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Physics of Martial Arts?

by Gaijinja
Tags: martial arts, physics
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Mar26-07, 06:14 PM
P: 6
Does anybody know a good source for information regarding the physics of Martial Arts? I'm a long time Martial Artist and an amateur physicist, and I think a better understanding of the physics behind a lot of my techniques will allow me to refine and develop better techniques.

And yes, I do understand basic concepts such as Newton's laws of motion, momentum, impulse, etc.

Thanks in advance!
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Mar26-07, 06:33 PM
berkeman's Avatar
P: 41,303
I tried a slightly less specialized term in my google search, and got a number of good-looking hits. Here is the hit list for a google search of "physics of boxing":
Mar26-07, 06:36 PM
Sci Advisor
ShawnD's Avatar
P: 986
Your passion for learning is good, but it's really better to just ask somebody who is a pro at martial arts. Most of that stuff has good mathematical reasoning, but much of it is counter-intuitive; that means you won't figure it out on your own but it makes sense after you've been told.

An example would be why jump kicks in video games don't work in real life. If you jump to kick something and fully extend your leg before it reaches the target, the only energy you can apply is the momentum associated with your weight. If you only half-extend your leg until your foot reaches your target, then fully extend, you are able to apply the momentum of your body as well as the muscle power in your legs.
The only reason I know this works is because I've seen TV shows where cops try to kick down doors, and I've kicked my fair share of vending machines. I never would have figured this out based on physics alone; the observation comes before the theory.

Good luck with your training.

Doc Al
Mar26-07, 07:02 PM
Doc Al's Avatar
P: 41,565
Physics of Martial Arts?

Quote Quote by Gaijinja View Post
Does anybody know a good source for information regarding the physics of Martial Arts? I'm a long time Martial Artist and an amateur physicist, and I think a better understanding of the physics behind a lot of my techniques will allow me to refine and develop better techniques.
I've read several "physics of martial arts" articles over the years, most of which I've found comically oversimplified. There are too many subtleties that can only be learned with practice. Nonetheless, I like much of what Martina Sprague has written in her several books on the "science" of fighting--check her out; she's a serious martial artist--that counts for something. (Note: The physics in her books is high level "conceptual" stuff, but useful nonetheless--especially if you teach others. And I don't necessarily endorse the particular techniques she discusses--that's a personal choice.)

FYI: I am also a lifelong martial artist.
Ki Man
Mar26-07, 07:24 PM
P: 555
It may not seem like the technical answer yo're looking for but i find watching bruce lee fights useful for increasing the right form of punches and kicking. He also wrote some books on martial arts technique so you should check some of those out.

I agree with Shawn though, the best way i've found for improving my techniques is with advice of a senior
Mar26-07, 07:33 PM
P: 200
From a google search I did just now I got this page, which doesn't seem like anything special, but which does mention a term called "kinetic linking" that seems important. I was thinking about the relationship between physics and martial arts a while back (I'm a martial artist) and one thing I realized is that the collision of your fist and their body is much more complicated than simply transferring the momentum of your fist to their body. If you tense up your muscles at the moment of impact of your punch, if you keep your elbow anchored (i.e. don't stick it out or up), if your legs are in a strong position when you make the hit, and whatever else it takes to make your body stronger in the direction of the punch, then your punch is more effective.

(I was going to say "your punch has more power" but I'm too unsure of the physics to know if that's right. It may not even be relevant. If you were to tell your opponent to wait a minute, then run to your local speaker store and buy a sound system, connect it to some power supply in whatever alley you happened to be in, then played high volume rock music, it's possible a lot of power would be transferred into his body, but it wouldn't be effective. The moral of the story is that for martial arts physics you'd need specific, appropriate terminology.)

Anyway, my guess is that the above statement I made about making your body strong at the moment of the punch is correct because of the following: When you punch, the first force exerted is due to the normal force acting against your fist. Instantly, your fist begins to recoil, and that recoil energy is transferred backwards until it either gets absorbed by some part of your body (say, if your back knee turned outwards, causing your body to rotate) or it becomes reflected somewhere, perhaps off of the floor due to the friction between it and your feet, perhaps just due to the way waves tend to reflect when they get to a region of a different index of refraction. So, in summary, I think the main part of the effectiveness of the punch is due to controlling the propagation of waves within your body.
Mar26-07, 08:14 PM
P: 6
Wow, all the prompt replies. Thanks everybody.

Hmm, interesting, a lot of physicists seem to also do Martial Arts (or at least, the ones that do are all responding to this).

Thanks for all the input, but I will say I was aware of most of the information presented (not to discourage anybody, though). I guess I'm just looking for some in depth physics explanations for, say, why kinetic linking works. I mean, there are many techniques I know will work better one way than another, but I'm curious to the exact physics behind it.

