What's the first thing that comes to mind when you think about the words twitch and muscle? Spasms, perhaps. You'd hardly be alone in thinking that. But when it comes to fitness, it's most commonly ...

Everyone is familiar, at least hand-wavingly, with the distinction between slow-twitch and fast-twitch muscle-fiber types. The former are great for running marathons; the latter are ideal for ...

Your DNA might be giving you an edge or could be holding you back. The ACTN3 gene encodes the protein alpha-actinin-3, which is found almost exclusively in fast-twitch muscle fibers. These fibers are ...

Most fitness-minded people have probably heard of fast- and slow-twitch muscle fibers. However, the distinction can be somewhat mysterious, especially in the context of understanding how it relates to ...

San Francisco 49ers star tight end George Kittle's offseason mornings usually involve working out, and like many professional athletes, an extra energy boost is needed. Fast Twitch is his go-to ...

When you picture different athletes—marathon runners, gymnasts, and Olympic weightlifters, for example—you likely categorize them instinctively by their height, size, and build. But the differences in ...

Type IIb fast-twitch myofibers, known for their rapid contraction speed, are plentiful in small mammals but have largely diminished in humans. Researchers at the University of Tsukuba have discovered ...

Tsukuba, Japan—Muscle fibers, which constitute skeletal muscle, are classified into two main types: slow-twitch (Type I, red muscle) and fast-twitch (Type II, white muscle). Slow-twitch fibers are ...