Despite the existing limitations and controversies regarding the definition of 
sarcopenia and its clinical consequences, the current scientific evidence 
strongly suggests that muscle decline is a primary determinant of the disabling 
process (and likely of other major health-related events). In fact, the muscle 
loss (in terms of mass as well as strength) occurring with aging has been 
growingly associated with mobility impairment and disability in older persons. 
Unfortunately, current evidence is mainly from observational studies. Times are 
mature to begin testing interventions aimed at modifying the sarcopenia process 
through the design and development of specific clinical trials. Considering the 
emergence of many promising interventions towards this age-related condition 
(e.g., physical exercise [in particular, resistance training], testosterone, 
antioxidant supplementations), the need for Phase II trial designs is high. In 
the present report, we discuss which are the major issues related to the design 
of Phase II clinical trials on sarcopenia with particular focus on the 
participant's characteristics to be considered as possible inclusion and 
exclusion criteria.