Inspiratory muscle training improves cerebrovascular and postural control responses during orthostatic stress in older women.

PURPOSE: We aimed to investigate the effect of inspiratory muscle training (IMT) on, hemodynamic, cerebrovascular and postural balance responses during orthostatic stress, in older women. METHODS: Fourteen elderly women were assigned to perform IMT at 50% of maximal inspiratory pressure (MIP) (IMT group, n = 8) or placebo training at 5% MIP (Sham group, n = 6), in a counter-balanced order, using an inspiratory threshold device for 4 weeks. During the protocol, MIP was tested weekly once. In a second visit, blood pressure, heart rate, stroke volume, cardiac output, middle cerebral artery blood flow velocity (MCAv), and ventilation parameters were recorded continuously at rest and during orthostatic stress testing, which was conducted on a force plate to measure center-of-pressure (COP) oscillations (postural balance) and the electromyographic activity of the right medial gastrocnemius and tibialis anterior. RESULTS: IMT increased MIP from second to 4th week. The drops in MCAv, stroke volume, and cardiac output, as well as COP displacements during initial orthostasis decreased post-IMT. CONCLUSION: IMT improves the interplay of the respiratory pump, hemodynamic, cerebrovascular and postural balance responses during orthostatic stress in older women.

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 ±â€¯4 years) performed two orthostatic tests with spontaneous breathing through acute experimental (-9 cm.H2O) or sham load impedance (0 cmH2O) 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.

Sex differences in the contribution of blood pressure to acute changes in aortic augmentation index.

Augmentation index (AIx), derived from aortic pulse waveform, is related to arterial stiffness and increased cardiac workload. Sex differences were observed in the relationship between blood pressure (BP) and AIx at rest. In addition, positive correlation between BP and AIx in men during a pressor stimulus was observed previously. However, whether BP is important to acute changes of AIx also in women is yet to be investigated. Therefore, we sought to investigate whether there are sex differences on the relationship between BP and AIx. In all, 16 men (age 27 ± 5 yr; height 176 ± 1 cm; weight 77 ± 7 kg; mean ± SD) and 13 women (age 26 ± 5 yr; height 164 ± 0.3 cm; weight 63 ± 7 kg; mean ± SD) underwent 3 min of rest followed by 3 min of cold pressor test (CPT). Heart rate during CPT was similar to rest. CPT increased BP in both groups and the magnitude was similar between groups. AIx and left ventricle energy wasted (EW) increased (men Δ13 ± 5% and women Δ17 ± 3%; p > 0.05 for group; men Δ580 ± 242 dynes cm-2 s-1 and women Δ618 ± 123 dynes cm-2 s-1; p > 0.05 for group) similarly in men and women during CPT. A positive Pearson correlation was found between AIx and BP in men (systolic BP (SBP) r = 0.77, p = 0.01; diastolic BP (DBP) r = 0.79, p = 0.01 and mean arterial pressure (MAP) r = 0.83, p < 0.01), however no correlation was seen in women (SBP r = 0.04, p = 0.89; DBP r = 0.24, p = 0.44 and MAP r = 0.23, p = 0.44). The contribution of BP to acute changes in AIx at higher levels of BP is different between men and women.