Older adults account for a large proportion of all hospital admissions and this will further rise. A hospital admission is a critical event for older adults. Hospitalized older adults are vulnerable making them prone for negative health outcomes after hospitalization, like loss of functional abilities. In response, comprehensive “senior-friendly hospital” (SFH)-programs aiming to improve hospital care were developed, however, it is unclear how effective these programs are. Sarcopenia or poor muscle status, in this thesis defined as low muscle strength and muscle mass, is highly prevalent in hospitalized older adults and associated with negative health outcomes, like readmissions. It is unknown if muscle strength and mass further deteriorate during and after hospitalization. Physical inactivity is an important determinant of sarcopenia. Routines of activities of daily living (ADL) and physical activity levels are disrupted during hospitalization resulting in hospitalized older adults being physically inactive, spending approximately 80% of the day in bed. Physical activity in hospitalized older adults is not routinely promoted by health care professionals and is challenging since it requires knowledge, and attitude and behavioral changes in patients and health care professionals. The aim of this thesis was to evaluate how care for hospitalized older adults can be improved focusing on 1) SFH-programs, their elements and effectiveness in improving care, 2) associations between poor muscle status and higher risks for negative health outcomes, and 3) aspects of physical activity promotion in older adults during hospitalization. In chapter 2, an overview was provided of ten SFH-programs introduced in various countries between 1990-2017. Elements of SFH-programs may improve care for hospitalized older adults, however, little was published on the effect of such programs on quality of care and patient satisfaction. In chapter 3, 4, and 5, the associations of poor muscle status and higher risks for negative health outcomes in hospitalized older adults were examined addressing the high prevalence of sarcopenia at admission and its association with long-term mortality, the association of lower muscle strength and muscle mass and being at risk of a higher cumulative number of geriatric conditions, and the results of a systematic review and meta-analysis of the change in muscle strength and muscle mass in older adults during hospitalization. In chapter 6, 7, and 8, aspects of how physical activity promotion can be effectuated in clinical practice were described. Evidence for the effect of physical interventions during hospitalization, for instance exercise programs, on lower risks for negative health outcome was found to be inconclusive. Considering the detrimental effects of physical inactivity in older adults during hospitalization, it remains important to pay attention to increasing general levels of physical activity during hospital stay. Important aspects to promote physical activity during hospitalization identified in this thesis are that 1) it takes a multidisciplinary approach, including nurses, physicians, physiotherapist, patients, and carers, with clear description of roles and responsibilities, and 2) barriers and enablers influencing physical activity promotion should be acknowledged to facilitate hospital staff and patients. Improving care for hospitalized older adults requires an integrated approach. Next to a general approach to increase awareness and physical activity promotion within the hospital, it is of importance to focus on a more tailored approach in implementing “senior-friendly” care which requires effort in identifying the right patients for the right interventions at the right time.