What are creatine and androstenedione? Why are athletes using them?

Creatine (cree-ah-ten) is a nitrogen-containing compound found naturally in the body. About 95% of the body's total creatine is found in skeletal muscle. Two-thirds of the muscle's creatine is present in combination with phosphorus. It is this creatine phosphate that plays a critical role in the production of energy required for muscular contraction in short term exercise (when the demand for energy is greater than what can be supplied by aerobic means). The concentration of creatine is higher in fast twitch muscle fibers, which are better suited to forceful, short-term contractions. The energy production in short-term work appears to depend significantly on the amount of creatine in the cell (or fiber). Thus, the more creatine in the cell the greater the amount of more forceful short-term work that can be done. Athletes therefore may supplement their intake of creatine to boost the muscle stores of creatine. This may allow them to do more intense, short-term work, including working longer before fatigue causes cessation of work.

Androstenedione (andro-steen-die-own, sometimes called "andro" for short) is a steroid compound also found naturally in the body. In the body androstenedione is converted to the primary male sex hormone, testosterone, as well as to the primary female sex hormones, estrogens (estradiol and estrone). Plasma testosterone levels are typically more than 10 times higher for the average male than for the average female. Testosterone produces male-like (or androgenic) effects. In addition to facial hair and other masculine traits, testosterone may produce larger muscles through an anabolic effect. On its own, androstenedione has no muscle building effects. However, it can raise the body's testosterone levels for at least a few hours (possibly up to 24 hours). Whether this short-term rise in testosterone levels is sufficient to make any significant difference in muscle size, strength, or speed of contraction is controversial. However, when taken one-half hour to one hour before a workout, it is likely to be sufficient to allow the athlete to train harder and recover more quickly from exercise. An increase in intensity and/or frequency of training could further increase strength.

The primary reason athletes use creatine or androstenedione is to increase overall strength and/or the ability to do repetitive, intense, short-term work. Athletes in sports where strength, sprint speed, or the ability to do repeated and intense bouts of activity are the most likely to use these substances. Some of these sports might include football, hockey, and track and field events like the shot put, discus, javelin, and shorter sprints. Soccer and basketball players may also see benefits to increasing their size, strength, and ability to do repeated, intense, short-term bursts of activity. Wrestlers may desire the increase in strength and ability to do intense, short-term bouts of activity, but not the increase in body mass. There are also some special risks of using these substances when trying to lose weight. (See What are the short- and long-term risks?) Endurance sport athletes would probably benefit little or be hampered by increased body mass or strength. The added body mass could more than offset any increase in intense, short-term efforts. Therefore, wrestlers and those involved in endurance sports would probably be less likely to use creatine. In addition to high school athletes, those athletes involved in powerlifting, bodybuilding, and martial arts may also use these substances.