Scientists discover a hidden reason why muscles weaken with age

Scientists have uncovered a hidden defense mechanism in aging muscles that sacrifices strength to protect cells from damage. In mice, partially restoring a crucial molecule reversed signs of muscle wasting and prevented premature death, raising hopes for new treatments for age-related muscle decline. Muscles naturally become weaker as we get older, but scientists have discovered that some of the changes associated with aging may actually help protect muscle cells from damage. New research reveals why aging muscles shift toward a different type of muscle fiber and identifies a crucial molecule that could offer a new approach to treating muscle loss. Muscle tissue contains bundles of fibers with different functions.

Fast-twitch fibers produce powerful, rapid movements but fatigue relatively quickly. Slow-twitch fibers, by contrast, support sustained activity and contain higher concentrations of mitochondria, the cellular structures responsible for producing much of the energy muscles need. As people age, muscle strength declines and mitochondria become less efficient. Surprisingly, aging muscles also develop a greater proportion of slow-twitch fibers, even though these fibers depend heavily on the very mitochondria that are losing their ability to function. Researchers have observed similar changes in several conditions that cause muscle wasting. This raises an important question: Why would muscles increasingly rely on an energy-producing system that is becoming less effective? To investigate this