In the 64th minute in a match against Juventus on Tuesday, Cristiano Ronaldo of Real Madrid executed a breathtakingly powerful bicycle kick over his head that he later called his “best goal.” Hurling himself high into the air and rapidly scissoring his right leg upward, his shoelaces met the ball just in time to kick it past Italian goalkeeper Gianluigi Buffon. The notoriously difficult move was, for many reasons, a superhuman feat of physics.
What sets the bicycle kick apart from the other kicks used in soccer is that, because the player’s body is so high up off the ground and is angled upward, there is a greater distance for the leg to kick — and, therefore, more opportunity to gain momentum. Generally, the speed of the leg is a key part of the force that’s applied to the ball when it is kicked. In the case of the bicycle kick, the leg moves so fast that once it meets the ball, the distance the ball can travel is exceptionally far, and the speed that it reaches is exceptionally fast. (It certainly helped that Ronaldo’s kick was aimed at the back right corner of the goal.)
In 2007, an episode of the long-running FSN show Sport Science calculated exactly how quickly a professional player’s leg might move as a result of the various motions involved in a bicycle kick. Experts on the show measured one of the most revealing variables involved in the physics of a bicycle kick: the angular velocity of the leg, which measures how fast the kicking foot rotates around the body.
The bicycle-kicking legs of Major League Soccer player Jason Hernandez, they explain, are like the blades of a helicopter, in that it rotates around a single axis. Physiological constraints make it impossible for Hernandez’s leg to do a 360, like a helicopter, of course, but the basic principle is the same.
Before measuring the angular velocity of Hernandez’s leg, they flip him upside down using a harness in order to remove the effects of gravity. Without gravity pulling him downward, he has room to maximize the range of motion of his kicking leg. With the ball over his head, he jerks his body upward, and with it goes his leg. Taking into account the movement of his leg as well as the rotation of the body itself, the path the leg travels is much longer than the path it would take on the ground.
Think of it as the hands of a clock: If in a regular kick, a player’s leg moves from 4:00 🕓 to 7:00 🕖, a bicycle kick allows a range of motion that’s far more like moving from 4:00 🕓 to 12:00 🕛.
They calculated that Hernandez’s leg moved at a speed equivalent to 300 revolutions per minute — which is roughly the same speed at which a helicopter’s wings rotate.
In short, the expanded range of motion afforded by a bicycle kick allows the body to build up more momentum, which in turn ultimately increases the force applied to the ball. Of course, the ability to get the sort of air that allows your body to move like that is one that only the most athletic among us can do.
“This One Was Spectacular”
Even Ronaldo, after his kick, was stunned by what he had done. “I had also scored another one similar, but I have to say, this one was spectacular,” he said. “I jumped very high and obviously it’s a goal that will live long in the memory.”