1. Muscle performance and physical function are associated with voluntary rate of neuromuscular activation in older adults Aging leads to weakness and poor mobility (for example, slower walking speed or difficulty rising from a chair), but the cause of weakness and the link between weakness and mobility is not fully understood. Because there are large differences in health status and physical activity levels between older adults, it is difficult to determine if weakness is normal with healthy aging or if it happens because of other diseases. The way muscles generate force may be dependent in part on how well the nervous systems can turn on or activate the muscles. It is important to determine whether poor nervous system activation of muscles occurs in all older adults or just some, and whether this issue might contribute to poor mobility. ARS-funded researchers from Tufts University in Boston, MA found that muscle activation (a measure of the nervous systems ability to make muscles move) was slower in older adults with limitations in their mobility but not healthy older adults. We also found that women have slower rates of muscle activation than men. The slowness of muscle activation was related to the subject’s muscle strength or how much weight a person can lift. Our results suggest that the rate of muscle activation is a good indicator of problems in the nervous system that might contribute to poor mobility in older adults.