This randomized controlled trial investigated the effects of a four-week moderate-intensity resistance training program on diaphragm thickness, hepatic fat density, and health-related quality of life in healthy community-dwelling older men aged 60-75 years. Thirty participants were randomly assigned to a resistance training group or control group. Diaphragm thickness and hepatic attenuation were assessed using non-contrast computed tomography, and quality of life was evaluated using the SF-12 questionnaire. The primary outcome was change in diaphragm thickness. Secondary exploratory outcomes included hepatic fat density and SF-12 physical and mental health scores.

Aging is associated with progressive decline in respiratory muscle morphology, metabolic health, and perceived quality of life. While resistance training is well established for peripheral muscle adaptation, its short-term effects on diaphragm morphology and hepatic tissue density remain insufficiently investigated.

This randomized controlled pre-test-post-test trial enrolled 30 healthy men aged 60-75 years. Participants were randomly allocated (1:1) to:

Resistance Training Group (RT) Control Group (CON) The RT group completed a supervised moderate-intensity resistance training program three times per week for four weeks (30-40 minutes/session, RPE 12-15). The control group maintained usual daily activities.

Primary Outcome:

Change in diaphragm thickness (mm) assessed by non-contrast CT

Secondary Outcomes (Exploratory):

Hepatic attenuation (Hounsfield Units) via CT SF-12 Physical Health Score SF-12 Mental Health Score The study was approved by the Hitit University Scientific Research Ethics Committee (2025/0464) and conducted according to the Declaration of Helsinki.

Inclusion Criteria:

• Male
• Age 60-75 years
• Community-dwelling and functionally independent
• No structured exercise program in past 6 months
• No musculoskeletal injury in past 6 months
• Ability to provide written informed consent
• Stable neuropsychological status

Exclusion Criteria:

• Chronic liver disease
• Uncontrolled cardiovascular or pulmonary disease
• Recent respiratory infection
• Use of medications affecting muscle or liver metabolism (e.g., systemic corticosteroids, anabolic agents, hepatotoxic drugs)
• Participation in structured exercise or respiratory training within past 6 months
• Unstable thyroid hormone replacement therapy

Individual participant data will not be shared due to the absence of prior consent for data sharing and the potential risk of re-identification in a small, single-center sample. Only aggregate results will be disseminated.