When it comes to fat loss, ever wondered who hits harder, BIG or FAST?
Toni did when he asked…
“I have a question regarding weight loss and punching power. Let’s imagine we have 2 genetically identical fighters…
Muay thai fighter 1 weighs 90 kg but is physically less muscular and fat.
Muay Thai fighter 2 weighs 78kg but is physically fitter, has more muscle mass through maximum strength, explosive and speed strength training.
Which of the two hits harder? The heavier or the fitter?”
I love this, it’s right up my street! I’m going to use some simple physics to reveal exactly who wins this punching contest and why!
by Don Heatrick
@donheatrick
Big Or Fast, Who Punches Hardest?
In this episode we’ll prove if being heavier, or being faster results in the hardest punch, so you can decide if losing body fat will reduce your KO ability, and how to best train to deliver the most destructive strikes possible.
Taking Toni’s question, I’m going to standardise it to make it a fair test, and we can see who would REALLY hit harder…
We’ll assume both fighters have the same level of Muay Thai technique and relative strength for their muscle mass. We’ll then make this a little more extreme than Toni’s proposed example, and say that both fighters also have the same amount of muscle mass…
- Fighter 1 weighs 90kg, has 22% body fat, and has 70.2kg of lean muscle mass
- Fighter 2 weighs 78kg, has 10% body fat, and also has 70.2kg of lean muscle mass

So literally the only difference between these two fighters is 12kg of body fat. Fighter 1 is just over 15% heavier, but has no strength advantage.
Because both fighters have the same amount of muscle mass and strength, their force production is the same. But Fighter 2 has less mass, and being 12kg lighter will accelerate over 15% faster according to Newton’s 2nd law of motion (F = m x a).
Just like you’ll lift yourself quicker on a chin up bar if you don’t have extra weight added to you.

Accelerating faster means that Fighter 2 will reach a higher striking velocity by the time the punch lands given the same range or distance.
So now we really are comparing who hits harder, the heavier fighter or the faster fighter.
We’re comparing weight and speed, which is mass and velocity in scientific terms.
And using those two variables we can check out which combination generates the most destructive strike. And the best measure for this is kinetic energy.
Practical tests using arrows penetrating targets show that the greater the kinetic energy, the deeper the arrow sinks into the target. And the same is true of our punch too.

When we look at the kinetic energy of a strike, both mass and velocity matter. But, velocity is squared in the equation, making it twice as important.
Very simply…
If you double the MASS, you double the kinetic energy.
But if you double the VELOCITY, you quadruple the kinetic energy!
In our example, despite being lighter and by virtue of being faster, Fighter 2 will be capable of hitting harder than the heavier Fighter 1 because they have a higher strength to weight ratio.


So either, or both reducing body fat while maintaining muscle mass, or training to increase neuromuscular strength without gaining muscle mass, will both increase your force production and your potential to explode faster, creating more kinetic energy and more KO power.
And if you want help understanding how to build neuromuscular strength, or reducing body fat while maintaining muscle mass and strength, I’ve put links to further resources for you on the show notes page for this episode too.
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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.
Follow Don Heatrick on Instagram: https://www.instagram.com/donheatrick/
Well yes and no to be honest. Are you saying a heavier fighter will not hit harder than a lighter one? Would Nigel Benn have won in a toe to toe with Mike Tyson? Extra weight ALWAYS wins with skilled conditioned fighters
Thanks for sharing your thoughts Cliff, and I 100% agree!! There are weight categories for a reason!
When fighters are both bigger AND stronger, they’ll hit harder. The purpose of this worked example was for the same fighter both before and after fat loss, with no other variables changed (strength, power, speed, technique are all deemed identical). It’s easy to get lost in detail when you start changing other factors too, and that doesn’t help answer the question, “will losing fat (only) will reduce how hard I can hit?”
Thanks for raising this point of confusion, I certainly need to do a follow up video to clarify all this!
Another informative article Don, well done.
Thanks Luke! :)
I’ve studied physics and I was pleasantly surprised to find that you understand physics so well. My compliments: you are right on the money, so to speak.
Thank you Orlando, I appreciate you feedback immensely. These kind of topics tend to polarise folks, and I know this video will create an adverse reaction as much as a positive one. But I thought it was both and interesting question to be asked, and a valuable consideration to share. :)
if it s Newton’s 2nd law of motion (F = m x a) why on earth did you put the face of Einstein?
Fair point… Just being lazy as I already had an image I’d made of Einstein wearing a Mongkon that I liked! Meant it as a physics reference.