Examining vascular mechanisms for the blood pressure lowering effect of resistance training
Creators: name: Banks, Nile Ferguson
Publisher: name: University of Iowa
Year: 2023
Subjects: Blood
Pressure
Resistance
Vascular
public abstract
Exercise
Hypertension

description: Roughly 1.4 billion individuals worldwide have hypertension, and it is at least partially responsible for 20% of annual deaths in the United States. Individuals with high blood pressure often have impaired vascular endothelial function, central arterial stiffness, inflammatory profiles, and elevated sympathetic nervous system activity, all of which, alongside of blood pressure, independently predict future cardiovascular disease (CVD). Elevated blood pressure is defined as having a systolic blood pressure (SBP) between 120–129 mmHg and a diastolic blood pressure (DBP) of &lt; 80 mmHg, whereas stage 1 hypertension is defined as a SBP between 130–139 mmHg or a DBP between 80–89 mmHg. It is recommended that individuals with elevated blood pressure or stage 1 hypertension (ES1H) are to be treated with lifestyle modifications prior to antihypertensive medication. Engaging in resistance exercise training (RT) is one of the lifestyle modifications recommended to these individuals to lower their blood pressure, and while RT has consistently been shown to reduce blood pressure, the mechanisms by which it does so are relatively unclear. The most consistent explanation as to why RT lowers blood pressure is through improvements in vascular endothelial function. Although this has been shown in a variety of populations, evidence is limited in middle-aged to older (MA/O) adults with untreated high blood pressure, who represent a large proportion of individuals with hypertension. Additionally, data suggest that RT may be either ineffective or have a potentially harmful effect on central arterial stiffness and autonomic function, which need to be further explored.Brachial artery flow-mediated dilation (FMD) is the gold standard for testing vascular endothelial function non-invasively and improves following multi-week RT interventions. Improvements in FMD are likely the result of repeated increases in blood flow during each RT session which increases nitric oxide (NO) bioavailability, the key regulator of vascular endothelial function. This improvement in vascular endothelial function results in reductions in total peripheral resistance, and therefore blood pressure. Interestingly, in many studies implementing RT interventions, there are paradoxical increases in central arterial stiffness alongside improvements in endothelial function and blood pressure. Therefore, the major aim of Chapter 2 is to investigate the impact of a 9-week RT intervention on blood pressure, vascular function, central arterial stiffness, autonomic function, and inflammation in MA/O adults with untreated high blood pressure. We report significant improvements in SBP, DBP, and FMD, with no changes in central arterial stiffness, autonomic function, or inflammation. These data support the prescription of RT as a lifestyle modification to reduce blood pressure in those with ES1H.
description: RT involves repeated muscle contractions to move external loads, resulting in transient elevations in blood flow, increased sympathetic nervous system (SNS) activity, and microtrauma to skeletal muscle fibers. A single RT session causes decreased vascular endothelial function, increased central arterial stiffness, altered autonomic function, and increased inflammation for at least 24 hours following the completion of the exercise session. However, whether these effects are dependent on training status is unclear. Additionally, there is limited evidence suggesting how long one should wait following a RT session before testing vascular and hemodynamic measurements, which impacts the interpretation of all prior studies which have implemented RT interventions. If increased training status does not reduce the acute decreases in vascular function and central arterial stiffness reported in the days following a RT session, the cardioprotective benefit of RT is likely reduced and interventions aimed at accelerating the recovery process are necessary. Chapter 3 aims to address these issues by reporting on the impact of a single RT session in trained and untrained MA/O adults with untreated high blood pressure. Our findings indicate that FMD is reduced for 20–24 hours following a single RT session in trained individuals, baroreflex sensitivity is reduced for 20–24 hours post-training in untrained individuals, while CRP is increased in both trained and untrained individuals, and central arterial stiffness does not change in either group. Notably, while FMD only decreased at 20–24 hours post-training in trained individuals, it remained higher than that of untrained individuals during the recovery period. The reductions in baroreflex sensitivity in the untrained but not trained group is also noteworthy, and studies investigating the acute impact of RT should strongly consider the impact of training status on their outcomes.