A longitudinal study of muscle strength, quality, and adipose tissue infiltration in older adults found that muscle strength decreases more significantly than muscle mass over five years. The study, involving 1678 participants, showed that men experienced a 16.1% loss of muscle torque (MT), while women had a 13.4% loss. Adjusted annualized decreases in MT were 2–5 times greater than the loss of muscle cross-sectional area (CSA). Despite some increases in muscle CSA with weight gain, MT did not improve, indicating a decline in muscle quality (MQ). Weight loss was associated with a decrease in subcutaneous fat (SF), while weight gain was linked to an increase in SF. Both men and women showed an age-related increase in intermuscular fat (IMF), regardless of weight changes. The study highlights that aging is associated with increased IMF, which may contribute to muscle weakness and metabolic issues. These findings suggest that muscle quality declines with age, and that IMF accumulation is a significant factor in age-related muscle dysfunction. The study also found that IMF increases were more pronounced in men, particularly those with diabetes. The results emphasize the importance of monitoring muscle composition and function in older adults to prevent age-related decline in physical function.A longitudinal study of muscle strength, quality, and adipose tissue infiltration in older adults found that muscle strength decreases more significantly than muscle mass over five years. The study, involving 1678 participants, showed that men experienced a 16.1% loss of muscle torque (MT), while women had a 13.4% loss. Adjusted annualized decreases in MT were 2–5 times greater than the loss of muscle cross-sectional area (CSA). Despite some increases in muscle CSA with weight gain, MT did not improve, indicating a decline in muscle quality (MQ). Weight loss was associated with a decrease in subcutaneous fat (SF), while weight gain was linked to an increase in SF. Both men and women showed an age-related increase in intermuscular fat (IMF), regardless of weight changes. The study highlights that aging is associated with increased IMF, which may contribute to muscle weakness and metabolic issues. These findings suggest that muscle quality declines with age, and that IMF accumulation is a significant factor in age-related muscle dysfunction. The study also found that IMF increases were more pronounced in men, particularly those with diabetes. The results emphasize the importance of monitoring muscle composition and function in older adults to prevent age-related decline in physical function.