Abstract
BACKGROUND: An 18-year-old female middle-distance runner was referred for loss of consciousness (LOC) during races. CASE SUMMARY: A treadmill exercise test was completed with direct, continuous measures of arterial blood pressure. We were able to elicit LOC during maximal exertion on 2 occasions. Beat-by-beat arterial pressure demonstrated that the LOC occurred despite having normal exercising blood pressure. DISCUSSION: We demonstrate an instructive case in which LOC during maximal exertion may be a consequence of an athlete exercising outside of their physiological limits in the absence of hypotension, causing cerebral hypoperfusion and subsequent syncope. TAKE-HOME MESSAGE: In highly motivated athletes, LOC may occur during maximal exercise in the absence of hypotension.