The study is a randomized controlled trial conducted in the Geriatrics Department of a tertiary hospital in Spain (Hospital Universitario de Navarra). Participants aged 75 years or older will be recruited within the first 48 hours of admission to the acute care ward. Eligible hospitalized patients will be randomly assigned to either the intervention or control group using permuted block randomization (block sizes of 8 and 10), with consideration of gender balance.

Data will be collected at four time points: baseline assessment, hospital discharge, 1 month, and 3 months post-discharge.

Inclusion criteria include age ≥75 years and admission to the acute care unit. Exclusion criteria include refusal or inability to provide informed consent, life expectancy <3 months or terminal illness (oncological or non-oncological), inability to complete follow-up, medical contraindications to exercise, severe neurocognitive impairment (GDS-FAST stage 7), or severe disability (Barthel Index <35).

General Objective

To determine whether an intervention consisting of a multicomponent physical exercise program based on strength, balance, and aerobic training can prevent hospitalization-associated disability in adults aged 75 years and older admitted for acute medical conditions, while improving functional and cognitive capacity.

Specific Objectives

1. To analyze and identify the patient subgroups that derive the greatest benefit from the intervention in order to optimize healthcare resource allocation (e.g., frail patients, patients with cognitive impairment, malnourished patients), and to characterize these subgroups.
2. To identify the sociodemographic, clinical, functional, and cognitive characteristics associated with greater responsiveness to the intervention, as well as the type of intervention that provides the greatest benefit.
3. To integrate clinical and molecular approaches through the assessment of epigenetic and inflammatory biomarkers, enabling the evaluation of parameters that have not previously been incorporated into studies of this kind.

Inclusion Criteria:

• Age equal to or greater than 75 years, admitted to the acute care unit for medical conditions.

Exclusion Criteria:

• Explicit refusal expressed verbally or refusal to sign the informed consent by the patient/main caregiver/legal guardian or inability to obtain it.
• Life expectancy of less than 3 months or terminal oncological or non -oncological disease.
• Inability to follow up.
• Inability to participate in a multicomponent exercise program.
• Medical contraindication to exercise.
• Major neurocognitive disorder at moderate to severe stage (GDS - Fast Reisberg 5-7).
• Moderate to severe disability (measured by the Barthel Index (BI <60)). Expected hospital stay of less than 6 days.