Fig 1. A schematic of the study design showing the procedures for each visit.

Subjects underwent testing to determine peak oxygen uptake (VO_2peak) and a blood draw prior to randomization to placebo or histamine blockade (Visit 1). The order in which the blockade/placebo (visits 2 or 3) were administered was randomized. During study visits 2 and 3, cardiovascular (CV) measurements were obtained at rest and at 30 min, 60 min and 90 min post-exercise (during recovery).