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


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.


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


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.


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!

By |2018-06-20T20:26:07+00:00September 7th, 2014|Hypertrophy, Periodisation, Power, Programme Design, Strength, Written Post|22 Comments


  1. sherbs September 7, 2014 at 10:08 pm - Reply

    These articles are really useful. Thanks Don!

  2. James McKie October 19, 2014 at 2:41 pm - Reply

    What does this mean for anatomical adaptation, where reps are generally in the 10-15 range?

    • DonHeatrick October 20, 2014 at 12:09 pm - Reply

      Great question James.
      During an anatomical adaptation (AA) phase the priority is loading tendons and ligaments rather than muscle. Therefore, although the rep ranges used in an AA phase may well be the same as those used for hypertrophy, the load isn’t. Typically between 40% to 70% of 1-rep maximum load is used, phased over 4-weeks or so.

      I’m finishing up a series of videos specifically explaining all about the AA phase, and also an AA phase programme for release very soon.

      Good, thoughtful questions as always James, thanks for your input. :)

  3. Alex P December 29, 2014 at 6:36 pm - Reply

    How many days a week you recommend lifting for muscle growth and how would you split the sessions? Is it good to work mainly on compound movements?

    • DonHeatrick December 30, 2014 at 10:43 am - Reply

      Hi Alex,
      As always, it’s a balancing act around your Muay Thai skill training, but if increasing muscle mass is a priority I’d recommend 3 or 4 sessions (days) per week.

      If you’re using three sessions per week, hit the whole body each time with compound lifts (see this article for more detail), and don’t train consecutive days.

      If you’re training four sessions per week, you’ll need to train on consecutive days – and you’ll need to use a split system. For example, Monday and Wednesday train double-leg or single-leg knee-dominant lifts along with horizontal and vertical pulls; Tuesday and Friday train double or single-leg hip-dominant lifts along with horizontal and vertical presses. Be careful to monitor how you are recovering from this 4-day regime and how it affects your Muay Thai training and adjust accordingly. Consider reducing the lower-body lifting to knee-dominant exercises on Monday and hip-dominant lifts on Wednesday only, giving the legs a rest on Tuesdays and Thursdays, substituting additional core work instead.

  4. Matt Howard January 9, 2015 at 8:00 pm - Reply

    Great info. Any truth to the speed of the lift in regards to strength vs power and not necessarily gaining muscle mass?

  5. eric April 2, 2015 at 4:42 am - Reply

    Thank you for this I’ll be trying this out

  6. jordan April 2, 2015 at 3:06 pm - Reply

    U have an advise for ppl like me who only train with free weights??? Dual training…

    • DonHeatrick April 2, 2015 at 3:57 pm - Reply

      Hi Jordan, I’m not sure what you’re asking? Do you mean someone who isn’t also training Muay Thai or other sports, who is just gym training for increased muscle mass?

      • Norman November 4, 2015 at 12:44 pm - Reply

        Hi Don, I would like to ask 1 more time if how many sets of the said reps between 1-5 to have “Increasing Neuro muscular Efficiency”? sorry this is a bit late to ask…..

        thank you for the article and best regards :)

  7. Norman October 16, 2015 at 12:13 pm - Reply

    Hi don, Norman here. Im training at a local gym here in the philippines in muaythai… i traing 4-5 days a week. about the “Myofibrillar Hypertrophy” part i want to gain muscle but doesnt affect my strength and power do you have specific forms on these exercises that i can check and when i should do these exercises by any chance…. great info but i just want to know alittle more about the indepth details of this intricate exercise.. thank u :)

  8. Mohammad Hadid November 2, 2015 at 5:14 am - Reply

    Hi Don, it’s Mohammad from Lebanon. I wanna thanks u for these useful articles, Muay Thai, Muscle Growth& Reps it’s my first article i read it by chance but i got all what i need and wondering in simple and easy way, and what is the things that our coaches couldn’t explain for us, thank you don again. Best Regards

    • Don Heatrick November 4, 2015 at 7:41 am - Reply

      Hi Mohammad, thanks for taking the time get in contact. I’m glad to help. :)

  9. Victor November 18, 2015 at 2:34 pm - Reply

    wow it’s a great article there. Usually i lift about 15-20 reps on my muay thai exercise, so if I want get Myofibrillar hypertrophy effect, i just do 6-8 reps?but what about the weight?should i lift the maximum weight or not?thx.

    • Don Heatrick November 18, 2015 at 6:06 pm - Reply

      Yes that’s right Victor, typically 6-8 reps will do the trick there. And use a load that you can lift up to a maximum of 6-8 times for your programmed high weeks (Max load).

      • Victor November 19, 2015 at 3:50 am - Reply

        great to know this article…thanks man !

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