Dissertation
Examining vascular mechanisms for the blood pressure lowering effect of resistance training
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Spring 2023
DOI: 10.25820/etd.007272
Abstract
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 < 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.
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.
Details
- Title: Subtitle
- Examining vascular mechanisms for the blood pressure lowering effect of resistance training
- Creators
- Nile Ferguson Banks
- Contributors
- Nathaniel DM Jenkins (Advisor)Darren P Casey (Committee Member)Gary L Pierce (Committee Member)Anna E Stanhewicz (Committee Member)Kara M Whitaker (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Health and Human Physiology
- Date degree season
- Spring 2023
- DOI
- 10.25820/etd.007272
- Publisher
- University of Iowa
- Number of pages
- xiv, 138 pages
- Copyright
- Copyright 2023 Nile Ferguson Banks
- Language
- English
- Date submitted
- 04/24/2023
- Date approved
- 05/02/2023
- Description illustrations
- color illustrations
- Description bibliographic
- Includes bibliographical references (pages 103-138).
- Public Abstract (ETD)
High blood pressure is very common and increases the risk of developing cardiovascular disease (CVD). Resistance training (RT) involves lifting weights to increase muscle mass, gain strength, and improve overall health. RT is recommended as a way to reduce blood pressure without the use of antihypertensive medications. While RT is a recommended treatment option to reduce blood pressure, few studies have investigated how it does so. Additionally, RT has been suggested to worsen other vascular health outcomes that are closely related to blood pressure, creating important questions regarding its overall ability to improve cardiovascular health in people with high blood pressure. Unfortunately, many of the studies that have led to these conclusions are also confounded by experimental design concerns, making it difficult to draw firm conclusions. This dissertation aims to better understand how RT is able to lower blood pressure with a primary focus on underlying vascular mechanisms. A better understanding of how RT is able to lower blood pressure will allow for a better prescription of this type of exercise to improve cardiovascular health. Overall, our findings suggest that when someone with high blood pressure engages in nine weeks of RT, they are able to lower their blood pressure while also improving other indicators of CVD risk. We also show that in the days following a single RT session, individuals who have previously engaged in 9 weeks of RT or who remained inactive both had temporary increases in CVD risk through different mechanisms.
- Academic Unit
- Health, Sport, and Human Physiology
- Record Identifier
- 9984425389602771
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