The adrenal glands are essential to the maintenance of homeostasis, or balance of the human body at rest and during exercise. By interacting with the heart, blood vessels and capillaries, nervous system, lungs, kidneys, skin and other organs, the hormones secreted by the adrenal glands function to help the body maintain its health whether at rest or engaged in exercise.
Identification
The adrenal gland or suprarenal glands are a pair of small triangular glands located in the abdomen directly above the kidneys. As a part of the endocrine system, the adrenal glands function in tandem with the hypothalamus and pituitary glands. Anatomically the adrenal gland has two parts: the medulla or inner portion and the cortex or outer portion.
Function
The medullary portion of the adrenal gland secretes norepinephrine and epinephrine or catecholamines, which are the neurotransmitters of the sympathetic nervous system. The sympathetic nervous system regulates the body's response to stress or "fight or flight" response. Epinephrine stimulates an increase in heart rate and force of cardiac contractions, increases blood flow to the muscles and brain and facilitates the breakdown of glycogen to glucose in the liver. Norepinephrine is a potent vasoconstrictor that causes an increase in blood pressure. Catecholamines also stimulate perspiration and decrease intestinal blood flow.
The adrenal cortex secretes the corticosteroid hormones, aldosterone, and androgen hormones. The corticosteroid hormones or hydrocortisone and corticosterone, are an important regulator of how the body uses fats, proteins and carbohydrates. Aldosterone is an important regulator of sodium balance, blood volume and pressure. (Ref 1)
Adrenal Gland and Exercise
In order to meet the dynamic metabolic demands of the body during exercise, the adrenal gland functions to orchestrate heart rate, blood pressure, blood volume, respiration, perspiration and distribution of blood flow to the brain, muscles and intestines. Norepinephrine and epinephrine released from the adrenal medulla cause an increase in the rate and force of contraction of the heart and constriction of arteries. The increase in heart rate and force of contraction increases stroke volume, or the amount of blood being pumped per heartbeat. This increased blood flow is then distributed throughout the body as needed during exercise. Blood flow to the brain, heart and muscles increases, while blood flow to the intestines decreases. Blood glucose increases to meet the increased metabolic demands of the musculoskeletal system, brain and heart. The bronchioles of the lungs dilate and respirations increase, thereby increasing oxygen intake needed to meet the increased oxygen demands of exercise. Perspiration prevents the body from overheating. Aldosterone released from the adrenal cortex stimulates the kidney to retain salt and water, which protects the body from dehydration and low blood volume.
Cautions
Diseases such as high blood pressure, heart disease, diabetes and kidney disease are often treated with medications that can affect the functions of the adrenal gland. Antihypertensive and cardiac medications such as beta blockers and calcium channel blockers can slow down your heart rate before, during and after exercise. Diuretics, or "water pills," affect salt and water retention by the kidney. To maximize safety in exercise, discuss all exercise plans with your doctor. Ask questions about how your medications might affect your body's response to exercise. A qualified health care professional will make you aware of any exercise precautions or prohibitions that are relevant to your medical history.
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