Short‐term modulation of the exercise ventilatory response is not diminished in older men

Abstract

We have previously shown that the exercise ventilatory response (EVR; defined as the slope of the relationship between ventilation and CO2 production) is reversibly augmented within a single exercise trial in the presence of added dead space (DS) in healthy young men. This augmentation arises from a mechanism known as short‐term modulation (STM; FASEB J. 21, 765.18. 2007), independent of changes in chemoreceptor (CR) feedback from rest to exercise. We hypothesized that the capacity for STM to augment the EVR with added DS is diminished in healthy older men due to age‐dependent decreases in pulmonary function and increases in EVR. Eleven men (age 69 ± 3 years) were studied at rest and during cycle exercise (10, 30, 50W; not randomized) in Control conditions (no added DS) and with added DS (200, 400, 600ml; randomized). The EVR increased sufficiently with the increasing DS volume (p<0.01), e.g. at 10W, from 33 ± 6 in Control to 47 ± 10 with 600ml DS, such that CO2 was not retained with added DS vs. Control. Hence, the increase in the EVR was not due to increased CR feedback from rest to exercise. Increasing exercise intensity diminished the EVR (p<0.01), e.g. with 400ml DS, from 40 ± 7 at 10W to 34 ± 5 at 50W; and the size of this effect varied by DS level (p<0.05). A very similar response pattern was observed in younger men. We conclude that the capacity for STM to augment the EVR with added DS is not diminished with age in healthy men.Support: The Cain Foundation, The King Foundation, and Presbyterian Hospital of Dallas