Glucose and the human body
Carbohydrate, specifically glucose, is the primary energy source during vigorous exercise. Carbohydrates are the human body’s key source of energy, and glucose is the principal fuel for the brain. Any extreme fl uctuations in blood glucose levels can be extremely dangerous; too little can inhibit performance, whereas too much can damage the vascular system. Control of blood glucose is regulated by the pancreas, which produces two specific hormones: insulin and glucagon.
Relationship between insulin and glucose
Insulin helps regulate energy and glucose metabolism in the body. After consuming a meal, glucose enters the blood at the small intestine, causing a rise in blood glucose levels. As the blood is circulated through the pancreas, elevated levels of glucose trigger the release of insulin. The circulating insulin binds with the receptors of its target cells (in this case skeletal muscle or liver cells), and the cell membrane becomes more permeable to glucose. Glucose then diffuses out of the bloodstream and into the cell. The net result is a drop in blood glucose levels. Thus insulin causes cells in the liver, muscle, and fat tissue to take up glucose from the blood, storing it as glycogen in the liver and muscle (50,51).
Relationship between glucagon and glucose
Glucagon is one of the two hormones secreted by the pancreas that regulate blood glucose levels. Its effect is opposite to that of insulin, as it functions to raise blood glucose levels by triggering the release of glycogen stores from the liver (glycogen is the stored form of glucose). Hours after a meal, or as a result of a combination of normal metabolic processes and physical activity, the body will begin to exhibit lower blood glucose levels. The drop in circulating blood glucose levels triggers the release of glucagon from the pancreas. In contrast to insulin, glucagon has a much more specific effect, stimulating the liver to convert its glycogen stores back into glucose, which is then released into the bloodstream.
Relationship between insulin and glucagon
Understanding the effects of exercise is helpful to understanding the interrelationship between insulin and glucagon. As activity levels increase, glucose uptake by the body’s cells also increases. This is the result of an increased sensitivity of the cells to insulin; thus, insulin levels will drop during physical activity (52). At the same time glucagon secretion by the pancreas increases, thus helping maintain a steady supply of blood glucose.
