Respiratory pump contributions in cerebrovascular and postural control responses during orthostatic stress in older women.

The acute inspiratory resistive load (IRL) may increase the respiratory pump contributes to hemodynamic responses during orthostatic stress. However, IRL effects on cerebrovascular and postural control interplay is unknown. Fourteen older women (65 ± 4 years) performed two orthostatic tests with spontaneous breathing through acute experimental (-9 cm.HO) or sham load impedance (0 cmHO) connected to a pneumotachograph for breath-by-breath recordings on a facemask. Both tests were executed on a force plate, for postural balance analysis, and electromyographic activity records of calf muscles. Blood pressure, middle cerebral artery blood velocity (MCAv), heart rate (HR), stroke volume (SV), and cardiac output (CO) were continuously recorded. IRL reduced postural instability in the first five seconds at orthostatic position compared to sham. Although the mean blood pressure and MCAv were similar in both conditions, IRL reduced the SV and CO drops, and time to recover MCAv. Therefore, IRL improved postural control, CO and MCAv responses during initial orthostasis.