Preventing the Loss of Muscle and Function in Hospitalized Older Adults

One third of independent older adults over the age of 65y will be hospitalized for an acute medical illness, injury, or operative procedure. Unfortunately, 50% of these older adults will experience functional decline during their hospital stay from the amount of time they are physically inactive and in bed. Following discharge, the functional deficits can persist for months and in many instances never return to pre-hospitalization levels thus compounding morbidity, health care costs and dying. A classic consequence of short-term bed rest in older adults is the significant loss in skeletal muscle mass which underlies the accelerated leg strength deficits. The investigator has shown that an important mechanism of skeletal muscle loss is the inability of nutrients to stimulate a normal muscle protein synthesis response; a process highly regulated by the mammalian target of rapamycin signaling pathway (mTOR) and amino acid transporters. Day to day maintenance of force generating muscle tissue is dictated by anabolic stimulation from muscle contraction and essential amino acid ingestion. Therefore, anabolic interventions such as neuromuscular electrical stimulation (NMES) and high quality protein supplementation that contains a high proportion of essential amino acids (whey protein) may be promising approach to maintain leg muscle mass and strength in hospitalized older adults and prevent the long term consequences of repeated periods of short-term physical inactivity. The purpose of this study is to test in older adults if the combination of NMES and protein supplementation is capable of preserving muscle mass and strength and maintaining muscle nutrient anabolic sensitivity during bed rest. The investigators current hypotheses are that daily NMES and protein supplementation during 5-days of bed rest in older adults will: 1) preserve lower extremity muscle mass and strength and 2) maintain muscle nutrient anabolic sensitivity as measured by mTOR signaling and amino acid transporter expression. The long term goal is to utilize this inpatient preventative therapeutic approach in a clinical setting in which muscle mass and strength deficits are profound (e.g., intensive care patients).