Different Muscle Fibre Types Determine Whether You Are A Sprint or Endurance Athlete

Question from Aaron Yeo:

Nice article about Endurance vs Sprint Athletes. So what is the difference between type 2a and 2x muscle fibres?


My Reply:

We have 3 types of muscle fibres in our body, mainly type 1, type 2a, and type 2x. Like I said in my previous blog post, type 1 is slow twitched muscle fibres which are for endurance athletes whereas type 2 muscle fibres are fast twitch which are for sprint athletes. Here are more details of each of the muscle fibres:


Type 1:

–          Low in force production, suitable for long duration and low intensity exercises

–          Fatigue resistant

–          Suitable for endurance races like a 1500m swim or marathon


Type 2a:

–          Moderate in force production

–          Slightly fatigue resistant due to having similar characteristics as type 1 muscle fibres

–          Suitable for high intensity and short duration races like a 200m/400m swim or 800m run


Type 2x:

–          High in force production

–          Fatigues easily

–          Suitable for very high intensity and short duration races like a 50m swim sprint, 100m run or power lifting which require a lot of explosive force


World Class Swimmers With Different Muscle Fibre Types: 

Type 1: 


Sun Yang, the world record holder for 1500m Freestyle, has predominantly type 1 muscle fibres.


Oussama Mellouli is the 2008 and 2012 Olympic Champion for the 1500m Freestyle and 10km Open water race. He definitely has predominantly type 1 muscle fibres.

Type 2a:  


Phelps on the other hand dominates practically everything from 100m – 400m races, he has predominantly type 2a muscles fibres, which explains why he can do endurance races and sprint races at the same time.


Park Tae Hwan is similar to Phelps, which explains his endurance in the 200m/400m races and also his speed in the 100m races.

Type 2x: 


Sprinter Cesar Cielo Filho is the world champion in the 50m Freestyle and Butterfly races, he definitely has predominantly type 2x muscle fibres.


So which type of athlete are you? Do leave a comment at the comment section below 🙂


Got a question as well? 

Feel free to email me at hello@pangshengjun.com or simply leave a comment below and I will be happy to answer them for you.


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14 Replies to “Different Muscle Fibre Types Determine Whether You Are A Sprint or Endurance Athlete”

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  9. Just came across this post and really enjoyed it. What I am wondering is, if Sun Yang and Mellouli have predominantly Type 1 “slow twitch” muscle fibers, how is it that Sun Yang can also win an Olympic gold medal in the 200m freestyle, plus a bronze medal in the 100m freestyle at the National Games of China, and Mellouli can medal at the World Championships in the 200m freestyle+IM, as well as win gold in the 50m and 100m freestyle+butterfly at the Pan Arab Games (against multiple Olympic competitors in those events)? How is this kind of versatility possible, and what does it say about their muscular structures?

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