Individual vasodilatory response heterogeneity during progressive forearm exercise: evidence for vasodilator phenotypes

PURPOSE To determine whether vasodilator and/or pressor response phenotypes are present during a perfusion pressure induced perturbation to exercising muscle oxygen delivery (O 2 D). METHODS 10 healthy male subjects (19.5±0.4 yrs) completed two trials of progressive handgrip exercise to exhaustion (2.5kg increments every 3.5 mins) in each forearm above and below heart level (forearm arterial perfusion pressure (FAPP) Δ 29.5±0.97mmHg). Forearm blood flow ((FBF (ml/min); brachial artery Doppler and echo ultrasound), mean arterial blood pressure (MAP (mmHg); finger photoplethysmography) and O 2 D (ml/O 2 /min; venous effluents) were measured at the end of each work rate (WR). RESULTS Group level, Δ FBF was compromised beyond the 5kg WR in above vs. below. There was no vasodilatory (P=0.21) or exercise pressor (P=0.63) response, and submax O 2 D, submax and peak VO 2 and peak WR were compromised by reduced FAPP (all P<0.05). In contrast, individual responses revealed compensatory vasodilators (n=6) and those who did not (n=4). Vasodilators blunted the FAPP‐evoked reduction in submax O 2 D and VO 2 compared to non‐vasodilators (P<0.05), and experienced less of a compromise to peak WR (P<0.05). CONCLUSIONS In the current model, vasodilatory response phenotypes exist, which determine hypoperfusion susceptibility and the degree to which aerobic metabolism and exercise performance are compromised. NSERC.