Clenbuterol reduces soleus muscle fatigue during disuse in aged rats

High levels of clenbuterol have been shown to preserve muscle mass and func tion during disuse. In this study we report that a low dose of clenbuterol (10 mug/kg per day) lessened the loss of in situ soleus muscle isometric fo rce normalized to wet muscle weight (P-o/g wet weight) by 8% and reduced is ometric fatigue by similar to 30% in senescent rats after 21 days of hindli mb suspension (HS). Clenbuterol did not reduce the loss of relative force i n the soleus of adult rats or the plantaris of old or adult rats. Furthermo re, clenbuterol failed to improve muscle force or isometric fatigue in the soleus of adult rats or in the plantaris of either age group after HS. We c onclude that low levels of clenbuterol reduce muscle fatigue in slow muscle s during disuse and this beta -agonist may also have therapeutic value for reducing fatigue in slow muscles (e.g., postural muscles) in the elderly du ring disuse. (C) 2001 John Wiley & Sons, Inc.