Physiological Response to a Training and Detraining Period in Vascular Parameters of Cardiometabolic Risk Factors Subjects: Optimizing Post-exercise Strategies to Maintain Health Benefits in Chilean Adults

Endothelial dysfunction (EDys) is characterized as a phenotypic alteration in the endothelium of the arteries, characterized by prothrombotic, pro-inflammatory, an imbalance between the actions of vasodilators and vasoconstrictors, and small resistance vessels. Functionally, the endothelium acquires a proinflammatory state, with prothrombic properties, and is commonly associated with cardiovascular diseases, such as arterial hypertension (HTN, i.e., higher SBP, DBP], coronary artery disease, chronic heart failure, peripheral artery disease, atherosclerosis, type 2 diabetes mellitus (T2DM), and chronic renal failure. Clinically, a decrease of 0.62% in the endothelial function, measured by flow-mediated dilation (FMD%), is associated with an increase of +20 mmHg in systolic blood pressure (SBP). Functionally, EDys is expressed by FMD%, pulse wave velocity (PWV), or the aortic augmentation index (AIx) of the brachial artery, and Structurally EDys is expressed by the carotid-intima media thickness (c-IMT) among others. Methodologically, both FMD% and c-IMT outcomes can be assessed by a) a non-invasive ultrasound, and b) by other more invasive technics.

Part of the mechanism that explains the reduced vasodilator capacity in EDys includes decreased nitric oxide (NO) production, increased oxidative stress (ROS), and a decrease in the production of hyperpolarizing factors. At the molecular level, the up-regulation of adhesion molecules, generation of macrophage chemoattractant peptide-1, and the production of plasminogen activator inhibitor-1 participate also in the inflammatory response related to the prothrombic state in EDys. Other molecular linked mechanisms include that angiotensin II and endothelin-1, hypercholesterolemia, altered insulin signaling, and hyperglycemia can contribute to EDys. Thus, EDys is a preliminary event before atherosclerosis, increasing plaque accumulation, involving molecular pathophysiological events, but also 'functional' and 'structural' detectable damage, that are highly linked with cardiovascular disease (CVD).

In this sense, the 'elevated' BP, clinically known as prehypertension (preHTN), and the HTN itself, represent an enormous public health issue, considering their high correlation with stroke, coronary heart disease, heart failure, and above to Chile, where there is accelerated aging of the population, where HTN is more common in older adults. The adult population with HTN have several other co-morbidities such as overweight/obesity (~40%), T2DM, and dyslipidemia (i.e. increased low-density lipids [LDL-c], decreased high-density lipids [HDL-c], or increased triglycerides), but are transversely physically inactive ~40% (i.e., to do not adhere to national and international physical activity/exercise training recommendations of at least 150 min/of physical activity/exercise training per week by the WHO guidelines).

Exercise training (ExT), a particular monitored modality of physical activity, can work by previous knowledge, as a 'therapy' for decreasing BP in HTN patients and in those with EDys. ExT is a planned, regulated, and guided physical activity modality, where participants can obtain benefits according to a dose applied (i.e., intensity, volume, frequency per week, density) and the profile (i.e., healthy, or seek with cardiometabolic diseases as HTN, dyslipidemia, T2DM, or others, increase fitness performance, but at the same time improve vascular and health markers such as FMD%, c-IMT, SBP/DBP, or MAP in HTN. ExT can include endurance training (ET), consisting of continuum exercise usually practice at low to 'moderate' intensity (walking/run/cycling/rowing, etc.), resistance training (RT), involving loads and external weights (dumbells, exercise machines with loads) with high impact on muscle and bone mass, but also with cardiovascular benefits as decreasing BP, and the last studied high-intensity interval training (HIIT) modality, which is a low-volume of briefs high-intensity intervals (usually cycling, rowing, or running) interspersed with recovery rest periods, and that show a time-efficient cardiometabolic health. All these three ExT modes have been shown to improve functionally, and structurally the EDys, to reduce BP, and improve several anthropometric, body composition, cardiovascular, metabolic, and physical fitness parameters in HTN patients, being this recently corroborated by the American Colleague of Sports Medicine.

Exercise training in Endothelial dysfunction: A relevant meta-analysis from Higashi et al. revealed that moderate-intensity of ET, increases the nitric oxide availability, promoting improvements in EDys markers in healthy subjects. A Long-term ET promote also regular endothelium-dependent vasodilation, and these physiological stimuli have been associated with lower blood pressure levels in HTN individuals. A very recently published article from Pedralli et al., where after 8-weeks of three different Ext modalities as ET, RT, and CT the authors showed a significant improvement in both BP and EDys markers in HTN patients. However, the relevance of these findings contain several scientific and methodological concerns to be considered and generalized such as a) there were no included the time-efficient exercise modality of HIIT, b) the investigators only reported FMD%, but not other of relevance to the endothelial function as c-IMT, c) there were no different frequencies groups of ExT/week, d) RT group worked at intensities ≥60% until 80% of the maximum strength in patients, the baseline PA level was reported by questionnaires rather than objectively measure PA using accelerometers devices, e) there was no diet control hour before the BP and EDys measurements, and more importantly, there was no control group and included both PreHTN, and HTN participants, among others (reported only results in 'mean', but not inter-individual response to know responders (Rs) and non-responders (NRs) to ExT modes. Additionally, and as a major concern, although there are some evidence that show significant improvements of vascular parameters from exercise training such as FMD% and c-IMT during the exercise-intervention periods, there is no evidence about how to maintain these physiological vascular benefits during 'detraining', where there is scarcity of studies with evidence about potential loss of these vascular adaptations, nor proposals of other minimum exercise-dose to maintain these vascular adaptations during the post-exercise cessation period.