusion to maintain urine pH > 6.5 (reduces myoglobin precipitation in renal tubules); monitor serum calcium closely (alkalinization can worsen hypocalcemia)
4. **Avoid Nephrotoxins:** Hold all NSAIDs (patient was taking ibuprofen — may have worsened renal injury); avoid contrast dye
5. **Monitoring:** CK every 6 hours; BMP every 6-8 hours; strict intake/output; Foley catheter for accurate urine output monitoring; compartment pressure re-checks if swelling worsens
6. **Nephrology Consultation:** For AKI management and potential dialysis if oliguric renal failure develops or hyperkalemia becomes refractory
7. **Disposition:** ICU admission for continuous monitoring given hyperkalemia with ECG changes and AKI
8. **Post-Discharge:** Education on gradual exercise progression; discuss sickle cell trait as risk factor for exertional rhabdomyolysis; avoid extreme exercise in heat

### Key Learning Points
- Exertional rhabdomyolysis classically occurs with unaccustomed eccentric exercise (muscle lengthening under load) in deconditioned individuals; the triad is muscle pain, weakness, and dark urine
- The urinalysis hallmark is a positive dipstick for blood with few or no RBCs on microscopy — the dipstick detects the heme moiety in myoglobin, creating a false-positive for blood
- CK levels > 5,000 U/L (and especially > 15,000 U/L) carry significant risk for acute kidney injury; the risk rises steeply above this threshold
- Sickle cell trait is an underrecognized risk factor for exertional rhabdomyolysis and exercise-related sudden death, particularly with intense exercise in heat or at altitude
- Aggressive isotonic fluid resuscitation is the cornerstone of treatment — early and high-volume fluids can prevent the need for dialysis in the majority of cases; NSAIDs are absolutely contraindicated as they worsen renal perfusion

---

## Case 2: Exercise-Induced Bronchoconstriction

### Patient Presentation
**Demographics:** 16-year-old female high school cross-country runner

**Chief Complaint:** "I can't breathe during my races and my times are getting slower."

**History of Present Illness:**
Sophia is a competitive cross-country runner who has noticed increasing difficulty breathing during the last mile of her 5K races over the past cross-country season (September through November). She describes a sensation of "chest tightness and wheezing" that begins approximately 8-10 minutes into sustained hard running and peaks about 5 minutes after she finishes racing. The symptoms resolve spontaneously within 30-45 minutes of stopping exercise.

She reports that the symptoms are significantly worse on cold, dry days and during early morning practices. She denies symptoms at rest, during warm-up, or during low-intensity training runs. She does not experience nocturnal cough, symptoms with allergen exposure, or any other triggers besides exercise. Her coach has noted audible wheezing at the finish line.

Her race times have declined by approximately 90 seconds over the season, and she has become anxious about competition. She has tried "breathing through her nose" and other self-directed strategies without improvement. She has no prior diagnosis of asthma and takes no medications. She has been otherwise healthy.

**Past Medical History:**
- Allergic rhinitis (seasonal, mild; spring pollen)
- Eczema in childhood (resolved by age 8)
- No prior asthma diagnosis
- No hospitalizations

**Medications:**
- Cetirizine 10 mg daily during spring allergy season
- No inhalers or asthma medications

**Social History:**
- 11th grade high school student
- Competitive cross-country runner (3 years)
- No tobacco, alcohol, or drug use
- No pets at home
- Lives in a northern climate with cold, dry autumn weather

**Family History:**
- Mother: Asthma (mild, well-controlled)
- Father: Healthy
- Brother: Eczema

### Physical Examination
- **Vital Signs:** BP 108/64 mmHg, HR 56 bpm, RR 14, Temp 98.4°F, SpO2 99%, BMI 20.1 kg/m²
- **General:** Fit, athletic female in no distress (examined at rest)
- **HEENT:** Mild inferior turbinate edema bilaterally; pale, boggy nasal mucosa; Dennie-Morgan lines under eyes; no nasal polyps
- **Cardiovascular:** Bradycardia (athletic); regular rhythm; no murmurs
- **Respiratory (at rest):** Clear to auscultation bilaterally; no wheezing; good air movement; normal inspiratory-to-expiratory ratio
- **Chest:** No accessory muscle use; no pectus deformity
- **Skin:** Mild xerosis antecubital fossae bilaterally; no active eczema

### Workup and Results

**Laboratory Studies:**
| Test | Result | Reference Range |
|------|--------|-----------------|
| CBC with Differential | WNL; Eosinophils 6% | Eosinophils 1-4% |
| IgE (total) | 185 IU/mL | < 100 IU/mL |
| Spirometry (baseline) | FEV1 102% predicted | > 80% predicted |
| Spirometry (baseline) | FEV1/FVC 0.86 | > 0.80 |

**Eucapnic Voluntary Hyperventilation (EVH) Challenge:**
| Timepoint | FEV1 (% predicted) | Change from Baseline |
|-----------|--------------------|--------------------|
| Baseline | 102% | — |
| 5 min post-EVH | 88% | -14% |
| 10 min post-EVH | 81% | -21% |
| 15 min post-EVH | 86% | -16% |
| 20 min post-EVH | 94% | -8% |
| Post-bronchodilator | 101% | -1% |

**Imaging/Additional Studies:**
- Chest X-ray: Normal; no hyperinflation or infiltrates
- FeNO (fractional exhaled nitric oxide): 38 ppb (elevated; > 25 ppb suggestive of eosinophilic airway inflammation)
- Exercise field test: Audible wheezing at 10 minutes of continuous running in cold air; SpO2 maintained at 96%

