Human muscle composition is more variable and heterogeneous than in rodents, making direct comparisons of fiber type differences across studies more complex.

“Human muscle is much more variable, heterogeneous. And so elite endurance athletes tend to have a much higher preponderance of slow twitch muscle fibers, 70, 80%. Elite strength athletes, power lifters, tend to have much higher preponderance of fast twitch muscle fibers. But the vast majority of us are walking around, somewhere around 50-50, 40-60.”