I dunno. But hey, a discussion on the physics of martial arts is always fun, right!
Mar26-07, 09:04 PM
Sci Advisor
FredGarvin's Avatar
P: 5,095
Kinetic linking. What a load of crap. I guess it doesn't sound cool if you just say that you need to have a stable base.

Honestly, your best bet is to not let your head get too much into it. Practice, practice and practice. Your body will feel it's way to the right techniques. The kinetics of human movement is incredibly complex. The interactions and differing forces created at different times in a single motion make it very difficult to describe techniques in simplistic terms.

Having someone to guide you and to point you in the right direction is great advice.
Ki Man
Mar26-07, 09:45 PM
P: 555
Quote Quote by FredGarvin View Post
Kinetic linking. What a load of crap.

I love training with nunchucks and that kinetic linking bit that was shown on the site made no sense to me. I dont see why the site claims it is so evident in nunchucks even though the principle of inertia applies to everything in THE ENTIRE UNIVERSE, not just chained weapons. Inertia is everywhere, that kinetic linking stuff was just thrown in to fill space. kick someone in the ribs and thats kinetic linking enough for you right there. he makes it sound like those of us who use nunchaku are physics gods (which is flattering, but i doubt the accuracy of) although, using chained weapons does require a good sense of force and motion, this guy is trying to evercomplicate some very simple things
Mar26-07, 10:00 PM
P: 6
The guy also implies that by swinging a nunchaku you can "build up inertia"
Mar26-07, 10:09 PM
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Pythagorean's Avatar
P: 4,292
I used to be in martial arts, and am also a physics major. (Actually going to start training again starting tomorrow, I've gotten very inactive since overloading on physics courses every semester)

I saw a special on TV where they had sensors linked all over these people's bodies so you could see there muscle contractions and (simplified biomechanics, I guess)

I don't know how credible it was, or whether the editors "photo-chopped" the animations from the sensor program, but I remember specifically something that my sensai taught me comparing well with the technical aspects this program showed:

My sensai (more abstractly) taught that the punch should come from the ground. He implied something like it should travel up your foot and into your hips, up your back muscles, out your shoulder, down your arm, and snap out the end of your fist. (more generally though, you put your whole body into the punch, you don't just swing your arm, that's the point I think.)

The video showed that one of the martial artists (wearing sensory equipment) performing a punch, and it actually showed the muscle contractions starting at the feet, and traveling up the guys body as he twisted his hips into the punch, and right to the end of the fist at impact (which is how I was taught punching technique too, you don't make a tight fist until right before impact).

I think shudos really accentuate the kind of whip-like technique your muscles are capable of with this idea of a contraction propagating through your muscles.
Gelsamel Epsilon
Mar26-07, 10:58 PM
P: 316
A heavy hand (relaxed) hits harder then a light hand (tensed).

Physics+biomechanics of Aikijujustu would be extremely complex.
Mar29-07, 11:35 AM
P: 200
This thread reminded me of this safety flyer I got at UPS (where I work). It said force is equal to mass times distance, so you should keep your packages close to your body to reduce the force you'd have to exert.

Quote Quote by Gelsamel Epsilon View Post
A heavy hand (relaxed) hits harder then a light hand (tensed).
This doesn't sound right. I agree you should be relaxed before impact, but at impact (or right before it) you need to tense your hand. It's the difference between being hit with clay and a brick.
Mar29-07, 12:32 PM
P: 858
There was a quite interesting documentary on the National Geographic concerning the science behind martial arts entitled "Fight Science". Viewer discretion is advised.
Mar29-07, 03:47 PM
Sci Advisor
FredGarvin's Avatar
P: 5,095
Quote Quote by Moridin View Post
There was a quite interesting documentary on the National Geographic concerning the science behind martial arts entitled "Fight Science". Viewer discretion is advised.
I knew someone was going to reference that steaming pile of dung. It's not worth the film it was printed on.
Apr4-07, 11:07 PM
P: 42
There really is quite a lot of those material in this line of research in biomechanics. The problem is: whether we are doing it for the shake of purely biomechanical research or for martial art trainning. I have been a martial artist for more than 10 years and a certified instructor. However the physical aspect are not really applicable in real trainning unless we have to consider the biological aspect as well. For example, we have to consider the sweating of the person, which would keep reducing his/her body weight before we can assume how heavy the punch or kick he/she can launch.
Dec27-11, 07:09 PM
P: 5
There is a new book just published called Parting the Clouds: The Science of the Martial Arts. It is written by a fourth dan karate instructor who is also a Master of Science. It starts at the basics - Newton's Laws and the Conservation of Energy, Mass & Momentum - and goes through just about everything concerned with strikes and collisions. The book is complete with numeric examples of what it takes to break a board or which is more important - speed or mass - and quantifications on the highest force achieved or fastest punch or kicking speed. It's available on and the author is Grenville Harrop.
Dec27-11, 07:24 PM
P: 757

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