Clenbuterol increases lean muscle mass but not endurance in patients with chronic heart failure

Clenbuterol, a beta(2)-agonist with potent anabolic properties, has been shown to improve skeletal muscle function in healthy subjects, and in high doses, promotes cardiac recovery in patients. with left ventricular assist devices. In a small, randomized controlled study, we investigated the effect of clenbuterol on skeletal muscle function, cardiac function, and exercise capacity in patients with chronic heart failure. Clenbuterol was well tolerated and led to a significant increase in both lean mass and the lean/fat ratio. Maximal strength increased significantly with both clenbuterol (27%) and placebo (14%); however, endurance and exercise duration decreased after clenbuterol. Prior data support combining exercise training with clenbuterol to maximize performance, and on-going studies will evaluate this approach.