The Study of Muscle Mobility and Aging (SOMMA) is a cohort uniquely designed to identify fundamental age- related pathways contributing to outcomes that are important to older people. SOMMA2 extends SOMMA1, which tests the paradigm that properties of muscle, including muscle mitochondrial energetics, predict the onset of objective mobility disability. SOMMA1 established a rich repository of muscle tissue, blood, and phenotyping, to expand research to other pathways and clinical endpoints. SOMMA2 adds 650 new participants to increase its diversity and provide sufficient power to test whether biological pathways predict our composite outcome of ADL disability, dementia, or death. SOMMA2 will also gather unprecedented longitudinal data with repeat muscle biopsies to identify changes in biological pathways in muscle tissue that are associated with age-related changes in muscle power and cardiopulmonary fitness (VO2 peak). SOMMA2 will evaluate essential and interrelated biological pathways of aging: 1. Mitochondrial energetics in muscle and blood. 2. Somatic DNA damage and insufficient repair, DNA mutations and clonal hematopoiesis. 3. Increasing oxidative stress and modification 4. Cell senescence and inflammatory senescence associated secretory phenotype. SOMMA2 will also use longitudinal transcriptomics in muscle to discover biological pathways that influence change in power and fitness. SOMMA2 will also employ single nucleus snRNA seq to reveal how different muscle-resident cell types, and how differential gene expression across cell types, with contribute to muscle power and fitness. SOMMA has already been very productive and has become a major resource for investigators, particularly young scientists to provide career development opportunities. The data and specimens from SOMMA2 will be a unique resource fueling translational research for decades to come.