Let me just start by saying that this is the single most mis-understood compound in use for athletics and bodybuilding today. Most of the information out there is

First, lets plow quickly through some of the basics:

Clenbuterol (Clen) is a selective beta-2 agonist/antagonist and a bronchodilator. What this means, is that it stimulates your beta-2 receptors. And this in turn stimulates you (clen has stimulant effects which will make you feel….well…stimulated). All of this serves to increase your body temperature a bit, increase your basal metabolic rate, and decrease your appetite (Int J Obes Relat Metab Disord. 1994 Jun;18(6):429-33.). Clen also can decrease insulin sensitivity (Am J Physiol Endocrinol Metab. 2002 Jul;283(1):E146-53.).

Clen is a very effective repartitioning agent, and this is what it’s most often used for. What this means is that it will increase your ratio of Fat Free Mass (FFM) to Fat Mass, by decreasing your Fat and possibly increasing your FFM (J Appl Physiol. 2001 Nov;91(5):2064-70). Want me to quantify that a bit? In one study, horses given a semi-reasonable dose of clen (slightly over 1mcg/lb x2 a day) and excercised for 20mins, 3x a week ( I suppose they were Mentzer disciples) had significant decreases in %fat (-17.6%) and fat mass (-19.5%) at week 2, which was similar to Clen given to horses who didn’t excercise; however, the excercised group had a different FFM response, which significantly increased (+4.4%) at week 6. Week 6! Clen and clen+excercise produce roughly the same results for the first 2 weeks! Remember the old 2 weeks-on/2weeks-off schedule? It’s officially dead and buried. If you want the quasi-anabolic effect from the clen, it’ll take more than 2weeks on (6 weeks apparently). And in fact, since clen alone is similar to clen+excercise for those first 2 weeks...why would you ever use a 2on/2off protocol? Keep in mind that animal responses to beta-agonist/antagonists differ a bit from ours…but you get the picture. 2on/2off? Ha ha...