Muay Thai, Muscle Growth & Reps

There’s certainly a lot of opinion when it comes to muscle mass and Muay Thai. In this brief post I hope to clear up some of the confusion and help you steer your training in the direction you want, whether that’s putting on muscle or keeping it off!

Even using identical exercises, resistance training produces drastically different results depending on the weight used, the number of sets and reps and the given rest intervals. Before I can explain further, you need a basic understanding of the structure of a muscle fibre. Every muscle fibre consists of many parallel, contractile strands called myofibrils. Surrounding these myofibrils is a volume of non-contractile protein and semi fluid substance called sarcoplasm.

muscle fibre

Two Types of Muscle Growth

A muscle can gain size (hypertrophy) in two different ways, and your training can target one or the other or a combination of the two. Bodybuilders obviously target both types of growth, they just want to be a big as possible. But Thai boxers must be more specific or  you’ll hinder performance with non-functional bulk that’ll slow you down without increasing strength.

Sarcoplasmic hypertrophy results from an increase in the amount of sarcoplasm surrounding the myfibrils. This supports greater strength endurance but doesn’t make you stronger. We don’t want this kind of growth, it will slow you down and mess up your power to weight ratio.

Myofibrillar hypertrophy results in an increase in the number of contractile myofibrillar strands, making the muscle denser and able to contract with more force. If you’re going to put on muscle mass, this is the kind that we want.

How Many Reps?

The exact biomechanical mechanism for muscle growth from resistance training is not yet fully understood, but that’s just academic, it doesn’t really matter to us. We only need to understand the practical application and adjust our training programmes accordingly. So here’s the low down, where the rubber meets the road.

If you want strength without an increase in muscle mass, using a load you can lift only between 1 and 5 times will increase neuromuscular efficiency – make you better at recruiting the muscle fibres you’ve got rather than make more muscle. You get stronger without getting heavier, increasing your strength-to-weight ratio so you can move faster and be more powerful. Combine this rep range and intensity with rest intervals of 3 – 5 minutes between sets to get the best ‘spark’ from your neuromuscular system and the best strength gains.

If you want to gain some muscle with a proportional increase in strength, use a load you can lift between 6 and 8 times to benefit from myofibrillar hypertrophy. You’ll get heavier, but you’ll be stronger too and shouldn’t slow down. Use rest intervals of less than 2-minutes between sets to boost the hypertrophy effect. With more muscle, you’ll also have the potential to get even stronger if you follow with a strength training phase to improve neuromuscular efficiency.

Using a load that you can lift between 9 to 15 times or more will result in sarcoplasmic hypertophy, an increase in muscle bulk without an increase in strength – you’ll get slower. Again, resting 2-minutes or less between sets will enhance muscle hypertrophy.

Rep Range Continuum

It’s a Sliding Scale

Now these rep ranges are not discrete, with up to 5-reps developing purely strength and 6-reps purely muscle growth. In reality there’s a gradual transition in the strength/hypertrophy effects we’ve discussed all the way along the repetition continuum. And individuals all respond to training differently. For example, depending on your genetics, 5-reps could make you grow muscle. If that’s not desirable, drop the rep range and increase the load to target strength alone. The rep ranges I’ve outlined are true for the majority, but be prepared to adjust based on how you individually respond to the training stimulus.

If You Do Want More Muscle Mass

When it comes to individualisation, I’ve noticed that in general leaner, less muscled fighters tend to grow better using the 6 – 8 rep range, and fighters more predisposed to putting on both muscle and fat gain more muscle toward the 10 – 15 rep range. Use a higher training volume too, 4 – 8 sets per exercise tend to do the trick if you want more size.

Well that wraps up my brief review of resistance training rep ranges, the physiological effect with respect to muscle gain and how it affects Muay Thai performance. Be prepared to adjust your training to suit you as an individual depending on how your body responds to the stimulus. I hope this insight helps you tweak your training and bodyweight for the best advantage in your weight category — whether that’s keeping your weight down while improving strength, or gaining a bit more functional weight and strength. But don’t train for show, train for go!

Don Heatrick

Founder of Heatrick Strength and Conditioning

Don Heatrick is a family man from the UK, former mechanical design engineer, European Muay Thai silver medallist, former pro Thai boxer (ranked 4th in UK while aged 40-years), a Muay Thai coach, podcast host, and the go-to expert on Muay Thai performance training with over 25 years of coaching experience.

Don helps ambitious fighters and coaches take their game to the next level by bridging the gap between Strength & Conditioning, Performance Science, and Muay Thai.

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