Sub-study: 'Validation of a portable bio-impedance analyzer in a population of older adults ≥ 70 years for the assessment of muscle mass and changes in muscle mass over time' A sub-study will be performed to investigate if the portable InBody-230 BIA correlate with DXA at single time points in 30 hospitalized older people ≥ 70 years, and to see if it is possible to track changes in LBM during the 12-week intervention. Total LBM, total fat mass, and percent LBM will be measured and compared as well as appendicular and trunk LBM. In addition, the reliability of the portable bio-impedance analyzer will be evaluated by assessing the degree of agreement between two subsequent measurements. In continuation of recruitment to the primary study, a subset of participants (n=30) will be asked if they want to participate in this sub-study, irrespective of their allocation in the main study. The measurements are going to be performed twice, while hospitalized and 12 weeks after discharge (± 5 days).