HISTORY: A 14-year-old male junior high school football player presented to the emergency department with a history of bilateral thigh pain for three days. The pain began four hours after a vigorous unsupervised lower extremity weight training session and progressively worsened. The training session consisted of: leg extension (two sets of 5 repetitions with 100 lbs), leg press (two sets of 5 repetitions with 310 lbs), and squats (three sets of 5 repetitions with 140 lbs). Three days later he had difficulty standing from a sitting position without assistance. He did not report numbness or paresthesias on his legs. There was no history of blunt trauma or crush injuries. There was a history of a pruritic rash on his thighs for the past month. The patient denied taking any medications, illicit drugs or performance enhancing substances. Other than a history of eczema, past medical history was unremarkable. Family history was positive for several autoimmune diseases but was negative for neuromuscular diseases. The patient reported an intense desire to increase his muscle bulk to improve his performance in school football. PHYSICAL EXAMINATION: Exam in the emergency department revealed an alert adolescent male patient in moderate distress from pain. Weight was 86.3 Kg (> 95th%) and height was 174.5 cm (95th-97th%) with a blood pressure of 124/88 mmHg, a pulse of 70 beats/min, a respiratory rate of 16 breaths/min, and a temperature of 98.6°F. General examination and cranial nerve examination were normal. The lower extremities revealed soft compartments with significant muscular tenderness localized to the anterior, medial and lateral aspects of thighs bilaterally; distal perfusion was intact based on both normal pulses and capillary refill time. Neurologic examination was normal with the exception of bilateral symmetric quadriceps muscle strength of 4/5. There was no muscle atrophy. A mild erythematous maculo-papular rash was seen on the anterior aspect of both thighs. Gait was antalgic and waddling. Coordination was normal. Sensation was intact to light touch and pinprick. DIFFERENTIAL DIAGNOSIS: Exertional Rhabdomyolysis Dermatomyositis Muscular Dystrophy TEST AND RESULTS: On the day of admission, urine obtained for analysis was dip positive for the presence of blood and was negative therafter. Laboratory studies revealed normal complete blood count (including platelets), normal serum electrolytes, normal blood urea nitrogen (BUN) and creatinine (Cr), and normal antinuclear antibody (ANA) and dsDNA. Erythrocyte sedimentation rate (ESR) was 18 mm/hr. The levels of creatine kinase (CK) post exercise were: 35,596 U/L at 72 hrs; 41,050 U/L at 6 days; 10,583 U/L at 8 days; and 136 U/L at 18 days. FINAL/WORKING DIAGNOSIS: Exertional Rhabdomyolysis Mild Eczema TREATMENT AND OUTCOMES: IV hyperhydration and alkalinization with sodium bicarbonate Improvement of eczema with 1% hydrocortisone cream Discharged home with follow up labs after 3 days of inpatient treatment Physical therapy referral for a program of gradual reintroduction to strength training after normalization of muscle enzymes Guidance regarding judicious use of weight training was emphasized Discussed supervision of weight training sessions with school coach