How muscles work in older people

As people get older, their muscles change in a way that makes certain muscle parts bigger and faster-acting, which is like rewiring how the muscles work.

This research suggests that in both younger and older people, the way muscles activate their fibers follows the same basic rule: smaller muscle fibers get called into action before bigger ones. This pattern stays consistent as we age.

Your muscles use smaller, less powerful fibers first when you start moving, and only bring in the bigger, stronger fibers when you need more power or get tired.