Fast-Twitch and Slow-Twitch - What does it all mean?

Fast twitch and Slow Twitch Muscles

If you have hung around the gym enough these terms have probably popped up. But what exactly do they mean? Are they just ‘wank words’ or is there something to  them?

Well, there are different types of muscles in the body which are classified based on how they produce energy. These are generally described as slow-twitch or fast-twitch.[i]

Slow-Twitch (Type I) Muscle Fibres

• These can produce their own source of energy and therefore can sustain a force for an extended period of time.

• However, they are unable to generate a lot of force.

• They are activated first due to their low activation threshold.[ii]

Fast-Twitch (Type II) Muscle Fibres

• There are two sub-types, IIa and IIb. The IIa muscle can also act lik a slow-twitch muscle fibre depending on what activity we are dong.

• Fast-twitch muscles are recruited if the slow-twitch ones can’t produce enough force.

• Generate more force but get tired quicker.

• Generate peak force quicker.

• Responsible for the definition and size of a muscle.[iii]

Conclusion

In short, slow-twitch muscle fibres are about long-lasting endurance, while fast-twitch muscle fibres are good for sudden bursts of energy.[iv]

Next week we will at what we use each of these muscle fibres types for.

[i] https://www.acefitness.org/education-and-resources/professional/expert-articles/5714/muscle-fiber-types-fast-twitch-vs-slow-twitch/

[ii] https://www.acefitness.org/education-and-resources/professional/expert-articles/5714/muscle-fiber-types-fast-twitch-vs-slow-twitch/

[iii] https://www.acefitness.org/education-and-resources/professional/expert-articles/5714/muscle-fiber-types-fast-twitch-vs-slow-twitch/

[iv] https://www.healthline.com/health/slow-twitch-muscle-fibers#slow-twitch-activities