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There’s a lot of confusion and debate about how muscle fiber types relate to muscle growth.

Some people say only fast-twitch muscle tissue can get big and strong and some of us naturally have more or less of it and can’t change that regardless of what we do in the gym.

Others say both fast- and slow-twitch muscle can grow bigger and stronger and the makeup of our muscles is malleable, but we shouldn’t take any special measures in our training to try to emphasize one muscle type over the other.  

And others still say “muscle-specific hypertrophy” training—using different rep ranges with different muscle groups based on their dominant fiber type—is the optimal approach to training, and especially as an intermediate or advanced weightlifter.

Who’s right? 

Well, I wasn’t even sure myself, that’s why I invited Dr. Andy Galpin on the show to explain.

In case you’re not familiar with Andy, he has a PhD in Human Bioenergetics, teaches various university-level courses on sports nutrition and exercise physiology, and heads a lab that runs studies on muscle fiber type and muscular adaptations to exercise on a cellular level. 

His lab is also conducting an intermittent fasting study to learn more about the implications of fasted training on muscle growth, which I’m helping fund through my sports nutrition company Legion Athletics.

Time Stamps:

6:38 – What are the different types of muscle fibers?

13:49 – Is muscle fiber type the main reason why people gain muscle faster than others?

23:14 – Why do you think the olympic lifters had more fast twitch muscles?

24:37 – Can some people transform from type 1 to type 2 faster than other people?

26:16 – Is this information useful for normal lifters or experts? Should training be optimized or altered according to muscle fibers types?

28:58 – How do you emphasize building type 1 and type 2 muscles?

40:12 – How should people perceive muscle groups and how does that affect your exercise routine?

46:20 – Can you lose your fast twitch muscles by focusing on slow twitch?

55:10 – Where can people find you and your work? 

Mentioned on The Show: 

Books by Mike Matthews

Bigger Leaner Stronger

Find Dr. Andy Galpin Online:



What did you think of this episode? Have anything else to share? Let me know in the comments below!