Fast Twitch or Slow Twitch: Which Are You?
- There are two main types of muscle fibres – red fibres (also called fast twitch) and white fibres (also known as slow twitch).
- The slow twitch cells are helpful for endurance sports.
- The fast twitch cells tend to fatigue much more easily, but they are excellent for short bursts of power which are necessary for sports like sprinting and powerlifting.
- Some people are born with a far greater amount of one type. It stands to reason, therefore, that those people would have an advantage in certain types of sports as well.
When we see athletes who are top in their field, it’s common to attribute their success to an innate ability. Comments such as, “He’s got hockey in his blood” or “She’s got running in her DNA” may be made in jest – but is there any truth to the notion that athletic ability could be determined by genetics? Could a DNA test predict whether you are likely to be a good weightlifter or long-distance runner?
The fact is, that we are a long way off from a definitive test because the genetic factors that determine athletic ability are quite complex. There is one physical trait, however, that seems to be more important than most others and that is our ratio of fast twitch to slow twitch muscle fibres.
WHAT ARE MUSCLE FIBRES?
Muscle fibres are simply muscle cells – we call them fibres because they are long and thin – like threads. There are two main types of muscle fibres – red fibres (also called fast twitch) and white fibres (also known as slow twitch).
The slow twitch cells are helpful for endurance sports. Someone who trains in marathon running or cycling will cause these fibres to grow and the muscles will develop with a long and lean appearance.
The fast twitch cells tend to fatigue much more easily, but they are excellent for short bursts of power which are necessary for sports like sprinting and powerlifting. Train in these types of activities and your fast twitch fibres will grow. These muscle fibres grow larger and bulkier than slow twitch.
Finally, there is a third subset of muscle fibres – these are fast twitch fibres that can be trained to act like slow twitch. These fibres will act either as fast twitch or slow twitch depending on what activities you train in.
WHAT TYPE ARE YOU?
Most people are born with relatively equal amounts of fast twitch and slow twitch muscle fibres, but this is not universally true.[i] Some people are born with a far greater amount of one type. It stands to reason, therefore, that those people would have an advantage in certain types of sports as well.
Those with ancestry from West Africa are more likely to have an abundance of fast twitch muscle fibres, while those of East African descent are more likely to possess more slow twitch muscle fibres. These differences are most obviously displayed in the Olympic games where sprints are dominated by athletes with West African genes; and distance races see most of their medalists come from East Africa.[ii]
WHAT IT ALL MEANS
At the very elite levels of sports, the role of DNA is probably larger than most of us care to admit, but it still takes plenty of hard work and training to get there. But for those of us who will never take our athletic pursuits past a recreation level – and that’s most of us – ability is mostly determined by how we train.
For those, however, who have an extreme dominance of either fast twitch or slow twitch muscle fibres, genetic testing will give you some insight into the type of sport in which you are most likely to excel.
[i] https://geneticliteracyproject.org/2015/01/08/can-we-yet-use-genetics-to-determine-which-sports-are-best-for-our-kids/
[ii] https://www.forbes.com/sites/jonentine/2012/08/12/the-dna-olympics-jamaicans-win-sprinting-genetic-lottery-and-why-we-should-all-care/#32970eb82a2e