The science behind lacrosse skills

On Tuesday night I faced some considerably large fears and stood up on stage to do a 9-minute science related set for Science Showoff. The subject? The science behind some skills from lacrosse. Here is a blog post based on the set.

Men’s and women’s lacrosse are quite difference sport. The men’s games is essentially ice hockey rules on a field – the men wear pads and can hit each other – whereas the women’s game is technically a non-contact sport. Although, I do have the bruises to suggest otherwise!

"Ball players" painted by George Catlin

The modern game of lacrosse is based on stick ball games played by Native American tribes. It was given its name by a French Jesuit missionary who saw the Iroquois tribes playing in 1637. La crosse simple means “the curved stick’! However, I think that the names which the native tribes gave the game are a little more fun. Translated examples include “men hit a rounded object”, “bump hips” or “little brother of war”.

This last name indicates that, apart from just being a sport, lacrosse had a more serious role for these tribes; it was often played as training for battles and was used as a way to settle tribal disputes. It is rumored that the goals could be miles apart and sometimes the ball was actually the head of defeated past enemies!

It was believed that the game was supernaturally controlled, and that good players were in the favour of the gods. But, whereas the original game might have been more due to luck and sheer athleticism that made people think there was some unknown force involved, the modern game definitely isn’t supernaturally controlled. There is some very basic science behind lacrosse skills.

I’ve taken 2 keys skills that are essential for both the men’s and the women’s game and briefly explained the science behind them.

Diagram illustrating centripetal force

First up is how to keep the ball in the lacrosse stick. If you were to carry the stick horizontally then the ball is exposed, and anyone could hit the stick and knock the ball out. Also, you cannot pass the ball when the stick is horizontal. However, if you were to run along with the stick vertically then it would just fall out. Some kind of force is needed to keep the ball in the stick.

If you take a ball on a string a swing it round then the string exerts force on the ball perpendicular the motion of the ball and forces it to move in a curved path. In lacrosse instead of a string, the lacrosse stick is moved so that it exerts force on the outside of the ball, a centripetal force, and results in the ball sitting safely in the stick. This is called cradling.

Player cradling and keeping ball in sweet spot of the stick - Syracuse University attacker Megan Mosenson advances the ball against Louisville midfielder Aimee Dixon in the first half of their game Friday at the Carrier Dome in Syracuse. Jim Commentucci / The Post-Standard

 

 

A good player will find the optimum amount of force to exert on the stick, enough so that the ball will continue to sit in the sweet spot of the stick and not fall out, but not too much so you are not frantically cradling and not able to do anything else!

The next skill I wanted to show the science behind was the fake pass. Why do we flinch or react when someone fakes throwing a pass? It’s actually to do with the way that the brain constructs what we perceive as reality; our eyes actually aren’t fooled when someone fakes a pass, it’s our brains that are.

When I move my body and my stick in a certain way, past experience dictates that the ball is likely to be coming in your direction very fast. I’m creating visual cues which your brain constructs a reality from. What is interesting is which different types of visual information are important to you and what isn’t.

 

 

 

Here are some pictures of a magicians performing a magic trick. He simulates a coin being thrown from one hand to another when it actually remains in his right hand (as shown by the red circles).

From Cui et al 2011

Stephen Macknik and Susana Martinez-Conde used a clip of the above trick (and others) to carry out an experiment to test whether social cues, such as where the magician was looking, or implicit motion cues, the body movements, were more important in tricking the brain. They showed the clip normally to half the volunteers, and to the other half they showed them with the magician’s face covered.

Screen shot taken from Cui et al 2011

They asked the volunteers whether they perceived the coin as disappearing and also fitted them with eye-tracking devices to see where people were looking during the clips. The group found that the volunteers did not look at the magician’s face, whether it was occluded or not. Instead, they look predominantly at the magician’s hands. They also showed that the presence of the magician’s face did not enhance the illusion. They concluded that the social cues are sometimes not necessary to sell the fake.

Example of eye-tracking data from Cui et al 2011

I sent Stephen and Susana some YouTube clips of people doing fake throws and shots in lacrosse and they suggested that, due to the player often being in motion and due to the large movements involved in the fake, the implicit motion cues would be dominant over the social ones.

So by understanding how the brain constructs reality, you can learn how to trick it and use it to ‘sell’ a good fake. Using fake passes and fake shots allows you to trick you defenders or the goalie and puts you at an advantage. It really works, as shown in this YouTube clip (sorry for the bad copy!)

 

 

So there you go, two bits of basic science to explain two essential lacrosse skills!

Source: Cui J, Otero-Millan J, Macknik SL, King M and Martinez-Conde S (2011) Social misdirection fails to enhance a magic illusion. Front. Hum. Neurosci. 5:103

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