The Effects of Stretching Training on Arterial Function and Autonomic Control

Hypertension is a major risk factor for cardiovascular disease. Hypertension and abdominal obesity are associated with dysfunction of the main mechanisms of cardiovascular regulation, the autonomic nervous system and the vascular endothelium. Increased sympathetic activity and endothelial dysfunction are associated with increased arterial stiffness, which is an independent risk factor for the development of hypertension and other cardiovascular diseases. The recommended intervention for controlling BP in pre- and stage 1- hypertensive individuals is lifestyle modifications such as exercise, and not drug therapy.Although aerobic and resistance exercise has been shown to be beneficial for the cardiovascular system, special populations such as the elderly and obese may have physical and/or musculoskeletal limitations which may limit their participation in these exercise modalities.

Stretching is a form of exercise that is widely recommended for injury prevention. Among the benefits of stretching are an increased flexibility, enhanced muscular coordination, stress relief, improved range of motion and an improved posture. Previous studies have shown stretching training to increase arterial compliance and acutely increase sympathetic nerve activity. In addition, low flexibility levels have been found to be associated with arterial stiffness. Given that stretching of skeletal muscle causes an increase in sympathetic nerve activity; repetitive stimulation of sympathetic activity induced by habitual stretching, might chronically reduce resting sympathetic activity. The reduction in sympathetic activity might result in a decrease of arterial stiffness and blood pressure.

The investigators hypothesis is that 8 weeks of stretching training would reduce arterial stiffness, blood pressure and sympathetic activity in obese women. The investigators also hypothesize that the improved arterial function with stretching would be associated with increases in flexibility levels.

The purpose of this study is to examine the effects of 8 weeks of stretching training on blood pressure,arterial stiffness, wave reflection, endothelial function and cardiovascular autonomic control. The specific aim of the study is:

- To evaluate the effects of 8 weeks of ST on arterial function and aortic hemodynamics by assessing arterial stiffness (aortic, systemic, and leg), aortic blood pressure and wave reflection, and autonomic function (heart rate variability, vascular sympathetic activity \[low-frequency power of systolic BP variability\], and baroreflex sensitivity)

Eligibility Criteria:
Inclusion Criteria:

* 50-65 years old
* Blood pressure between 121/81 and 159/99 mmHg
* Body mass index of 25-39.9
* Sedentary or low active (less than 2 hr per wk)

Exclusion Criteria:

* Younger than 50 or older than 65 years of age
* Body mass index lower than 25, or 40 or higher
* Physically active or competitively active
* Smoker
* Systolic blood pressure higher than 160 mmHg
* Use of hormone replacement therapy of less than 1 yr
* Use of calcium channel blocker or beta blockers
* Type 1 diabetes
* Type 2 diabetes
* Known cardiovascular disease