How much of an approximation are power measuring tools for martial arts?

[Username34]

For instance this Power Cube device.

Is it capable of reporting EXACTLY how hard Francis Ngannou punched, or will it be biased towards mass or speed and overestimate one of the components?

How "off" from the actual physics of reality do you expect such a tool to be? 5%? 10%? 20%?

 

[Vanadium 50]

EXACTLY

No. No instrument is exact. All have uncertainties.

Further "how hard they punched" is not a physical term. Force? Pressure? Impulse? Something else?

 

[russ_watters]

Is it capable of reporting EXACTLY how hard Francis Ngannou punched, or will it be biased towards mass or speed and overestimate one of the components?

How "off" from the actual physics of reality do you expect such a tool to be? 5%? 10%? 20%?

I don't think there's an accepted "actual physics" measure of how "hard" a punch is, so that device picks something and measures that. I'm speculating that it measures the displacement over time of a collection of strong springs or springy pads, and calculates energy and power from that. I'd expect it to be pretty accurate (<5% should be possible) for what it is measuring.

 

[dlgoff]

For instance this Power Cube device.

Is it capable of reporting EXACTLY how hard Francis Ngannou punched, or will it be biased towards mass or speed and overestimate one of the components?

How "off" from the actual physics of reality do you expect such a tool to be? 5%? 10%? 20%?

My daughter was in martial arts for many years. If I remember correctly, it really depended where she hit the target. IMO, I'd say 20% or more.

 

[russ_watters]

My daughter was in martial arts for many years. If I remember correctly, it really depended where she hit the target. IMO, I'd say 20% or more.

That sounds more like an inaccurate punch than an inaccurate measurement to me.

 

[dlgoff]

That sounds more like an inaccurate punch than an inaccurate measurement to me.

Trust me. She wasn't inaccurate. She could break 4 boards stacked together with one fist punch. Had to be accurate for that.

 

[Username34]

I don't think there's an accepted "actual physics" measure of how "hard" a punch is, so that device picks something and measures that. I'm speculating that it measures the displacement over time of a collection of strong springs or springy pads, and calculates energy and power from that. I'd expect it to be pretty accurate (<5% should be possible) for what it is measuring.

My question was regarding power.

 

[Username34]

My daughter was in martial arts for many years. If I remember correctly, it really depended where she hit the target. IMO, I'd say 20% or more.

This is brand new technology, so no not comparable.

 

[dlgoff]

"That sounds more like an inaccurate punch than an inaccurate measurement to me."
Well, I kept some of the boards she broke:

 

[berkeman]

She could break 4 boards stacked together with one fist punch.

Is this the same dainty daughter who likes flying planes upside down?

 

[dlgoff]

Is this the same dainty daughter who likes flying planes upside down?

Yes!

@berkeman
BTW. She is teaching 4 other girl students now that she is a CFI (Certified Flying Instructor)

 

[Username34]

I don't think there's an accepted "actual physics" measure of how "hard" a punch is

Why would mechanical power be a good enough definition?

 

[russ_watters]

Why would mechanical power be a good enough definition?

I don't love it, I think I'd prefer energy. @dlgoff 's daughter surely knows that it's energy that breaks a board, not power.

 

[russ_watters]

Trust me. She wasn't inaccurate. She could break 4 boards stacked together with one fist punch. Had to be accurate for that.

Look, I'm not trying to be a jerk about it, but you said she wasn't hitting the target at the same place every time.

 

[dlgoff]

I don't love it, I think I'd prefer energy. @dlgoff 's daughter surely knows that it's energy that breaks a board, not power.

Yes. You are correct.

 

[dlgoff]

Look, I'm not trying to be a jerk about it, but you said she wasn't hitting the target at the same place every time.

No. I said she had to be accurate. Meaning, she had to hit right in the center of the four boards. I saved a few of the boards she broke:

 

[jrmichler]

I said she had to be accurate. Meaning, she had to hit right in the center of the four boards.

