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Outsmart your muscles by training your fast and slow twitch muscle fibres.

Forget endless hours sweating out in the gym. If honing your shape and toning up are your aims, it could come down to the specific muscle fibres you are using, not the time logged lifting weights. 

So what are fast twitch and slow twitch muscle fibres?

We’re all made up of two general types of skeletal muscle fibres – fast twitch and slow twitch.

Fast twitch muscles can fatigue quickly but are useful in powerful short bursts of movement and slow twitch muscles enable long-endurance movement like marathon running.

During high-paced cardiovascular exercise, like swimming or running, slow twitch fibres are the first to contract and when they become tired, fast twitch fibres take over.

Naturally, we all have predominantly one type of fibre more than the other, but we can train each type to help us perform better – but even though genetic makeup does account for slow and fast-twitch muscle fibre ratios, we can all train both muscle fibre types to become more efficient.

It’s important to note that there is no conclusive evidence that muscle fibres can transform from slow to fast twitch or vice versa… whether you’re fast or slow twitch dominant is largely genetic, so it’s unlikely that you’ll convert your muscle fibres.

Studies show that training both fibre types is still incredibly beneficial as any improvement you’ll see in your muscle condition and overall fitness is generally holistic. For example, you may improve at a type of movement through repetition and dedication, which makes for a positive, sustainable lifestyle change.

What are the benefits of working fast twitch vs slow twitch muscles?

Working both types of fibres has benefits, regardless of which type of muscle fibre you find is more naturally dominant/preferred for you. 

There are great health advantages to exercising your muscles to the point of temporary fatigue and making sure that your fast twitch fibres have been activated. This will help you increase your muscle mass and improve your strength.

Fast twitch muscle fibres can be trained with:

- Intense, short duration exercise and weight training with rapid, low numbers of reps and heavier weights, which will train you in consistently producing a fast and forceful effort

- Longer rest periods between exercises, which will allow energy replenishment

- Fast, intense workloads like deadlifts, bench presses, sprints or sled drags, which will push the muscles and force continuous improvement to take place.

Slow twitch muscle fibres can be trained with:

- Sustained isometric contractions (like planks), which will challenge the fibres to improve their aerobic capacity

- Resistance training with 15 or more reps at a lighter weight, which will help you keep your movements smooth and sustained

- Low resistance circuit training and continued movement without a rest break, which will improve capacity

- Incrementally increasing your distance (for running, cycling or walking) whilst maintaining a moderate intensity, which will build endurance and aid your body’s ability to use oxygen to fuel movement.

Whether you’re trying to train your fast or slow twitch muscle fibres – dedication is paramount.

“One of the biggest rookie mistakes I see over and over again is that people are turned off following their first class and therefore don’t come back again. That’s because it’s intense and their muscles are sore afterwards,” says Kylie Archer from Melbourne’s K-Kore Fitness Studio.

“It’s important to leave it a few days and then come back again. Once your muscles adapt to the change the soreness during and after class will decrease significantly. Prepare to go slow. Doing this forces the body to use as many muscle fibres as possible. Effective tempo will activate those very important slow-twitch muscle fibres which are your endurance, toning and fat-burning muscle fibres. Ultimately in any form of high intensity resistance training, slow is better as greater muscle activation leads to less wear and tear on the joints.”