Goalkeepers Limited By Human Visual System In Free Kick Situations

You’ve aligned your wall just right, positioned yourself in the sweet spot between the sticks, your opposition steps up to take the free kick. He/she strikes it with such cunning efficiency that it spins into the net with smashing force, leaving you standing, looking on dumbfounded. Been there before? Yes, every goalkeeper has. Strikers like David Beckham and Cristiano Ronaldo are such masters in the art of the free kick situation that they utilize limitations (knowingly or not) in the human visual system ruthlessly to their advantage.

Rocket-like Ronaldo Free Kick Makes Mockery of Sunderland’s Craig Gordon

When Manchester United played Sunderland the other night, Ronaldo’s free kick was struck with such accuracy and speed, that it left Craig Gordon, firmly planted to the ground, unable to do anything but watch on in confusion. Following are some video highlights of the game between Manchester United and Sunderland (study Ronaldo’s goal and take some notes):

Phycisists Insights Into Why The Best Free Kick Takers Are So Efficient

This recent Times Online article discusses some of the reasons why goalkeepers are at a serious disadvantage when it comes to the free kick situation. One important suggestion in the article pointed to the mechanics behind David Beckham’s kicking style during a free kick:

“Beckham’s run-ups are longer and from an acute angle, which allows him to generate extra spin and control as he massages his instep around the ball, striking it well wide of the centre to send it spinning.

Why is Beckham so effective? Talent, practice and the Magnus force. That is the name for the effect by which spin reduces the air pressure on one side of the ball and increases it on another, making it swerve.

Physicists have estimated that over 30 metres, a ball can deviate upwards or sidewards from its normal straight course by as much as four metres. Dr Ken Bray, a sports scientist at the University of Bath, found that Beckham kicks the ball at 70mph and makes it spin ten times a second. By angling the spin direction, Beckham pulls the ball down as well as across, using top spin, like a tennis player, so the ball slows and dips. “

Compelling Study Shows Limited Human Visual System Limits Goalkeepers Ability To React To Free Kick Situations

Early last year I came across an article , that pointed to the limitations in our human visual system, and phenomenon such as Magnus Force (as stated in the article above). Utilizing precise technique, and the dynamics of the modern ball, players like Ronaldo play on the limitations in our own visual systems and perception.

Springer (2020, May 19). Eyeballs Vs Footballs: Limitations Of Human Visual System Hinders Goalkeepers From Predicting Free Kicks, published a fantastic article that studied 11 players from AC Milan, Olympique de Marseille, Bayer Leverkusen and Schalke 04 (9 of whom were goalkeepers) who were asked to judge whether a simulated free kick would end up in the goal or not using a modern virtual reality system.

“The viewpoint was fixed in the centre of the goal. When there was no spin, balls arriving directly opposite the goal were consistently judged to be entering the goal.

When the ball was spinning clockwise, the resulting trajectories – from the point of view of the goalkeeper – unfolded on the right-hand side of the no-spin trajectory, resulting in a goal only if the striker shot from left of the central position in front of the goal.

For conditions where the ball was spinning counter-clockwise, the balls landed in the goal only when they – from the view of the striker – were kicked from the right-hand side of the no-spin trajectory. There was no difference between the judgements of the field players and goalkeepers.”

Notes To Take Away From The Above Studies

The above findings show that there are inherit deficiencies in the human visual system that make it difficult for goalkeepers to judge the arrival point of a ball being kicked in a shooting situation subject to an additional “accelerated” influence (AKA…Ronaldo or Becks kicking the crap out of the ball with blinding force). So there are a few things to take away from all of the above jargon. Free kick situations are profoundly effected by:

• Trajectory and power of the shot.
• Phenomenon called the Magnus force, where a ball spinning around an axis, gives rise to an acceleration that is perpendicular to the direction of the ball. This causes a lateral deviation in the ball’s trajectory.
• Deviation of the ball (up, down and sideways) when it is struck from a distance (such as a free kick situation) and deviates from it’s normal straight line path.
• New technology in the modern ball that are aerodynamically efficient compared to previous overly panelled and stitched footballs making the ball faster in it’s trajectory over a longer distance.

So, often times than not, although seemingly to the public eye, a goalkeeper looks like a stunned mullet when they’ve let one slip by into the net during a free kick situation. Scientifically, we see that there are limitations in our own visual systems that make it difficult at times for goalkeepers to interpret when to attack the ball effectively.

Don’t be glum about not getting to the ball on time for a save when it comes to the free kick situation, as they say, practice makes perfect, and I’m certain that over time a goalkeeper can edge out indespcrepencies (not totally of course) in their own visual perception via repetitive training and a close study into the physics of the ball and the way in which top flight stars manipluate these situations to their advanatage.