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Cardiovascular diseases (CVD) remain the leading cause of death in developed societies, and "midlife" (50-64 yr) and older (65+) men and women bear the great majority of the burden of CVD. Much of the increased risk of CVD in this population is attributable to CV dysfunction, including adverse changes in the structure and function of the heart, increased systolic blood pressure, and arterial dysfunction. The latter is characterized by increased arterial stiffness and vascular endothelial dysfunction. Conventional aerobic exercise training, as generally recommended in public health guidelines, is an effective strategy to preserve or improve CV function with aging. However, <40% of midlife and older adults meet aerobic exercise guidelines, due in part to time availability-related barriers. As such, there is a need to develop evidence-based time-efficient exercise interventions that promote adherence and optimize CV function in these groups. Two promising interventions that may meet these criteria are interval training and inspiratory muscle strength training (IMST). Limited research suggests these modes of training may improve CV function with time commitments of ≤60 min/wk. This review will summarize the current evidence for interval training and IMST to improve CV function in midlife/older adults and identify key research gaps and future directions.

The genioglossus (GG) muscle is considered the principal protruder muscle of the tongue that dilates and stiffens the pharyngeal airway. We recorded whole muscle and single motor unit (MU) activities in healthy adults performing progressive intensity exercise on a cycle ergometer. Tungsten microelectrodes were inserted percutaneously into the GG of 11 subjects (20-40 years) to record electromyographic (EMG) activities and pulmonary ventilation (VI) at rest and at workload increments up to 300 W. Increases in respiratory drive were associated with increases in VI, mean inspiratory flow (Vt/Ti) and tonic and phasic components of the GG EMG activity. In contrast, individual MUs typically showed expiration-related decreases in firing as exercise intensity increased. We suggest the decrease in MU activity may occur secondary to afferent feedback from lungs/chest wall and that compensation for more negative inspiratory airway pressures generated during heavy exercise occurs primarily via recruitment of previously silent MUs.

Inspiratory resistance training (IRT) yields significant reductions in resting blood pressure and improves vascular endothelial function. Our objective was to quantify the acute effects of IRT on brachial artery flow‐mediated dilation (FMD) and shear rates (SRs) in healthy men and women. Twenty young adults (22.9 ± 3.4 years; 10 male, 10 female) completed a single bout of IRT or Rest condition in a randomized crossover design. Brachial artery FMD was performed before, 10 min after, and 40 min after the assigned condition. Brachial artery blood flow velocities were collected during IRT, separated by breathing cycle phase, and converted into SRs. FMD improved 10 min post‐IRT (+1.86 ± 0.61%; p = 0.025) but returned to baseline by 40 min post‐IRT (p = 0.002). Anterograde SR decreased by 10% and retrograde SR increased 102% during resisted inspiration, relative to baseline SR (p < 0.001). Anterograde SR increased by 7% in men and women (p < 0.001) and retrograde SR decreased by 12% in women but not men (p = 0.022) during unresisted expiration, relative to baseline SR. A single bout of IRT elicits a transient enhancement in FMD in both men and women. Acute IRT‐related enhancements in SRs may contribute to sustained improvements in FMD that have been reported previously. [ABSTRACT FROM AUTHOR]

High intensity, low volume inspiratory muscle strength training (IMST) has favorable effects on casual systolic blood pressure and systemic vascular resistance. However, the acute effects of IMST on heart rate (HR), blood pressure (BP), and sympathetic regulation of vascular resistance and the trajectory of post exercise recovery are not known. We recruited 14 young adults (7 women/7 men, age: 22 ± 2 years) to perform a single bout of high intensity IMST (inspiratory resistance set at 75% of maximal inspiratory pressure) importantly, female and male subjects were matched in regard to the target inspiratory pressure and target inspiratory muscle work per breath. We recorded HR, beat-to-beat changes in BP and postganglionic, muscle sympathetic nerve activities (MSNA) continuously throughout baseline, a single bout of IMST (comprising five sets of 6 inspiratory efforts) and in recovery. We show that one bout of IMST does not effect a change in BP, however, it effects a significant increase in HR (68.4 ± 11.7 beats/min versus 85.4 ± 13.6 beats/min; P < 0.001) and a significant decline in MSNA (6.8 ± 1.1 bursts/15 s bin; P < 0.001 versus 3.6 ± 0.6 bursts/15 s bin) relative to baseline. Remarkably, among men MSNA rebounded to baseline levels within the first minute of recovery, however, in women, MSNA suppression persisted for 5 min. We show that in healthy young adults, high intensity, low volume respiratory training results in the acute suppression of MSNA. Importantly, MSNA suppression is of greater magnitude and longer duration in women than in men. NEW & NOTEWORTHY Previous studies show 6 weeks of high intensity, low volume inspiratory muscle strength training (IMST) lowers blood pressure (BP) and systemic vascular resistance in young adults. However, the acute response to IMST is unknown. We characterized BP, heart rate, and sympathetic nervous activity (SNA) in healthy young adults at baseline, during IMST, and in recovery. There was no acute effect of IMST on BP, however, there was significant IMST-related suppression of SNA that was of greater magnitude in women than men. [ABSTRACT FROM AUTHOR]