Fig. 1.

Detailed study timeline. Hyperbaric exposure is shown in atmospheres absolute pressure (ATA) units. A total of seven separate trials were performed. Five trials were performed with tyramine to investigate whether blunting of sympathetic α-adrenergic vasoconstriction (functional sympatholysis) would be less in contracting muscles during hyperoxic exercise than during normoxic exercise. Two trials were performed with phentolamine to examine the effects of α-adrenergic blockade on forearm blood flow and vascular conductance under normoxic and hyperoxic conditions.