Do ZMA and tribulus terrestris really work for bodybuilders?
Justin Leonard: Both ZMA (zinc magnesium aspartate) and tribulus (a plant/herb) supplements claim to boost testosterone production. The following is a link (PDF file) to a study which renders ZMA as pretty much a useless supplement. The researchers in this study found that ZMA had no significant effect on strength or endurance in trained/fit subjects. Here is a study on tribulus terrestris (PDF file). In this study, scientists administered tribulus to a given number of subjects over a four-week period and found that it had no effect on serum testosterone levels. In a similar study, researchers concluded that tribulus supplementation had no effect on the bodyweight, body composition, strength, or endurance of trained subjects. I should also point out that although ZMA and tribulus may be ineffective for testosterone production, they have been shown to be useful for other things, including treatment of impotence, hypertension, high cholesterol, and more. Sometimes, zinc and tribulus supp
