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.
Rating Newest Oldest. Best Answer: The three main types of blood vessels in the body are arteries, veins, and capillaries. Arteries The arteries are elastic, muscular tubes that carry blood away from the heart, into the capillaries.The walls of the arteries are thicker than the other blood vessels due to higher blood pressure being present in arteries.Note that arteries don't always carry oxygenated blood, as is the case with the pulmonary artery. Veins The veins carry blood from capillaries back to the heart.he walls of the arteries are thicker than the other blood vessels due to higher blood pressure being present in arteries. Note that arteries don't always carry oxygenated blood, as is the case with the pulmonary artery. Veins The veins carry blood from capillaries back to the heart.