Advertisement While doing so, you might ask yourself, “Why do some athletes excel in endurance sports while others in speed or strength sports?” It’s more likely you’ll say something like, “I didn’t know trampolining was an Olympic sport!”
An athlete’s muscle fiber contracts in a way similar to a tug-of-war. With each muscle in the human body composed of thousands of muscle fibers, that’s a lot of simultaneous tug-of-wars. A muscle fiber is composed of many different proteins; two of the most prominent are myosin and actin. Myosin, in our sporting example, are the people pulling on the rope while actin is the rope itself.
When we want to produce a large amount of force, we can put more people on the rope (actin) or we can have our people (myosin) pull more vigorously. Certain types of myosin can pull really hard and fast on the rope — these are known as fast twitch fibers — but they also tire out very quickly. Slow twitch fibers, by contrast, can’t pull as hard, but they can keep it up for a long time. We can’t really change how many of each of these fibers we have — it’s genetically predetermined — and that’s one reason why some people are better sprinters and some are better distance runners.
Another interesting tidbit is that a person might have a lot of fast twitch fibers in his lower body but have a lot of slow twitch fibers in his upper body. This could aid a swimmer on his flip turns and start, where he needs to be explosive in his lower body, while allowing him the endurance necessary in his upper body to make it through a long race.
Here’s another way to think of it: In the human body, the muscles responsible for respiration are slow twitch. This is very useful, don’t you think? It would be pretty bad if you got tired breathing, wouldn’t it?
There’s a lot going on behind the scenes at the Olympics. We could all learn a lot this summer if, in all those hours of coverage, NBC found some time to cover the physiology of sports as well as doing human interest stories.
Travis Erickson is director of undergraduate strength and conditioning concentration at the University of Wisconsin- La Crosse. E-mail questions to erickson.trav@uwlax.edu.
