A 32-year-old man with no past medical history presented to the emergency department after losing consciousness at the end of a half-marathon. The patient was in his usual state of good health until the last mile of the marathon when he began to feel unsteady on his feet and short of breath. At the end of the race, he collapsed and was found unresponsive by EMS. The patient had no memory of the subsequent events and could only recall waking up in the emergency department feeling “numb” and “confused” several hours later. The patient denied any palpitations, chest pain, nausea, blurry vision, dizziness, urinary incontinence, or headache before or after the event. Of note, he was running outside approximately 3 to 4 times a week prior to this episode.