Cutting edge feet


Robert Howard can slice tiles and wooden planks with his hands and feet. So how does he do it, asks CLAIRE O’CONNELL

SMASH! The stacked roof tiles shatter into smithereens as Master Robert G Howard’s hand chops through them. Blocks of timber don’t fare much better either as he breaks them into pieces with his fists and feet.

From where I’m standing (a little scared, actually, but full of respect) it doesn’t look as if a human hand or foot should be able to break such impenetrable-looking objects, but Howard assures that the laws of physics say they can.

I believe him too, and it’s not just because I don’t want to argue with someone who has just broken a pile of roof tiles in front of me without flinching.

It’s because Master Howard not only has a seventh degree black belt in Taekwondo (he was the youngest person in Europe to achieve that level) but he’s also Dr Robert Howard, a lecturer at Dublin Institute of Technology’s school of physics.

Before he explains any of the physics behind the punches and kicks though, Howard sets down a few ground rules. Above all, martial arts in general – and Taekwondo especially – is about self-defence.

“If you are in trouble walk away if you can,” says Howard, who has been practising Taekwondo for over 30 years and whose father is also a Master.

“If you can’t walk away you might have to talk your way out. And if all else fails you use Taekwondo, which is about maximising your body to defend yourself – and that’s related to the physics.”

Taekwondo training involves perfecting patterns of movements (including kicks, turns and punches) and sparring with protective pads. Then you eventually break concrete and timber to demonstrate that your strikes are forceful enough to injure.

So how does physics help you deliver a good punch or kick? It’s down to mass, velocity and positioning, explains Howard.

“The purpose of a strike in self-defence is not to push the bad guy away but to maximise damage, and that involves deformation,” he says.

The deformation energy on impact determines just how damaging that impact is, and factors that affect it include your mass and velocity.

Physics tells us that to pack more power into the punch you increase mass and velocity. So by moving your body forward into the punch, rather than just extending your arm, you can really bump up the deformation energy.

Think about a small rock hitting a can: when the stone smacks into the metal, the rock will most likely lose velocity.

“Ultimately the kinetic energy before the collision has to be the same as the kinetic energy after the collision,” says Howard. “If there’s some missing where has that gone? When it hits the object it might not move as fast, and the energy went into deforming the can.”

A well-executed punch can have a force of almost 5,000 newtons on impact, explains Howard, who puts it into context: “That is the same as the weight of a cow on your head. So you could either punch the bad guy or drop a cow on them if you had it handy.”

He also compares it to the force needed to break a bone, such as a rib, which comes in at around 3,000 newtons. But thankfully he’s not about to demonstrate on a human; instead he smashes some timber and tiles to simulate.

So why don’t his bones break in the process? Positioning is key, he says. “I can chop those tiles but I could also trip over them and break my wrist,” he says.

“So the position of the hand or foot when you strike is important: the muscles need to be tense and the bones need to be straight.”

At this point I’m relieved that Taekwondo instructs practitioners to use their skills with respect and courtesy.

“Whether you are a physicist doing high-level experiments or a martial artist defending yourself, it’s important to remember that with great power comes great responsibility,” he says.

“There’s a potential to do damage to people, so it’s important to take that responsibility seriously.”

Oh and another rule: sweep up the bits of roof tile when you are done.

For more on Taekwondo see the Republic of Ireland Taekwon-Do Association website,