Anabolic steroids increase muscle size and strength through various mechanisms, including an increase in muscle protein synthesis and a significant decrease in muscle catabolic processes. Psychological effects also play a role. The increased aggression often noted with steroid use fosters more intense, heavier training. One aspect of steroids not previously examined is how they affect the internal structure of muscles; that is, the way muscle fibers contract.
A group of researchers who had previously studied the effects of combining testosterone enanthate injections with weight training for 12 weeks recently published a new study.1 In the earlier study subjects received an injection of testosterone enanthate that was 3.5 milligrams per kilogram (2.2 pounds) of bodyweight. That amounts to 315 milligrams of testosterone weekly, a conservative amount for a typical bodybuilder. Another group got a placebo injection. As expected, the steroid group made considerably greater gains in muscle size and strength.
The new study, which also took place over 12 weeks, involved 10 of the same subjects who used the same amount of testosterone enanthate injections and engaged in weight training; another group got a placebo. The researchers focused on structural changes in the triceps muscles in the two groups, which were both training hard. Strength gains were measured by increases in one-rep-maximum poundages on the bench press.
Those taking the testosterone injections made significantly greater strength gains than those in the drug-free group. The steroid group also showed increased muscle pennation, which refers to the direction in which individual muscle fibers run between the origin and insertion points of a muscle. Muscle pennation determines the direction of muscular contraction, and the increased pennation in the steroid group increased muscle force through more efficient contractions. Those in the drug-free group did not experience that muscle pennation change, though changes they did show led to a finding of no significant difference in muscle thickness between the two groups, which would surprise many people.
The major discovery of the study was that even conservative doses of anabolic steroids appear to promote changes in a muscle's internal architecture, which results in greater muscle contractile force'and thus greater muscular strength'when combined with training.
Clenbuterol continues to be a popular drug for bodybuilding purposes. It's classified as a beta-2 agonist drug, meaning that it works by interacting with beta-adrenergic cellular receptors. There are various types of adrenergic receptors. Some are thought to play a role in mobilizing bodyfat by promoting the release of fat contained in fat cells when certain substances activate them. One such substance is epinephrine, an adrenergic hormone synthesized in the adrenal glands.
Beta-2 agonist drugs such as clenbuterol mimic the effects of epinephrine. Among other functions, beta-2 cell receptors, when activated, cause the dilation of bronchial tubes, thus helping to control respiratory diseases, including asthma and chronic bronchitis.
Even so, you cannot obtain a prescription for clenbuterol in the United States, although it is available in several European countries, including Belgium, Spain and Germany, as well as in Mexico. The U.S. Food and Drug Administration never approved clenbuterol for use in this country for several reasons. The main one is that it offers no benefits over presently approved drugs for treating asthma but does have a greater potential for side effects. The longer time it takes for the body to metabolize clenbuterol increases the chances of side effects. It's likely also why major drug companies in the U.S. have not shown interest in marketing clenbuterol for human use. Its higher side-effect profile could lead to legal repercussions.
Pharmacokinetic studies show that clenbuterol is 70 to 80 percent bioavailable when taken orally. It has an elimination half-life of 25 to 39 hours, meaning it takes that long for the body to metabolize and eliminate half the original dose. That's in contrast to the most prescribed asthma drug in the U.S., albuterol, which has a half-life of 3.5 to six hours. The typical suggested dose for therapeutic use of clenbuterol'bear in mind that it's not legally approved for such use'is five to 40 micrograms orally, taken twice daily. Bodybuilders typically use four to eight 20-microgram tablets daily. When clenbuterol is taken orally, peak blood levels occur within two to three hours, although the drug stays in the body far longer.
Unlike most other beta-2 agonist drugs, clenbuterol has greater effects on body composition, which explains its popularity with athletes, particularly those seeking to lose bodyfat rapidly. Animal studies with a variety of species beginning in 1978 showed that clenbuterol offers a unique repartitioning effect, meaning it promotes bodyfat loss while simultaneously increasing muscle mass. The muscle mass primarily affected is the type 2B muscle fibers, which are most prone to hypertrophy, or growth. What isn't often discussed about the muscle-growth properties of clenbuterol is that the amounts given to animals that showed the effect were 6,000 times the maximum human therapeutic dose.
