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The Summary of Things (Fast Twitch to Slow Twitch, Part II)

As a preliminary matter, distinctions between weightlifting and triathlon are vast when it comes to the types of training and “muscles” used.

[If you don’t care about this part, skip down to the next post]

Also, please note that this post is meant to be a summary and a simple primer. I am not digging into deep anatomy and physiology. This post is generally speaking about FT and ST muscles).

Generally, we classify weightlifting as “fast twitch” and triathlon/endurance work as “slow twitch.”

I say generally, because there’s a place for both twitches in triathlon (short course v. long course)—which is not the case in weightlifting, really.


Olympic Weightlifting was an explosive-type movement and series of training, hence the term fast twitch. 

Fast twitch fibers are amazing and explosive—but those powerful muscles fatigue super fast… which means, you can’t go at fast-twitch intensity forever. Fast twitch muscles are heftier, speedier to contract, and hence, they blow out quicker than slow-twitch.

From a physiology stand point: think about how the weightlifters are thicker people—the muscles are thicker (fast twitch); long-distance runners have leaner, longer muscles (slow twitch).

Fast twitch fatigue is part of the reason when you are lifting heavy, you must take rests in between sets.  Those muscles require rest in between, or they simply can’t keep going.

Marathons, ultra-running, and longer course triathlon pulls in mostly slow-twitch muscle fibers. “Type I, slow-twitch muscle fibers, are also known as aerobic muscle fibers due to their ability to create energy from oxygen, allowing them to produce force over an extended period of time.” (Source).

Of course, as you can see from the chart, triathlon also has a place for explosive movements – especially in short-course racing such as sprints and ITU.  But that’s part of the reason we can’t go at our own sprint distance race pace… for the span of an IRONMAN.

I learned the amazing nature of fast-twitch explosive movement in my years of weightlifting… but weightlifting did me absolutely zero favors for (slow twitch) endurance-type training.

Where does fast-twitch cross over very well into triathlon?

This was the main question someone had for me. I can say that it crosses over in shorter distance races. Climbing hills on a bike. When you need to sprint ahead of someone on the swim, bike or run.  Heading out hard on a swim. In a 5k. On strength training days. When you need to jump.  You get it. Fast-twitch is a good thing to have in your arsenal.

Additionally, one of the reasons that I have been able to haul my heavy body across the 112-mile bike courses of Couer d’Alene, Lake Placid and Louisville?  Yes, I had trained for those, but I also had very  strong legs at one point in my life.  Fast-twitch translates to strength.

When I climb short hills or push hard on the bike in training, my body sings a familiar song – it’s like, “Oh I know this stuff.” And when I may go slower than my 120-pound counterparts due to something called gravity—I am strong, and it takes strong legs to haul 190+ pounds up a mountain—or anywhere on a bike for that matter.

Okay, so back to two (of the many) lessons I have learned from weightlifting that cross over into triathlon.

Back to Part I
Forward to Part III

One Comment

  • Andrea Searby

    October 18, 2017 at 5:58 pm

    First off.. again, thank you SO MUCH for writing out this series!!

    It’s really interesting to see you say your weightlifting background didn’t really (physically, at least) prepare you for the necessary components of endurance racing.

    As a not naturally fast twitch, mediocre weightlifter who found weightlifting via CrossFit (10 years ago, when it was a very different phenomenon), I think I got lured into the idea of selective crossover training, with more explosive training as the priority. As in, anyone can slog through submaximal endurance work *scoff* but it’s a lot more impressive to explosively lift weight off the ground. … maybe it is, in isolation, because there is no technical comparison. But I like reading the respect you give the long slow endurance work.. I’m learning this the hard way myself!


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