Here are some studies about vitamin D and sarcopenia:
Conclusion: A study of 976 elderly people found that those with higher vitamin D levels had higher handgrip strength.
Conclusion: This three-year study of 979 elderly people found that those with lower vitamin D levels demonstrated an inferior physical performance (in walking and standing) and suffered a faster decline in physical performance compared to those with higher vitamin D levels.
Low-Dose Vitamin D Prevents Muscular Atrophy and Reduces Falls and Hip Fractures in Women After Stroke: A Randomized Controlled Trial (2005)
Conclusion: A two-year study of 96 elderly, female stroke victims found that those supplementing with 1000 IU of vitamin D2 daily suffered fewer falls and hip fractures, demonstrated improved muscular strength, and enjoyed an increase in the number and size of type 2 muscle fibers compared to the placebo group.
Higher 25-Hydroxyvitamin D Concentrations are Associated with Better Lower-Extremity Function in Both Active and Inactive Persons Aged > or =60 y. (2004)
Conclusion: In an experiment involving people over the age of 60, those with higher vitamin D levels demonstrated a superior ability to walk and ability to transition from a sitting to standing position.
Low Vitamin D and High Parathyroid Hormone Levels as Determinants of Loss of Muscle Strength and Muscle Mass (Sarcopenia): The Longitudinal Aging Study Amsterdam (2003)
Conclusion: This 3-year study involving 1,008 elderly people found that those with lower vitamin D levels suffered a faster rate of muscle mass loss and muscle strength loss (sarcopenia) compared to those with higher vitamin D levels.
Conclusion: Vitamin D levels, arm strength, and leg strength were tested in 269 elderly people over a 6-month period. Women with low vitamin D levels were found to have significantly weaker arm and leg strength.
Neuromuscular and Psychomotor Function in Elderly Subjects who Fall and the Relationship with Vitamin D Status (2002)
Conclusion: Vitamin D-deficient elderly people were found to have “slower functional performance, weaker quadriceps, slower reaction times, and worse stability” compared to those with higher levels.
Conclusion: The vitamin D levels of 319 elderly people were tested along with their leg extension power. In both the men and the women, vitamin D levels were strongly correlated with their leg extension power.