Clenbuterol in the doses provided to animal subjects would cause severe problems, even death, in any human foolish enough to take it, but what happens if you take doses smaller than those given to animals yet greater than what's given for medical treatment? That's what human athletes do when using clenbuterol'illegally'to foster an increase in lean mass and significant fat loss.
Although now banned for use in livestock, clenbuterol used to be popular in Europe for changing animal body composition. Over the years the medical literature has documented what happened when people in Europe unknowingly ate clenbuterol-tainted meat products. The clenbuterol level was high because the amount needed to promote growth in animals averaged five to 10 times the therapeutic doses. In addition, clenbuterol is heat stable and survives cooking procedures, so humans easily take it in by eating meat containing the drug.
The amount of clenbuterol needed to cause a food-poisoning effect is estimated to be 0.1 micrograms per gram of food. That means a single beef meal containing clenbuterol-tainted beef would give you far more than doses used for bodybuilding purposes. The drug concentrates in certain organs of animals, such as lungs, liver and kidneys, and eating those particular parts of beef leads to greater side effects. The effects of clenbuterol-contaminated beef occur after someone has eaten about 100 to 200 grams of food, which is equivalent to five times the therapeutic drug dose.2
People who take 60 to 80 micrograms of clenbuterol complain of headaches and nervousness.3 Studies show that about 15 percent of people taking even suggested therapeutic doses of 20 to 40 micrograms also experience headaches. For bodybuilders the typical dose is 60 to 120 micrograms, although reports have surfaced of some using 400 micrograms or more a day. Usual side effects include fast heartbeat, muscle tremors and a cramping sensation in the hands due to mineral electrolyte shifts from the blood into cells.
One case involved a 29-year-old male bodybuilder who took 1,575 micrograms of clenbuterol daily for 1 1/2 months. He showed various side effects, as would be expected from such a relatively massive dose: enlargement of the left ventricle, or pumping chamber, of the heart, an effect that also occurs with regular exercise or steroid use, rapid heartbeat while training, and a left ventricular ejection fraction of 40 percent, meaning his heart was pumping blood at less than half normal efficiency.
Clenbuterol causes heart enlargement in animals and humans. How it does that isn't known, although some scientists suggest it may be a compensatory reaction to muscular growth. Other possibilities include chemical reactions induced by clenbuterol, since the heart enlargement related to clenbuterol is blocked by other drugs, including aspirin and beta-blocking drugs.
The problem with clenbuterol with regard to cardiovascular health relates to its structural similarity to epinephrine, which stimulates the heart. In fact, an entire category of drugs'beta-blockers'works by preventing the cardiac-stimulating effects of epinephrine. When excessive doses of beta-adrenergic drugs like clenbuterol are used, the heart can be overstimulated, resulting in heart rhythm disturbances. That effect is intensified because clenbuterol lowers blood levels of potassium and magnesium, minerals that help maintain normal heart rhythms. Clenbuterol is particularly dangerous when used under hot-weather exercising conditions, since it may induce elevated body temperature. When combined with dehydration, which can occur if you don't drink enough fluids, serious or even fatal heart problems can result. The same side effects, by the way, can also occur with overdoses of ephedrine.
A recent case shows what happens when a person takes too much clenbuterol.4 A 28-year-old woman showed up at a hospital emergency room complaining of tremors, palpitations and vomiting. She told attending doctors that she had tasted a fingertip quantity of an unknown white powder (can you imagine that in an era of anthrax?) in an attempt to 'identify it.' She began to feel sick within an hour. When she asked her boyfriend what was in the powder, he told her that it was clenbuterol, which he used for bodybuilding purposes.
She was treated with various drugs to help block the effects of clenbuterol on her heart and was given intravenous potassium to treat her lowered blood potassium level. Even after 10 hours in the emergency room she showed symptoms but opted to leave despite medical advice to the contrary. She returned to the hospital seven hours later, denying that she had again 'tested' the clenbuterol powder. The doctors again gave her medication to slow her raging heartbeat, but again she decided to leave.
