Manipulation of mechanical ventilatory constraint during moderate intensity exercise does not influence dyspnoea in healthy older men and women

We aimed to determine the effect of manipulating mechanical ventilatory constraint during submaximal exercise on dyspnoea in older men and women. Eighteen healthy subjects (aged 60-80years; nine men and nine women) completed two days of testing. On day1, subjects were assessed for pulmonary function and performed a maximal incremental cycle exercise test. On day2, subjects performed three 6-min bouts of cycling at ventilatory threshold, in a single-blind randomized manner, while breathing: (i) normoxic helium-oxygen (HEL) to reduce the work of breathing (W-b) and alleviate expiratory flow limitation (EFL); (ii) through an inspiratory resistance (RES) of similar to 5 cmH(2)OL(-1)s(-1) to increase W-b; and (iii) ambient air as a control (CON). Oesophageal pressure, diaphragm electromyography, and sensory responses (category-ratio 10 Borg scale) were monitored throughout exercise. During the HEL condition, there was a significant decrease in W-b (men: -216%, women: -1710%) relative to CON (both P<0.01). Moreover, if EFL was present during CON (four men and five women), it was alleviated during HEL. Conversely, during the RES condition, W-b (men: 4219%, women: 5016%) significantly increased relative to CON (both P<0.01). There was no main effect of sex on W-b (P=0.59). Across conditions, women reported significantly higher dyspnoea intensity than men (2.90.9vs. 1.9 +/- 0.8 Borg scale units, P<0.05). Despite significant differences in the degree of mechanical ventilatory constraint between conditions, the intensity of dyspnoea was unaffected, independent of sex (P=0.46). When older men and women perform moderate intensity exercise, mechanical ventilatory constraint does not contribute significantly to the sensation of dyspnoea.