Men and women's muscles work differently — especially when it comes to strength and speed — and these differences matter more than getting older. Young men tend to have bigger, faster type I muscle...

Young men tend to have faster and bigger type I muscle fibers than young women, but this difference disappears in older adults and isn't seen in other fiber types — so the muscle differences between men and women depend on age and fiber type.

When it comes to leg muscle strength, the differences between men and women or young and older people are more about how the whole muscle works together—not just the individual muscle fibers. Things like nerves, hormones, or how muscles are coordinated might matter more than the fibers themselves.

When older adults (60+) do strength training, men and women gain muscle and get stronger in basically the same way—no big differences between the sexes.

One study with women showed a much bigger muscle growth difference than the others — all of which were only with men — suggesting sex might matter, but we need more studies to know for sure.

When older men and women over 60 do strength training, men tend to gain more total muscle mass than women, but when you account for their starting size, both sexes improve at about the same rate.