People may lose 20 to 40 percent of their muscle -- and, along with it, their strength -- as they age. Scientists have found that a major reason people lose muscle is because they stop doing everyday activities that use muscle power, not just because they grow older.
Update Date 1/5/2016
Updated by: Joseph V. Campellone, MD, Division of Neurology, Cooper University Hospital, Camden, NJ. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.