Hormones basically act on the body in three ways by:
- altering the rate of protein synthesis;
- changing the rate of enzyme activity; and
- changing the rate of nutrient transport.
The most popularly-discussed hormones include human growth hormone (hGH), testosterone, epinephrine, norepinephrine, cortisol, insulin, and glutagon because each uniquely affects the cells of the body. Human growth hormone increases protein synthesis, carbohydrate uptake into muscle tissue, muscle growth, and fat mobilization--all favorable effects, especially for bodybuilders. Testosterone is a hormone found primarily in males (females have only about 10% of the amount in males). This hormone is considered anabolic in nature and is responsible for increased lean body mass and strength. Epinephrine and norepinephrine increase glycogen mobilization, heart rate, blood flow to muscles, metabolism, and blood pressure. Cortisol is a catabolic hormone and breaks down muscle tissue, reduces inflammation, and decreases glucose uptake into cells (not favorable for bodybuilders). Insulin, on the other hand, is an anabolic hormone and stimulates the growth of muscle tissue and increases glucose uptake into cells (favorable for bodybuilders). Think of cortisol and insulin as opposite sides of a coin in terms of regulating blood sugar within the body.
Increased blood sugar and/or prolonged exercise triggers the release of insulin from the pancreas in order to enhance the uptake of glucose and amino acids into cells and glycogen into muscles and the liver. Diabetics have problems regulating their blood sugar levels because the pancreas fails to function effectively in terms of releasing adequate insulin for glucose cellular uptake. As a result, blood sugar levels can rise quickly (hyperglycemia) if insulin is not available to provide the transport mechanism of glucose into the cells. Glucagon, also released from the pancreas, serves to balance the amount of insulin released in order to moderate glucose uptake. Notwithstanding diabetes, the human body is capable of regulating hormone levels based on the demands that it is put under (i.e., exercise intensity level).
Brian Danley, CFT
"Motivation is what gets you started. Habit is what keeps you going."