This study examines the age-related changes in skeletal muscle size and function over a 12-year period in a group of healthy, sedentary men. The initial evaluation was conducted in 1985-86 (T1), and nine participants were reevaluated in 1997-98 (T2). Key findings include: 1. **Muscle Strength**: Significant losses in isokinetic muscle strength were observed in the knee and elbow extensors and flexors, ranging from 20 to 30% at both slow and fast angular velocities. 2. **Muscle Cross-Sectional Area (CSA)**: Computerized tomography (CT) scans showed reductions in the CSA of the thigh, all thigh muscles, quadriceps femoris muscle, and flexor muscles, ranging from 12.5% to 16.1%. 3. **Fiber-Type Distribution and Capillary Density**: A significant decrease in the percentage of type I fibers was noted, while the mean fiber area remained unchanged. The capillary-to-fiber ratio was significantly reduced, indicating a decline in capillarization. 4. **Predictive Power**: Muscle strength at T1 and changes in CSA were independent predictors of strength at T2, accounting for 90% of the variability in strength at T2. The study highlights the significant loss in muscle CSA as a major contributor to the decrease in muscle strength with aging. These findings underscore the need for stronger exercise recommendations to prevent sarcopenia and early onset of disability in older adults.This study examines the age-related changes in skeletal muscle size and function over a 12-year period in a group of healthy, sedentary men. The initial evaluation was conducted in 1985-86 (T1), and nine participants were reevaluated in 1997-98 (T2). Key findings include: 1. **Muscle Strength**: Significant losses in isokinetic muscle strength were observed in the knee and elbow extensors and flexors, ranging from 20 to 30% at both slow and fast angular velocities. 2. **Muscle Cross-Sectional Area (CSA)**: Computerized tomography (CT) scans showed reductions in the CSA of the thigh, all thigh muscles, quadriceps femoris muscle, and flexor muscles, ranging from 12.5% to 16.1%. 3. **Fiber-Type Distribution and Capillary Density**: A significant decrease in the percentage of type I fibers was noted, while the mean fiber area remained unchanged. The capillary-to-fiber ratio was significantly reduced, indicating a decline in capillarization. 4. **Predictive Power**: Muscle strength at T1 and changes in CSA were independent predictors of strength at T2, accounting for 90% of the variability in strength at T2. The study highlights the significant loss in muscle CSA as a major contributor to the decrease in muscle strength with aging. These findings underscore the need for stronger exercise recommendations to prevent sarcopenia and early onset of disability in older adults.