Wednesday, May 21, 2008

The Physics of Freerunning

Good news everyone, I am officially Dr. Dave! I spent the past few months writing my Ph.D. thesis and I successfully defended my dissertation. I apologize for not posting regularly, but I am sure you understand.

Thesis Break, Bond Style!
While I was writing my thesis, I would occasionally take a break and watch a movie. One of the movies I watched was Casino Royale, the most recent entry
in the James Bond franchise.

Chase scenes are standard in Bond movies and Casino Royale had its fair share. My favorite is when Bond pursues a bomb maker, Mollaka, on foot through a construction site in Madagascar.
Below is a link to the scene posted on YouTube. The clip is about 9 minutes long.

In this foot chase, Bond and Mollaka have two different styles. Mollaka is graceful and efficient; Bond is aggressive and haphazard. It is clear that Mollaka has an advantage over Mr. Bond. What's Mollaka's secret?

Free Running

S├ębastien Foucan, the founder of a sport called free runnin
g, played Mollaka. Free running is a sport that is dedicated to efficient motion between two points.

During the foot chase, Mollaka knew how to use his environment to keep him moving forward. While his jumps were very fancy to watch, he was clearly using the laws of physics to his advantage.

Rolling, Rolling, Rolling
I have seen similar acrobatic free running feats perform
ed during martial arts demonstrations. The core philosophy of many martial arts is to redirect energy and I imagine the same holds true for free running.A basic move taught in many martial arts is the roll. A proper roll is a useful move that is designed to dissipate energy in a fall or jump. Look at this YouTube video showing how rolls are done. The people in this video clearly know what they are doing. Please don’t try this at home without the proper equipment. You can easily injure yourself.

The examples toward the end of the video show why the roll is a great move–it helps the free runner maintain his forward momentum after a jump and places him on his feet.

The Physics of Going Splat
In the YouTube examples above, we can see how rolling is very useful to free runners. Let’s learn about the physics of this motion.

Let’s imagine we have a ball of pizza dough. What happens if you throw it against the wall? I would predict that it would go splat and flatten. Why? When the dough collides with the wall all the energy of motion–called kinetic energy– is instantly absorbed by the pizza dough.

Let's think about what happen in another example.
Now imagine that we roll the ball of dough on the ground towards a wall. What happens in this case? The ball of dough will gradually lose speed before hitting the wall. In this example, th
e dough is more likely to maintain its shape because the energy is lost gradually as it rolls rather than suddenly at impact.

In both cases, a similar amount of energy is lost. What matters most is the amount of time required for the dough to slow down. If it the dough stops suddenly, then it will flatten. If the dough slows gradually, it will retain its original shape.

Over the Handlebars
While pizza dough is a good example, let’s think about how this works on a human body. The following is a true story:

A friend of mine was riding his bike in the park. Suddenly, a child jumped in front of him, causing my friend to swerve and avoid the child. Unfortunately my friend hit a bench and went flying over the handlebars. Being a black belt martial artist, he instinctively curled up into a ball and rolled on the pavement; he rolled a few times before coming to a complete stop.

The Physics of Not Going Splat
My friend was able to avoid significant injury because was able to roll and gradually dissipate his kinetic energy. Can you imagine what would have happened if he landed hard onto the pavement?

His body would have suddenly impacted the ground and instantly absorbed all kinetic energy. If you have ever experienced a crash, then you know this is a painful experience.

In the example of pizza dough mentioned above, a direct impact caused the dough to lose its shape. On the human body, a sudden impact would cause significant injury, like cuts and bruises, even broken bones. Ouch!

Whether you are a martial artist or a free runner, the ability to move with proper technique helps to prevent injury. By understanding physics we now know why. Remember, it all boils down to how fast or slow kinetic energy is dissipated.

Dr. Dave