Inadequate ventilation is not usually considered an exercise-limiting factor because it is thought that the respiratory system's maximum ventilatory capacity is never reached during exercise. This so-called reserve can be defined as the difference between the ventilated volume, attained during a maximum voluntary ventilation manoeuvre (MVV) and the maximum ventilation ð _VEmax Þ achieved during exercise. This study explores the relationship between ventilatory capacity, the MVV manoeuvre, and respiratory function. Twelve healthy adults completed a maximal cycle test and 12-, 30-, and 60-s MVV manoeuvres while seated or standing. The MVV12 manoeuvre produced the largest ventilation volume (115 ± 22 vs. ð _VEmax Þ 102 ± 23 L min-1), signifying a reserve of 13%. With longer MVV (30 and 60 s) manoeuvres, the ventilated volume and ð _VEmax Þ were the same, signifying no reserve. MVV increased with the forced expiratory volume at one second, FEV1. The breath rates were approximately 120 vs. 48 ± 6 breaths min-1and tidal volumes were approximately 1 vs. 2.2 ± 0.5 L during the MVV and exercise, respectively. The longer MVV manoeuvre provides the best estimate of ventilatory capacity and shows that 100% of the reserve is used during maximal exercise. A nomogram relating MVV to FEV1 is shown.