There are many physical, mental, and physiological
benefits to regular exercise. One category of
benefits is the impact that exercise has on many
of your body’s hormones. Hormones are chemical
messengers within your body that affect almost
all aspects of human function:
1. Growth Hormone
– Stimulates protein synthesis (muscle tone/development),
and strength of bones, tendons, ligaments, and cartilage. –
Decreases use of glucose and increases use of fat as a fuel
during exercise. This helps to reduce body fat and to keep
blood glucose at a normal level which helps you to exercise
for a longer period of time.
Release of growth hormone from the pituitary gland
in the brain is increased with increasing aerobic
exercise time, especially more intense exercise such as
interval training. To receive an article on interval
training, send email to: [email protected]
– An endogenous opioid from the pituitary gland that
blocks pain, decreases appetite, creates a feeling of
euphoria (the exercise high), and reduces tension and
Blood levels of endorphins increase up to five times
resting levels during longer duration (greater than
30 minutes) aerobic exercise at moderate to intense
levels and also during interval training.
Also, after several months of regular exercise, you
develop an increased sensitivity to endorphins (a
higher high from the same level of endorphins), and
endorphins that are produced tend to stay in your
blood for a longer period of time. This makes longer
duration exercise easier (you’re feeling no pain)
and it causes your exercise high to last for a longer
period of time after exercise.
– An important hormone in both males and females for
maintaining muscle tone/volume/strength, increasing
basal metabolic rate (metabolism), decreasing body
fat, and feeling self-confident. It’s produced by the
ovaries in females and by the testes in males.
– Females have only about one tenth the amount of
testosterone that males do, but even at that level in
females it also plays a role in libido and intensity
of orgasms. Production of testosterone in females begins
to decline as a woman begins to approach menopause
and in males it begins to decline in his forties.
Blood levels of testosterone increase with exercise
in both males and females beginning about 20 minutes
into an exercise session, and blood levels may remain
elevated for one to three hours after exercise.
– The most biologically active estrogen, 17 beta
estradiol, increases fat breakdown from body fat stores so
that it can be used and fuel, increases basal metabolic rate
(metabolism), elevates your mood, and increases libido.
This hormone is at much higher blood levels in females,
but the ovaries begin to produce less of it as a woman
begins to approach menopause.
The amount of 17 beta estradiol secreted by the ovaries
increases with exercise, and blood levels may remain
elevated for one to four hours after exercise.
5. Thyroxine (T4)
– A hormone produced by the thyroid gland, Thyroxine
raises the metabolic rate (“metabolism”) of almost
all cells in the body. This increase in “metabolism”
helps you to feel more energetic and also causes you
to expend more calories, and thus is important in
Blood levels of thyroxine increase by about 30%
during exercise and remain elevated for several
hours afterward – this period of time is increased
by an increase in intensity and/or duration of
exercise. Regular exercise also increase thyroxine
levels at rest.
– A hormone produced primarily by the adrenal
medulla that increases the amount of blood the
heart pumps and directs blood flow to where it’s
– Stimulates breakdown of glycogen (stored
carbohydrate) in the active muscles and liver to use
as fuel. It also stimulates the breakdown of fat (in
stored fat and in active muscles) to use as fuel.
The amount of epinephrine released from the adrenal
medulla is proportional to the intensity and
duration of exercise.
An important hormone in regulating (decreasing)
blood levels of glucose (“blood sugar”) and in
directing glucose, fatty acids, and amino
acids into the cells. Insulin secretion by the
pancreas is increased in response to a rise in
blood sugar as is often the case after a meal.
Typically, the larger the meal, or the greater the
quantity of simple sugars consumed, the larger
the insulin response. This is another reason
that it’s good to eat small frequent meals and
to limit consumption of sugar and of processed
bread, pasta and rice. The whole grain (non-
processed) versions of those products are a
much healthier choice.
Blood levels of insulin begin to decrease about 10
minutes into an aerobic exercise session and
continue to decrease through about 70 minutes of
exercise. Regular exercise also increases a cell’s
sensitivity to insulin at rest, so that less is needed.
A hormone that is also secreted by the pancreas,
but it’s job is to raise blood levels of glucose
(“blood sugar”). When blood sugar levels get too
low, glucagon is secreted and causes stored
carbohydrate (glycogen) in the liver to be released
into the blood stream to raise blood sugar to a
normal level. It also causes the breakdown of fat
so that it can be used as fuel.
Glucagon typically begins to be secreted beyond
30 minutes of exercise when blood glucose levels
may begin to decrease.
So, next time you’re exercising, think about all
the wonderful things that are happening to your
hormones. It might even make you want to do more
copyright 2007 by Greg Landry, M.S
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