### Clinical Image

![Diagram illustrating the pathophysiology of exercise-induced bronchoconstriction showing airway water loss, osmotic changes, mast cell activation, and smooth muscle contraction during exercise in cold dry air](case_02_image.jpg)

*Pathophysiology of exercise-induced bronchoconstriction (EIB) demonstrating the osmotic theory: increased ventilation during exercise causes airway surface liquid evaporation, raising mucosal osmolarity, which triggers mast cell degranulation and release of bronchoconstricting mediators (histamine, leukotrienes, prostaglandins), leading to bronchial smooth muscle contraction. Source: Educational illustration.*

### Diagnosis
**Exercise-Induced Bronchoconstriction (EIB) with Atopic Diathesis (ICD-10: J45.990)**

**Key Diagnostic Criteria:**
- ≥ 10% fall in FEV1 from baseline following EVH challenge (patient: 21% fall — diagnostic and moderate severity)
- Symptoms isolated to sustained vigorous exercise (> 6-8 minutes)
- Complete reversibility with bronchodilator
- Atopic background (allergic rhinitis, childhood eczema, elevated IgE, eosinophilia, elevated FeNO) suggesting underlying airway inflammation
- Normal baseline spirometry (characteristic of EIB)

### Treatment Plan
1. **Pre-exercise Short-Acting Beta-Agonist (SABA):** Albuterol MDI 2 puffs 15-20 minutes before exercise; demonstrate proper inhaler technique with spacer; effective for 2-4 hours
2. **Daily Controller Therapy:** Given elevated FeNO and atopic markers suggesting underlying eosinophilic inflammation, initiate low-dose inhaled corticosteroid (fluticasone 44 mcg 2 puffs BID) for 4-6 weeks, then reassess
3. **Warm-Up Protocol:** Prescribe structured high-intensity interval warm-up (7-8 brief sprints over 20-30 minutes before competition) to induce refractory period — evidence-based strategy that reduces EIB severity by 40-50%
4. **Environmental Strategies:** Wear a heat-exchange mask or buff during cold-weather training to warm and humidify inspired air; when possible, schedule intense efforts during warmer parts of the day
5. **Consider Leukotriene Receptor Antagonist:** Montelukast 10 mg daily as adjunctive therapy if ICS + SABA insufficient; particularly useful given her leukotriene-mediated pathophysiology
6. **Nasal Treatment:** Treat allergic rhinitis with intranasal corticosteroid (fluticasone nasal spray) — nasal inflammation worsens lower airway responsiveness through the unified airway model
7. **Anti-Doping Compliance:** Educate patient and family that albuterol (inhaled, up to 1600 mcg/24 hours) and ICS are permitted by WADA/USADA without a TUE; document diagnosis in medical record
8. **Follow-up:** Repeat EVH challenge or spirometry with exercise challenge in 6-8 weeks; monitor FeNO as a marker of controller therapy response

### Key Learning Points
- Exercise-induced bronchoconstriction (EIB) affects 10-50% of elite athletes (highest prevalence in winter sport and endurance athletes) and is underdiagnosed because baseline spirometry is typically normal
- The eucapnic voluntary hyperventilation (EVH) test is the gold standard for EIB diagnosis, recommended by the IOC; a ≥ 10% fall in FEV1 is diagnostic — exercise testing in the clinic often lacks sufficient ventilatory demand to provoke EIB
- The osmotic theory of EIB posits that water loss from the airway surface during hyperventilation creates a hyperosmolar environment that triggers mast cell mediator release — this explains why cold, dry air exacerbates symptoms
- The refractory period phenomenon (reduced EIB severity for 1-3 hours after an initial bronchoconstrictive episode) can be therapeutically exploited through structured high-intensity interval warm-ups
- EIB with underlying atopic inflammation (elevated FeNO, eosinophilia) responds better to inhaled corticosteroids than EIB without atopy, making FeNO measurement clinically useful for guiding controller therapy decisions

---

## 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:**
| Test | Result | Reference Range |
|------|--------|-----------------|
| Cortisol (morning) | 8.2 µg/dL | 6-23 µg/dL |
| Cortisol (post-ACTH stimulation) | 14.1 µg/dL | > 18 µg/dL |
| Free Testosterone | 0.8 pg/mL | 0.8-10 pg/mL (female) |
| Testosterone/Cortisol Ratio | Decreased 40% from baseline | — |
| ACTH | 52 pg/mL | 7-63 pg/mL |
| TSH | 2.4 mIU/L | 0.4-4.0 mIU/L |
| Free T3 | 1.8 pg/mL | 2.0-4.4 pg/mL |
| Estradiol | 28 pg/mL | Follicular: 12-233 pg/mL |
| LH | 1.2 mIU/mL | Follicular: 2-15 mIU/mL |
| FSH | 1.8 mIU/mL | Follicular: 3-10 mIU/mL |
| Prolactin | 32 ng/mL | 4-23 ng/mL |
| Ferritin | 18 ng/mL | 12-150 ng/mL |
| Iron | 48 µg/dL | 37-145 µg/dL |
| CK (resting) | 890 U/L | 22-198 U/L |
| IgA | 62 mg/dL | 70-400 mg/dL |
| IgG | 580 mg/dL | 700-1600 mg/dL |
| Lymphocyte Count | 0.9 x10³/µL | 1.0-4.8 x10³/µL |
| Glutamine | 380 µmol/L | 500-900 µmol/L |
| IL-6 | 8.4 pg/mL | < 5.0 pg/mL |

**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

![Diagram showing the overtraining syndrome continuum from functional overreaching to non-functional overreaching to overtraining syndrome, with corresponding physiological markers at each stage](case_03_image.jpg)

*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