Rob Bridges explains

Fast Twitch, Slow Twitch…..

What does Fast Twitch/Slow Twitch mean? And how does this affect me and my training?


There are 2 types of muscle fibres, Fast Twitch (FT) and Slow Twitch (ST) and each of us have different percentages, eg a Olympic sprinter might have up to 80% FT fibres and a Olympic marathon runner might have 80% ST fibres. These muscles fibres are your genetic make-up and generally the percentages of each won’t change over time.

Physiological Make Up

When training as an athlete there are a few things that you need to understand about your own physiological make up. A training program for one person my not necessarily work for another. This can be down to a number of things: age, sex and history in the sport are the fairly common ones, but predominance of muscle fibre type also plays a big role and something that isn’t always understood or utilised in training programs.

There are 2 types of muscle fibres, Fast Twitch (FT) and Slow Twitch (ST) and each of us have different percentages, eg a Olympic sprinter might have up to 80% FT fibres and a Olympic marathon runner might have 80% ST fibres. These muscles fibres are your genetic make-up and generally the percentages of each won’t change over time.

Triathletes also vary in percentages of muscle fibre type, now you probably wouldn’t get someone like Usain Bolt doing an Ironman, but many who have higher than average FT fibres can still do well in triathlon.

At TTT we can do some quite simple tests to understand what training would be best for you.

Characteristics of FT and ST athletes

Here we have our very own TTT coaches pictured with the worlds best athletes. Demonstrating wherever you are on the scale of FT/ST, you can still perform to your best by knowing what training suits you and your physiological make up.

FT ST coaches image

To Conclude

Being Fast Twitch or Slow Twitch does not mean being fast or slow. It is a genetic make up of your muscle fibres and something that you can work with to your advantage.

Talk to your coach about how best to do this.

Rob Bridges

Senior Triathlon Coach.