182 encourage research on sarcopenia. However, the reasonable uncertainties (derived from exploring a novel field and the exponential acceleration of scientific progress) require the adop- tion of a cautious and comprehensive approach to the subject. 1 Introduction One of the most recognized changes in body composition with senescence is the loss of skeletal muscle mass. This loss occurs even among physically active older persons, and it was originally termed “sarcopenia” for the Greek words “flesh” and “loss” [1]. The age-related loss in skeletal mus- cle mass is associated with substantial social and economic costs and is characterized by impairments in strength, limita- tions in function, and ultimately physical disability and insti- tutionalization [2–4]. In consideration of the increased M. Aubertin-Leheudre Départment de kinanthropologie, Université du Quebec, Montreal, Canada J. M. Cedarbaum Clinical Research Operations, Neuroscience & Neuromuscular Disorders, Cytokinetics Inc., South San Francisco, CA, USA M. Zamboni Department of Medicine, University of Verona, Verona, Italy C. C. Sieber Institute for Biomedicine of Aging, Friedrich-Alexander- University Erlangen-Nürnberg, Nuremberg, Germany D. Laurent Novartis Institutes for Biomedical Research, Basel, Switzerland W. J. Evans Muscle Metabolism DPU, Metabolic Pathways CEDD, GlaxoSmithKline, Research Triangle Park, NC, USA R. Roubenoff Musculoskeletal Translational Medicine, Novartis Institutes for Biomedical Research, Cambridge, MA, USA J. E. Morley University School of Medicine and GRECC, VA Medical Center, St. Louis, MO, USA M. Cesari (*) Institut du Vieillissement, Gerontopôle, Université de Toulouse, 37 Allées Jules Guesde, 31000 Toulouse, France e-mail: macesari@gmail.com J Cachexia Sarcopenia Muscle (2012) 3:181–190 awareness of this syndrome and the continued rapid develop- ment of therapeutic strategies to slow or reverse sarcopenia, the International Working Group on Sarcopenia was convened to address issues related to the successful conduct of clinical trials in this area [5]. This task force, consisting of geriatricians and scientists from academia and industry, met again in Tou- louse, France in June of 2011 to discuss the current state of the art in the development of biomarkers to be utilized in clinical trials on sarcopenia. The purpose of this meeting was to gain an understanding of the currently available parameters that could be utilized in clinical trials of sarcopenia and to discuss future research needs in this area. Specific topics that were addressed include: review of current consensus definitions of sarcopenia, the importance of muscle performance and qual- ity, biomarkers in other clinical states and chronic diseases, potential biomarkers for sarcopenia, applications in clinical trials, and recommendations for future studies. 2 Definition of sarcopenia Since the advent of the term “sarcopenia” in 1989, there has been a dramatic increase in publications in this area and clinical interest in this condition [6]. Originally described as the age-related decrease in skeletal muscle mass [7], until very recently, there has been a lack of consensus on the operational definition of sarcopenia without clinically ap- propriate correlates for this syndrome. In the past 2 years, a number of academic societies have put forward operational definitions of sarcopenia [8–11]. Although each consensus definition has some distinct features, there is general agree- ment among these groups on the definition of sarcopenia. A summary of consensus sarcopenia definitions is presented in Table 1. The characteristics of sarcopenia highlighted in these reports include an objective measure of muscle or fat free mass using dual energy X-ray absorptiometry (DXA) or computed tomography (CT), a reliable measure of muscle strength, and/or an objective test of physical functioning. Although the sequence of events and specific recommenda- tions somewhat differ, the general approaches proposed require that patients be identified with measured deficits in physical function for which sarcopenia may be the cause and subsequently quantification of muscle strength and mass to definitively confirm the diagnosis. 3 Definition of a biomarker A biomarker is defined as “a characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention” [12]. Hence, biomarkers support the diagnosis, facilitate the tracking of changes