Efficacy of Nutritional Supplementation on Physical-activity Mediated Changes in Physical Functioning Older Adults at Risk for Mobility Disability (The VIVE2 Study)

Inclusion Criteria: 1. Male \& Female ≥ 70 yrs 2. Community dwelling 3. Short Physical Performance Battery ≤ 9 4. Willingness to be randomized and come to the laboratory for 6 months 5. Body Mass Index \< 35 6. Mini-Mental State Examination \>=24 7. Serum 25 (OH) D (22.5 -50 nmol/l) 8. Having obtained his/her informed consent 9. Able to complete 400 M walk within 15 minutes Exclusion Criteria: * • Acute or terminal illness; terminal illness with life expectancy less than 12 months, as determined by a physician * Current regular use (\> 1 per week) of high protein oral nutritional supplements (eg: Boost, Exceed etc…) * Current use of Vitamin D supplements, \>800 IU/day * Myocardial infarction in previous 6 months, symptomatic coronary artery disease, or congestive heart failure. * Upper or lower extremity fracture in previous 6 months. * Hemoglobin \< 10 g/dL, Estimated GFR \< 30 mL/min/1.73 m2 * Uncontrolled hypertension (\>150/90 mm Hg). * Neuromuscular diseases and drugs which affect neuromuscular function; severe progressive, degenerative neurologic disease * Hormone replacement therapy * Insulin-dependent diabetes mellitus * Milk protein allergy * Major surgery in the past 6 months (requiring general anesthesia) * Other significant co-morbid disease that would impair ability to participate in the exercise-based intervention, e.g. renal failure on hemodialysis, severe psychiatric disorder (e.g. bipolar, schizophrenia) * Excessive alcohol use (\>14 drinks per wk) * Participation in moderate intensity physical activity \> 20 minutes/week * Inability to communicate due to severe, uncorrectable hearing loss or speech disorder * Severe visual impairment (if it precludes completion of assessments and/or intervention) * Severe rheumatologic or orthopedic diseases, e.g., awaiting joint replacement, active inflammatory disease; wheelchair bound * Cancer requiring treatment in the past three years, except for non-melanoma skin cancers or cancers that have clearly been cured or in the opinion of the investigator carry an excellent prognosis (e.g., Stage 1 cervical cancer) * Severe pulmonary disease, requiring either steroid pills or injections or the use of supplemental oxygen * Severe cardiac disease, including NYHA Class III or IV congestive heart failure, clinically significant aortic stenosis, history of cardiac arrest, use of a cardiac defibrillator, or uncontrolled angina * Patient who cannot be expected to comply with treatment, as decided by the Principal Investigator and study physician. * Conditions not specifically mentioned above may serve as criteria for exclusion at the discretion of the clinical site Principal Investigator and/or study physician.