Fig. 3.
Ventilatory responses during exercise. Exercise was performed with intact (control) and blocked (fentanyl) leg muscle afferent feedback in nomoxia, normocapnic hypoxia, and normoxic hypercapnia conditions. V̇e, minute ventilation; fB, breathing frequency; VT, tidal volume. *Significantly different from the fentanyl trial, P < 0.05.