Morpheus--great points. Not too many huge asthmatics walking around made me LOL. MCat is also quite correct here. I did not find any human studies in a rather exhaustive search of medline. Mostly rats, some chickens and dogs. Animal models do have applications to humans, of course, but many studies that show a strong effect on one species may show no or some opposite effect on another. Granted, we as humans seem to have no problem injecting vials of gear with a silhoutte of a cow or horse on the label
Collectively, studies do seem to show that, in rats, clen does have an anabolic, or more accurately, an anti-catabolic, effect on certain muscle groups. Of note, the greatest effects are usually seen in models where disuse atrophy has been induced by hindlimb unloading. For example, one study showed enhanced hybrid-fiber types in rat soleus after 14 days of hindlimb unloading, with a complex remodelling of muscle types that promoted a combination of both slow and fast myosin heavy chain isoforms within individual fibers (Piquet et al. Can J Physiol Pharmacol 2004). These studies suggest a role in treatment of (or prevention of) disuse atrophy associated with certain disease states. The question remains, then, is whether an effect is seen in loaded muscle as well.
Indeed, this effect has been shown to be mediated through an inhibitory effect on the ubiquitin-proteasome pathway. Upregulation of this pathway has been demonstrated in rats randomized to hindlimb unloading as well as those allowed to weightbear normally (Yimlamai et al J Appl Physiol 2005). Both groups demonstrated hypertrophy of all muscle groups tested, especially in fast twitch muscles. Of note, this effect was not mediated through local production of IGF-1. Similar findings have been observed in canine cardiac muscle (Sharif et al J Surg Res 2005).
Sounds promising so far, right?
Well, the information also gets a little fuzzy.
In another study, chronic administration of clen in albino mice did increase body mass and anabolic effect on gastroc and cardiac muscle. However, histopathologic sections demonstrated extensive collagen infiltration and areas of myonecrosis (muscle death) in the subendocardium. Not good... (Physiol Res 2005). But wait, there' more: High doses of clen have been shown to induce this necrotic myocyte death in the heart as well as slow-twitch skeletal muscle in the rat as well. In male Wistar rats subjected to a single subcutaneous dose of clen, myocyte (muscle cell) apoptosis (i.e. "cell-death") was first detected only 2hrs after administration, peaking at 4 hrs. The effect was dose- dependent (Burniston et al, Muscle Nerve 2005). There are a host of related studies suggesting exactly the same thing.
Oh, and one more interesting finding: In broiler chickens, clen caused a downregulation of testicular androgen receptors (Shiavone et al, J Anim Physiol Anim Nutr 2004).
The only human study I came across described the death of a teenage bodybuilder using clen. Death occurred by myocardial infarction.
So, you will have to decide for yourself whether clen is worth it. Personally, I prefer eating clean and doing some aerobics, but what the hell do I know