That, and hitting hard enough while using her hand correctly. I once spent a fun afternoon showing friends how to punch out windows in an abandoned building that was being demolished. Hit (leather gloves required) hard enough with the correct knuckle, and the window shattered with no pain on my part. Hit not quite hard enough, or with the hand slightly out of position, resulted in pain and an unbroken window.

 

[Vanadium 50]

My daughter was in martial arts for many years.

Gives new meaning to the term "striking beauty".

 

[Username34]

How powerful do you guys think is on a powercube?

 

[berkeman]

Is it capable of reporting EXACTLY how hard Francis Ngannou punched, or will it be biased towards mass or speed and overestimate one of the components?

How "off" from the actual physics of reality do you expect such a tool to be? 5%? 10%? 20%?

Why would mechanical power be a good enough definition?

It may be helpful for you to do a Google search for helmet impact testing methods to see what-all is used for certifying helmet designs. The purpose of a helmet is obviously to protect the head from real-world impacts as much as possible, and they will use certain test techniques to quantify that protection level.

In a sense, you are asking the opposite question, but the helmet test standards are targeted at real-world impacts to the head that can cause damage to the person. Some of the test standards record the peak acceleration, but other tests use other techniques.

And since the motion of the head during impact also makes a difference for damage, it would probably be better if that test cube thing used a simulated head instead of being mounted rigidly. Just the Medic in me talking out loud...

 

[phinds]

"That sounds more like an inaccurate punch than an inaccurate measurement to me."
Well, I kept some of the boards she broke:
View attachment 330132

Yes, and you'll notice that all the boards are broken WITH the grain, which is actually pretty easy. The test is if you can break even one board across the grain. You are right, of course that she had to hit at or near the center to get maximum leverage on the board.

As far as I'm aware, no martial arts board breaking is every done across the grain.

 

[berkeman]

As far as I'm aware, no martial arts board breaking is every done across the grain.

What about the concrete breaking demos...

 

[dlgoff]

What about the concrete breaking demos...

She did a little of that, but if I remember correctly, she used a palm strike (heal of hand), not a knuckle strike.

 

[phinds]

What about the concrete breaking demos...

They don't have any grain direction. I'm not suggesting that martial arts breaking of stuff is fake or anything, just that wooden breaks are always with the grain.

When I took Tae Kwan Do about 100 years ago, I brought home some of the pine boards to show my kid. I broke three stacked together (supported at both ends but not in the middle) and he was impressed.

Then I took the one I had put aside, which I could tell was the weakest of the lot, and I broke it just by gripping my fingers over the edges and then pressing the center with my thumbs. I am not particularly strong. I was showing him how pine boards break with the grain very easily.

Then I took one of my own that I had cut to the same length as the others but with the grain running along the length, not cross-grain, and smashed it in the center with a sledge mallet and all I did was dent it.

My lesson for him was not about martial arts, it was a graphic demonstration of the differences in wood strength across the grain and with the grain.

 

[berkeman]

When I took Tae Kwan Do about 100 years ago

I found this cute picture of you when you were just a puppy in that class.

https://www.karatemart.com/karate-dog-costume

 

[phinds]

I found this cute picture of you when you were just a puppy in that class.

View attachment 330137
https://www.karatemart.com/karate-dog-costume

I'll be damned. I didn't know cameras had even been invented back then

 

[Username34]

It may be helpful for you to do a Google search for helmet impact testing methods to see what-all is used for certifying helmet designs. The purpose of a helmet is obviously to protect the head from real-world impacts as much as possible, and they will use certain test techniques to quantify that protection level.

In a sense, you are asking the opposite question, but the helmet test standards are targeted at real-world impacts to the head that can cause damage to the person. Some of the test standards record the peak acceleration, but other tests use other techniques.

And since the motion of the head during impact also makes a difference for damage, it would probably be better if that test cube thing used a simulated head instead of being mounted rigidly. Just the Medic in me talking out loud...

Which is more crucial for power in terms of baseline mass - a heavy fist (big bone density) or a heavy arm with regular sized fist? Francis Ngannou has very big arms but his fist can't compare to this guy..