The Difference Between Fast and Slow Twitch Muscle Fibres in Combat Sports

I’m sure you’ve heard at various different times in your training about muscle fibres, and more specifically ‘fast twitch’ and ‘slow twitch’ muscle fibres, and the importance of training specifically to develop each type. But what the hell are the different types of muscle fibre? This article is going to run through the two different types, what they do and how to develop them and most importantly what ones you want to develop to help improve your martial arts.

All the muscles in your body are made up of bundle after bundle of individual muscle fibres which can be categorised into two general types; fast and slow twitch, with fast twitch being further separated into two sub groups which we’ll get into later. The reason they get referred to as fast and slow muscle fibres is due to the speed of the contraction when the muscle activates but they can be known as by different names, such as red or white muscle fibres or, if you’re being more technical, type 1, type 2a and type 2b – which refer to slow, fast and fast respectively. To keep things simple I’m going to refer to them as fast type A, fast type B and slow. If you take the average person, they should have roughly a 40/60 ratio of slow to fast twitch fibres, but with training athletes develop higher percentages of each type depending on what their sport requires.

Let’s start by looking at slow twitch fibres, which take longer to contact, but can hold a contraction for an extended period of time which makes them ideal for endurance events where you’re working for an extended period of time. Physiologically, slow twitch fibres are packed full of myoglobin, which is similar to the haemoglobin found in your blood, and like haemoglobin does in the bloodstream myoglobin is used to transfer oxygen inside the muscle tissue that is used to provide energy for the muscle to contract, which plays a role in their endurance capability and makes them suitable for aerobic exercise (exercise done at a level where your cardiovascular system can provide oxygen to the working muscles). They are also more adapted to burn fat as their fuel source, as opposed to fast twitch which burn primarily glucose. Because they are better for endurance exercise slow twitch fibres are typically found in endurance athlete – a marathon runner can have up to 90% slow twitch muscle fibres, which let them keep run unit all day.

Fast type A fibres contract much faster and are used to generate powerful movements but for a shorter period of time. They have less myoglobin and rely on glucose, which is simple, easily broken down sugar that can be very quickly turned into energy and is stored in the muscles to complete a movement. The fast twitch fibres can generate a lot of power very quickly but fatigue after a short time because of this limited amount of available fuel, and don’t rely on a readily available source of oxygen to work, making them anaerobic.

Finally fast twitch type B fibres are the fast contracting and fasting fatiguing muscle fibres. Their contractions are typically less than a second, and they only fire when absolute maximum contraction is needed. They are also the final muscle fibres to be used, so if you’re doing a maximal effort movement – for example a one rep max of your squat – you’d start off using slow twitch fibres, then fast type A would kick in to provide more power and final fast type B would fire to provide maximal strength to the movement.

So what does this mean for a fighter? Looking at striking martial arts such as Muay Thai or karate you can develop an edge over your opponents by becoming as strong as possible at your weight, and by being able to move from a static position to strike as fast and as powerfully as possible. You also need stamina to continue throwing these powerful strikes over and over again for several rounds. To a lesser extent you also need to be able to keep moving throughout the rounds in order to cut the ring and duck and weave, but it’s widely agreed that boxing is 70-80% anaerobic and 20-30% aerobic, so the vast majority of the energy you use is going to be in those explosive punches and kicks.

There are two main ways to develop fast twitch fibres; maximum effort, and fatigue.

As we said earlier, fast twitch fibres are the most powerful type, they’re used when you need to generate maximum strength. When you try to lift a very heavy weight your muscle fibres begin to fire, starting with the slow twitch fibres, then the fast type A kick in and finally fast type B provide that final push. Often people believe that you need to move fast to generate fast twitch fibres, but this is a misconception. Whilst sprinting is a great fast twitch exercise, and is brilliant for fight conditioning, you can get just as good fast twitch fibres from static isometric exercises. So I’d recommend a combination of all these elements, but my favourite is weight lifting, as it will help improve your strength as well as developing fast twitch fibres. We’ve written previously about the importance of weight training for martial arts, so check out our article Should you be weight training if you do martial arts? and our Basic Fighter Strength Training Program for our recommended plans.

The other method to help develop fast twitch fibres is fatigue – as your muscles get tired they fire more and more fibres to maintain a workload as long as you’re working at a high intensity. I’m not talking about running 10 miles at a solid pace, that’s working your slow twitch endurance system. I’m referring to short bursts of activity repeated at maximum intensity even as you tire. The most relevant to martial arts would be pad or heavy bag work – really pushing yourself with multiple rounds of maximal effort striking even as you fatigue – and cardio work such as skipping and sprinting, again it’s only effective if you put in 100% effort during the round, and then have a short period to recover.

So, if you want to maximise your fast twitch fibres you should start by getting some pre workout sugars to fuel those fast twitch fibres – a glass of fruit juice or a protein shake with dextrose powder. Then you need to lift heavy weights (80%+ of your one rep max) and seriously push yourself during your pad work sessions and your cardio. Remember, if the pads arent bending, you’re just pretending.

As always, Fight Quality advises you do your own research into any new training techniques, and consult a professional before undertaking any new exercise.