Is it possible I just have no slow-twitch muscles?

Question

I was very good at sports and played nine years of football and college lacrosse, among other sports, but could never really run decent distance times. Not even close. I still run today just for cardio, but am not breaking any records. I have a build that's more like a football fullback, with giant thighs, and can lift an incredible amount of weight with my legs -- just the distance running thing was never my forte.

Could it be that I just have few slow-twitch muscle fibers? Could those muscles be developed, or should I just forget about the idea of ever running a respectable 2-mile time?

Answer 1

That is not possible at all.  You do have slow-twitch, just like everyone else.  Everyone has slow-twitch and fast-twitch muscle, but how much each person has varies depending on the level and type of consistent activity throughout their lifetime.

It is easily possible that you have more well-developed fast-twitch muscle than slow-twitch muscle, especially since you said you played football and lacrosse, which both encourage quick, explosive power.  You can build up the necessary muscle to run quickly, you just need to work hard at it consistently for a long time, like you did with football/lacrosse.  The activities that you engage in as you develop, especially during your teenage years, have a dramatic effect on how you will end up being shaped.  For example my brother played baseball and lifted during high school and college, but I ran track/cross country.  Now he is built 'bigger' and I have a more slim build.  It's also easier for him to pick up lifting again and easier for me to pick up running again after a break, due to muscle memory.

Answer 2

No one has just slow or just fast twitch muscle fibers.

You can develop the muscles you have, but you are limited to what you can do.

That is why some are better at different races than others.

Your size is going to limit your ability at distance running.

You can still run a respectable 2 mile time, just not an elite time.