Hormonal responses during exercise

Hormones play important roles in providing energy to the muscles and nerves. They are also involved in replacing that energy. In addition, they play roles in repairing and building tissues. The following are some of the most important functions that hormones perform for athletes.

Endurance work increases the use of glucose by muscles. The following hormones facilitate the use and replacement of muscle glucose. An increase in secretion of the hormone glucagon facilitates the movement of glucose from the liver to the blood, which carries it to the working muscles. The hormones epinephrine (adrenaline) and norepinephrine are also secreted in additional amounts. They aid in the movement of liver glucose to the blood. The secretion of cortisol facilitates the conversion of liver glycogen to glucose. The increased secretion of the hormone insulin, is directly involved in transferring blood glucose into the working muscle fibers.

The hormones cortisol, epinephrine, norepinephrine, and growth hormone also facilitate the conversion of triglycerides that are stored in the liver to free fatty acids and glycerol that the blood can carry to the muscles. There the free fatty acids can be used for energy.

The hormones secreted by the adrenal gland have received the most attention from athletes and coaches. Epinephrine and norepinephrine (also known as the catecholamines) are responsible for the fight or flight mechanism. They stimulate the circulatory system so that it responds to the need for oxygen and glucose more quickly after exercise begins. In fact, an increased secretion of these hormones can take place before exercise begins (also known as the anticipatory response). Anticipatory responses are important because they shorten the response time for various physiological adjustments that facilitate the delivery of energy and the removal of fatigue producing products during exercise.

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