Home > Steroid Mechanism
Fahey, T.D. (1998). Anabolic-androgenic steroids:
mechanism of action and effects on performance. In: Encyclopedia of Sports
Medicine and Science, T.D.Fahey (Editor). Internet Society for Sport Science:
http://sportsci.org. 7 March 1998.
How Anabolic
Steroids Work
Steroid
Receptors
Anti-Catabolic
Effects Of Anabolic Steroids
Psychological
Effects
Anabolic Steroids
and Performance
References
Anabolic steroids are drugs that resemble androgenic hormones (sometimes
called male hormones) such as testosterone (Figure 1). Athletes consume them in
the hope of gaining weight, strength, power, speed, endurance, and
aggressiveness. They are widely used by athletes involved in such sports as
track and field (mostly the throwing events), weight lifting, and American
football. However, in spite of their tremendous popularity, their effectiveness
is controversial. The research literature is divided on whether anabolic
steroids enhance physical performance. Yet, almost all athletes who consume
these substances acclaim their beneficial effects. Many athletes feel that they
would not have been as successful without them.
There are several possible reasons for the large differences between
experimental findings and empirical observations. An incredible mystique has
arisen around these substances, providing fertile ground for the placebo effect.
The use of anabolic steroids in the "real world" is considerably different from
that in rigidly controlled, double-blind experiments (in a double blind study,
neither the subject nor experimenter knows who is taking the drug). Most studies
have not used the same drug dosage used by athletes. Institutional safeguards
prohibit administration of high dosages of possibly dangerous substances to
human subjects. Subjects in research experiments seldom resemble accomplished
weight-trained athletes. Under these conditions, we must assess the results of
sound research studies, as well as clinical and empirical field observations, in
order to obtain a realistic profile of the use, effects on performance, and side
effects of these substances.
How Anabolic Steroids
Work
Male hormones, principally testosterone, are partially responsible for the
tremendous developmental changes that occur during puberty and adolescence. Male
hormones have androgenic and anabolic effects. Androgenic effects are changes in
primary and secondary sexual characteristics. These include enlargement of the
penis and testes, voice changes, hair growth on the face, axilla, and genital
areas, and increased aggressiveness. The anabolic effects of androgens include
accelerated growth of muscle, bone, and red blood cells, and enhanced neural
conduction.
Anabolic steroids have been manufactured to enhance the anabolic properties
(tissue building) of the androgens and minimize the androgenic (sex-linked)
properties. However, no steroid has eliminated the androgenic effects because
the so-called androgenic effects are really anabolic effects in sex-linked
tissues. The effects of male hormones on accessory sex glands, genital hair
growth, and oiliness of the skin are anabolic processes in those tissues. The
steroids with the most potent anabolic effect are also those with the greatest
androgenic effect.
Steroid
Receptors
Steroid hormones work by stimulation of receptor molecules in muscle cells,
which activate specific genes to produce proteins (see Figure 1). They also
affect the activation rate of enzyme systems involved in protein metabolism,
thus enhancing protein synthesis and inhibiting protein degradation (called an
anti-catabolic effect).
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Figure 1: How a Steroid Hormone Works |
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Heavy resistance training seems to be necessary for anabolic steroids to
exert any beneficial effect on physical performance. Most research studies that
have demonstrated improved performance with anabolic steroids used experienced
weight lifters who were capable of training with heavier weights and producing
relatively greater muscle tension during exercise than novice subjects. The
effectiveness of anabolic steroids is dependent upon unbound receptor sites in
muscle. Intense strength training may increase the number of unbound receptor
sites. This would increase the effectiveness of anabolic steroids.
Anti-Catabolic Effects Of Anabolic
Steroids
Many athletes have said that anabolic steroids help them train harder and
recover faster. They also said that they had difficulty making progress (or even
holding onto the gains) when they were off the drugs. Anabolic steroids may have
an anti-catabolic effect. This means that the drugs may prevent muscle
catabolism that often accompanies intense exercise training. Presently, this
hypothesis has not been fully proven.