In other reported cases of clenbuterol overdose, symptoms began within 15 minutes to six hours after ingestion, lasting for 90 minutes to six days. In the case described above, the patient also had hyperglycemia, a common side effect of beta-agonist drugs, which led to a decreased blood level of phosphate that resolved without treatment.
One often-overlooked property of clenbuterol is that it apparently interferes with exercise-induced gains, especially endurance. A recent study involving horses, for which clenbuterol is legal in the U.S. to treat various lung disorders, found that even therapeutic doses favorably influenced body composition in the horses by promoting fat loss while building muscle.5 The fat-loss effect lasted only two weeks and was attributed to a down regulation, or loss of activity, of beta-adrenergic cell receptors induced by clenbuterol. That effect also occurs in humans, meaning the fat-mobilizing effect of clenbuterol is extremely short-lived, averaging two to three weeks.
Another interesting finding of the horse study that confirms earlier studies was that horses given clenbuterol without exercise showed increased fat loss and muscle mass by the two-week point. But the horses that got clenbuterol and also exercised (three days a week of running) didn't show lean mass gains until the sixth week. The study authors concurred with previous observations that combining clenbuterol with exercise appears to impede the anabolic effect, although exactly how that happens remains uncertain.
As noted, clenbuterol fails to work within a short time due to down regulation or a decrease in activity of the beta-adrenergic cellular receptors.
Exercise, especially aerobic exercise, is known to maintain the activity of adrenergic cell receptors. Theoretically, combining clenbuterol and aerobics may make the drug work longer in terms of fat loss, but scientists don't know exactly how much exercise is required for that extended effect. They do know that any exercise derails clenbuterol's anabolic, or muscle-building, effects.
That is a moot point, however. As the animal studies demonstrate, only doses that would clearly be toxic to humans promote muscle growth in animals. The horse study discussed above, in which therapeutic doses of clenbuterol led to favorable body composition changes, involved a dose of 2.4 micrograms per kilogram of bodyweight. That equals 216 micrograms in a 200-pound man, or about 11 tablets of clenbuterol daily'an amount likely to lead to intolerable side effects in most people.
Finally, a recent study showed that when rats bred to be obese and markedly insulin-resistant were intubated with one milligram per kilogram of clenbuterol daily for five weeks, they showed decreased insulin resistance combined with heightened glucose tolerance.6 That scenario suggests clenbuterol would help prevent diabetes. The researchers said that clenbuterol induced loss of fat and increased muscle tissue, both of which increase insulin efficiency. It's hard to see any point in human use, however, since the rats were given one gram of clenbuterol per kilogram of bodyweight. Clenbuterol is provided in microgram amounts in drugs, and one milligram equals 1,000 micrograms. So the dose given to the rats would not likely have similar effects in humans. Insulin resistance would be the least of the problems experienced by any human taking that amount.
1 Blazevich, A.J., et al. (2001). Effect of testosterone administration and weight training on muscle architecture. Med Sci Sports Exerc. 33:1688-93. 2 Kuiper, H.A., et al. (1998). Use of beta-agonists: European community. J Anim Sci. 76:195-207.
3 Whitsett, T.L., et al. (1981). Pulmonary and neuromuscular effects of clenbuterol and terbutaline compared with placebo. Br J Clin Pharm.
4 Hoffman, R.J., et al. (2001). Clenbuterol ingestion causing prolonged tachycardia, hypokalemia and hypophosphatemia with confirmation by quantitative levels. Clin Toxicol. 39:339-44.
5 Kearns, C.F., et al. (2001). Chronic administration of therapeutic clenbuterol acts as a repartitioning agent. J Appl Physiol. 91:2064-2070.
6 Pan, S.J., et al. (2001). Effects of clenbuterol on insulin resistance in conscious obese Zucker rats. Am J Physiol Endocrinol Metab. 280:E554-E561.