For many true experimental designs, pretest-posttest designs are the preferred method to compare participant groups and measure the degree of change occurring as a result of treatments or interventions.
Itâs important to note that the flush caused by niacin is not harmful or dangerous. It is actually a sign of improved blood flow and circulation. Also niacin oxygenates the blood. When you get a niacin âflushâ it is an indication that the niacin is causing small blood vessels in your body to expand in size.Many of your small blood vessels, called capillaries, are so small that blood cells can only go through them in single file or if they are flexible enough to fold over.t is actually a sign of improved blood flow and circulation. Also niacin oxygenates the blood. When you get a niacin âflushâ it is an indication that the niacin is causing small blood vessels in your body to expand in size.
Blood contains oxygen and nutrients the body needs to survive. The arteries, veins and capillaries are types of blood vessels that transport the vital blood throughout the body. Learn the differences between the types of blood vessels. Capillaries are the smallest blood vessels. 2  They connect to the arteries and the veins. 3  Capillaries are extremely small tubes that average 6 to 8 micron in size; they are too small to see without a microscope.