Anabolic steroids may block the effects of hormones such as cortisol involved
in tissue breakdown during and after exercise. Anabolic steroids may prevent
tissue from breaking down following of an intense work-out. This would speed
recovery. Cortisol and related hormones, secreted by the adrenal cortex, also
has receptor sites within skeletal muscle cells. Cortisol causes protein
breakdown and is secreted during exercise to enhance the use of proteins for
fuel and to suppress inflammation that accompanies tissue injury.
Anabolic steroids may block the binding of cortisol to its receptor sites,
which would prevent muscle breakdown and enhances recovery. While this is
beneficial while the athlete is taking the drug, the effect backfires when he
stops taking it. Hormonal adaptations occur in response to the abnormal amount
of male hormone present in the athlete's body. Cortisol receptor sites and
cortisol secretion from the adrenal cortex increase.
Anabolic steroid use decreases testosterone secretion. People who stop taking
steroids are also hampered with less male hormone than usual during the "off"
periods. The catabolic effects of cortisol are enhanced when the athlete stops
taking the drugs and strength and muscle size are lost at a rapid rate.
The rebound effect of cortisol and its receptors presents people who use
anabolic steroids with several serious problems: (1) psychological addiction is
more probable because they become dependent on the drugs. This is because they
tend to lose strength and size rapidly when off steroids. To stave off
deconditioning, athletes may want to take the drugs for long periods of time to
prevent falling behind. (2) Long-term administration increases the chance of
serious side-effects. (3) Cortisol suppresses the immune system. This makes
steroid users more prone to diseases, such as cold and flu, during the period
immediately following steroid administration.
Psychological
Effects
Some researchers have speculated that the real effect of anabolic steroids is
the creation of a "psychosomatic state" characterized by sensations of well
being, euphoria, increased aggressiveness and tolerance to stress, allowing the
athlete to train harder. Such a psychosomatic state would be more beneficial to
experienced weight lifters who have developed the motor skills to exert maximal
force during strength training. Diets high in protein and calories may also be
important in maximizing the effectiveness of anabolic steroids.
Anabolic Steroids and
Performance
The effects of anabolic steroids on physical performance are unclear. Well
controlled, double blind studies have rendered conflicting results. In studies
showing beneficial effects, body weight increased by an average of about four
pounds, lean body weight by about six pounds (fat loss accounts for the
discrepancy between gains in lean mass and body weight), bench press increased
by about 15 pounds, and squats by about 30 pounds (these values represent the
average gains for all studies showing a beneficial effect). Almost all studies
have failed to demonstrate a beneficial effect on maximal oxygen consumption or
endurance capacity. Anabolic steroid studies have typically lasted six to eight
weeks and have usually used relatively untrained subjects.
Most changes in strength during the early part of training are neural:
increased strength is mainly due to an improved ability to recruit motor units.
Anabolic steroids affect processes associated with protein synthesis in muscle.
Studies lasting six weeks (typical study length) would largely reflect neural
changes and could easily miss the cellular effects of the drugs.
The gains made by athletes in uncontrolled observations have been much more
impressive. Weight gains of thirty or forty pounds, coupled with thirty percent
increases in strength, are not unusual. Such case studies lack credibility
because of the absence of scientific controls. However, it would be foolish to
completely disregard such observations because the "subjects" have been highly
trained and motivated athletes.Please see the articles on pharmacology of sport
and sports medicine in the countries of the former Soviet Union for more
information on anabolic steroids.
References
American Medical Association, Council on Scientific
Affairs. Medical and non-medical uses of anabolic-androgenic steroids. J. Amer.
Med. Assoc. 264: 2923-2927, 1990.
Bahrke, M.S., C.E. Yesalosk, and J.E. Wright.
Psychological and behavioural effects of endogenous testosterone levels and
anabolic-androgenic steroids among males: a review. Sports Med. 10: 303-337,
1990.
Buckley, W.E., C.E. Yasalis, K.E. Friedl, W.A.
Anderson, A.L. Streit, and J.E. Wright. Estimated prevalance of anabolic steroid
use among male high school seniors. J. Amer. Med. Assoc. 260: 3441-3445,
1988.
Rogozkin, V. Metabolism of Anabolic Androgenic
Steroids. Leningrad: Nauka, 1988.
United States Olympic Committee. USOC Drug Education
Handbook. Colorado Springs: USOC, 1989.
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