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ANABOLIC-ANDROGENIC STEROIDS: Mechanism of Action and Effects on Performance
Thomas D. Fahey
Exercise Physiology Laboratory
California State University, Chico
Chico CA 95929 USA

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

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).

Figure 1: How a Steroid Hormone Works

How a Steroid Works

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.


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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