Hormones

 

Hormones play major roles in the biochemistry of exercise.

• Cortisol, the major glucocorticoid steroid and a stress hormone, is released from the adrenal glands during exercise and affects cell metabolism throughout the body.

• Activation of the hormone norepinephrine early in exercise and increased blood levels of epinephrine later in exercise stimulate the release of glucose from the liver and fatty acids from adipose tissue.

• Glucagon is a hormone that increases blood sugar levels during exercise by stimulating glycogen breakdown in the liver.

• Several metabolic pathways—including glucose uptake, amino acid transport, and protein and glycogen synthesis—become increasingly sensitive to insulin during and after exercise.

• Insulin and the sex hormone testosterone help regulate protein synthesis in muscle and affect muscle hypertrophy. Insulin may slow any increase in the breakdown of muscle protein following exercise, especially in younger people.

• Energy-regulating hormones, such as leptin, affect AMPK activity.

• Interleukin-6 (IL-6) is released by muscle during exercise and appears to stimulate the hydrolysis of stored fuel in muscle, liver, and fat tissues, as well as activating AMPK in these tissues.

• Various hormones that are stimulated by exercise affect digestion and may speed it up.

• Exercise has both acute and delayed effects on melatonin secretion, which is involved in regulating biological or circadian rhythms.

• Exercise significantly increases secretion of growth hormone.

• Endorphins released during exercise provide pain relief and feelings of well-being.