Figure 18,1 Maximal and tidal flow-volume loops are shown at rest and during incremental cycle exercise in a healthy, younger (a) and older (b) male subjects. Tidal flow-volume loops are provided at rest (solid line), at a sub maxima I ventilation of approximately 30 L/min (dotted line), and at peak exercise (dashed line). Note expiratory flow limitation (tidal expiratory flow overlapping the maximal curve) and an increase in dynamic end-expiratory lung volume (EELV) during exercise in the older male. (c,d) In the same subjects, lung volumes are shown relative to ventilation during exercise. There are greater volume constraints on VT expansion (solid area) during exercise in the older subject: i.e. increased RV and dynamic EELV, and a relatively reduced inspiratory reserve volume (i.e. IRV = TLC - EILV) at similar submaximal levels of ventilation. See text for definition of abbreviations.