28 people in study, the study participants are taking three times the recommended daily Allegra dose, in addition to a less common H2 inhibitor. All this, only 1 hour prior to a workout.
Post-exercise muscle perfusion is dependent on H1/H2 receptor signaling
To study the effects of H1/H2 blockade on the hemodynamic response during and after interval cycling exercise, healthy adults performed a single exercise session with either placebo (control) or H1/H2 antagonist intake (blockade) on separate days in a randomized and single-blinded design. At rest, acute ingestion of H1/H2 blockers did not alter heart rate, brachial blood pressure, femoral arterial blood flow, or femoral arterial diameter (table S1). The heart rate response during exercise was not different between the placebo and blockade trial (fig. S1A). Muscle perfusion was increased approximately threefold 15 min after exercise and was still ~50% above baseline after 2 hours of passive recovery in the placebo condition. However, the total post-exercise muscle perfusion, expressed as iAUC (incremental area under the curve), was significantly reduced with H1/H2 blockade by ~35%. The brachial arterial blood pressure showed a modest increase during the 2-hour post-exercise period (main effect time) and was, in general, higher after placebo intake (main effect condition). The increase in post-exercise vascular conductance, an important measure of vascular tone, was consequently blunted with H1/H2 blockade. Similar to during exercise, post-exercise heart rate recovery was unaffected by H1/H2 blockade (fig. S1C). Collectively, these data demonstrate that histamine H1/H2 receptors are essential for the regulation of sustained elevation of muscle perfusion following interval exercise.