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.
Capillaries are tiny blood vessels connecting the small arteries (arterioles) to the small veins (venules). The blood vessels carry oxygen and nutrients to all the individual cells in the body.rteries carry blood to the tissues, and veins carry blood back to the heart. In betweenare tiny blood vessels so small that red blood cells can pass through single file, allo â¦ wingthe oxygen to diffuse into the surrounding tissue. These are called capillaries.