Fitness Exercise Science · Supplementary · from Fitness 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:

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

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

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